หน้าหลัก Quarterly Review of Biology A Critical Evaluation of the Ontogeny of Human Sexual Behavior

A Critical Evaluation of the Ontogeny of Human Sexual Behavior

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A Critical Evaluation of the Ontogeny of Human Sexual Behavior
Author(s): Milton Diamond
Source: The Quarterly Review of Biology, Vol. 40, No. 2 (Jun., 1965), pp. 147-175
Published by: The University of Chicago Press
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A CRITICAL EVALUATION OF THE ONTOGENY
OF HUMAN SEXUAL BEHAVIOR
BY MILTON

DIAMOND

Department of Anatomy, University of Louisville School of Medicine, Louisville
ABSTRACT

The classical view of human sexuality holds that man is invested with a particular
sex within which he, as an individual, develops. Recent attempts to alter this conception and to explain psychosexual maturation as developing from a neutral rather than
a sexual base are here reviewed and criticized.
Essentially, a psychosexual neutrality-at-birth theory holds that male and female
patterns of sexual orientation and behavior are attributable exclusively, to learning or
imprinting phenomena. This theory is derived from clinical observations of individuals
manifesting morphological sexual incongruities (hermaphrodites, pseudohermaphrodites, etc.).
This article defends the view of inherent somatic sexuality organizing man's psychosexual development by: (a) reviewing man's place ; on the evolutionary continuum, and
the broad base of sexual behavior within which this discussion must be considered;
(b) presenting normative, clinical and anthropological evidence inferring a particular
sexual predilection at birth; (c) showing genetic, hormonal, and neural indications for
sexual predisposition; (d) refuting the extent of imprinting inzpolved in humans; and
(e) showing the futility of separating "nurture" from "nature" in reference to the
role of learning and acquisition of a gender role.
of various individuals with sexual abnormalities.
Particular attention was given to those patients
classified as sexually precocious or as hermaphroditic.

INTRODUCTION

A

review of the many areaspertinent

to the field of sexual behavior over
the last decade reveals the development and elaboration of various
psychosexual medical aspects. This
in itself is not surprising in view of the greater
all-round interest in the psychological field
coupled with the increased publicity given to
studies bearing on sexual behavior. What is
surprising, however, is a certain direction this
development has taken and the relative ease
with which one view has been accepted.
Starting in 1955, articles written by John
Money and Joan and John Hampson, either
in collaboration or separately, began to appear
with regularity. Within two years these investigators had produced a book and almost
a dozen papers (see list of literature). The
content of their articles details clinical examinations, descriptions, interviews, and therapy

The term "hermaphroditic" is broadly used
here to indicate sexual deviance from the normal
condition in any two or mo,re of the following
ways: (a) external genital morphology; (b) internal accessory reproductive structures; (c) hormonal sex and secondary sexual characteristics;
(d) gonadal sex; and (e) chromosomal sex.
This work must be considered of value in
giving new insight into various clinical areas
previously almost taboo, and in shedding light
on some particularly intriguing questions of
human sexuality.
The articles went further,
however, into theorization about the ontogeny
of human sexual behavior and its modifiability,
and included a reappraisal of classical notions
of sex roles. Probably on the strength of the
clinical aspects, this revised theory seems to

147

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148

THE QUARTERLY REVIEW OF BIOLOGY

have gained favor and gone without serious
challenge.
Essentially the theory advocated by Money
and the Hampsons holds that gender role
all those things that a person says or does to
disclose himself or herself as having the status
of boy or man, girl or woman, respectively,
and sexual orientation as a male or female
is independent of chromosomal sex, gonadal
sex, genital morphology, hormonal balance, or
other commonly used indicators of sex (Hampson and Hampson, 1961; J. L. Hampson, 1964).
In their own words:
. . . in place of a theory of instinctive

mas-

culinity or femininity which is innate, the
evidence of hermaphroditism lends support
to a conception that psychologically, sexuality is undifferentiated at birth and that it
becomes differentiated as masculine or feminine in the course of the various experiences
of growing up (Money, Hampson, and Hampson, 1955b).
Now it becomes necessary to allow that
erotic outlook and orientation is an autonomous psychologic phenomenon independent
of genes and hormones, and moreover, a
permanent and ineradicable one as well
(Money, 1961e).
It is more reasonable to suppose simply
that, like hermaphrodites, all the human race
follow the same pattern, namely, of psychosexual undifferentiation at birth (Money,
1963a).
Thus, in the place of the theory of an
innate, constitutional psychologic bisexuality . . . we must substitute

a concept of psy-

chologic sexual neutrality in humans at birth
(Hampson and Hampson, 1961).
In brief, their theory may be called a psychosexual "neutrality-at-birth" theory, as opposed to a "sexuality-at-birth" theory. Although
other investigators have supported and projected evidence and theory of a similar nature,
the present focus is placed on the works originating from the authors just cited, since they,
starting almost with a formal challenge to the
classical concept of human sexuality (Money,
Hampson, and Hampson, 1955b), are perhaps
at present most closely associated with this
approach and most prolific and influential in
this area of thought, particularly in regard to
clini-calconsiderations.
It is my present intention to review the
evidence relative to this theory, and to suggest
in contradistinction that the very same data may

not be inconsistent with more classical notions
of inherent sexuality at birth. This inherent
sexuality, like other biological characters, need
not necessarily manifest itself at birth as it
might be first revealed at puberty or during
adulthood. Nevertheless, inherent sexuality may,
from birth, provide a built-in "bias" with which
the individual interacts with his environment.
Generally the concept of psychosexual neutrality at birth may be considered to draw support from the following three broad areas: (1)
clinical cases; (2) the imprinting phenomenon;
and (3) learning theory. The clinical material
will be considered first, as it has figured most
prominently in the formation and presentation of this theory, Wherever possible, counterevidence will be drawn primarily from human
data.
CLINICAL
ENCE

EVIDENCE
OF SEXUAL

IN SUPPORT
NEUTRALITY

OF THIE EXISTAT BIRTH

The basic arguments in favor of a psychosexual neutrality-at-birth theory are derived
from clinical investigations by Money, Hampson, and Hampson with patients manifesting
various sexual anolnalies. Each patient was
rated in regard to the usual criteria of sex assignment, namely, gonadal sex, hormonal sex,
chromosomal sex, and internal and external
genitalia. In addition, these patients were rated
as to the assigned sex in which they were reared
and their gender role. Each of the first five
categories was separately compared with the
last two, and the last two were compared with
each other.
Gonadal Sex
Among 20 patients in whom a contradiction
was found between the gonadal sex and the sex
of rearing, 17 disclosed themselves in a gender
role concordant with their rearing. The gonadal
structure was an unreliable prognosticator of
such an individual's gender role (Money, Hampson, and Hampson, 1955b).
Hormonal Sex
Of 27 patients whose hormonal functioning
and secondary sexual body morphology contradicted their sex of rearing, 4 became ambivalent with respect to gender role as male
or female, but 23 of them established gender

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ONTOGENY OF HUMAN SEXUAL BEHAVIOR
roles consistent with their sex of rearing despite the embarrassment and worry occasioned
by such contradictions (Money, Hampson, and
Hampson, 1955b).
Chromosomal Sex
Without a single exception among 20 patients, it was found that the gender role and
sexual orientation were in accordance with the
socially assigned sex and rearing rather than
in accord with the chromosomal sex (Hampson
and Hampson, 1961).
Internal and External Genitalia
In 22 of 25 individuals, the gender role
agreed with the assigned sex and rearing and
was not in accord with the predominant male
or female internal accessory structures (Hampson and Hampson, 1961). And in cases where
the sex of rearing was contradictory to the sex
of the external genitalia, 23 of 25 individuals
had been able to come to terms with their
anomalous appearance and to establish a gender role consistent with their assigned sex and
rearing (Hampson and Hampson, 1961).
Assigned Sex and Gender Role
Despite the extent of the various sexual
anomalies and incongruities involved, only 8
of 131 comparisons (6%) did not show concordance of assigned sex and gender role. It
seems that the best indication of psychosexual
orientation (gender role) for hermaphroditic individuals is the sex of initial parental assignment. This would be a better index than
chromosomal sex, gonadal sex, or any other of
the five standard criteria of sex dimorphism
(Hampson and Hampson, 1961).
Conclusions and Comments
The conclusions drawn from evidence such
as that cited above are perhaps stated most
succinctly by Money, Hampson, and Hampson
(1955b) as follows:
In the light of hermaphroditic evidence, it
is no longer possible to attribute psychologic
maleness or femaleness to chromosomal, gonadal or hormonal origins, nor to morphological sex differences of either the internal
accessory reproductive organs or the external
genitalia.

. .

. From

the sum total

of her-

maphroditic evidence the conclusion that
emerges is that sexual behavior and orien-

149

tation as male or female does not have an
innate, instinctive basis. In place of a theory
of instinctive masculinity or femininity which
is innate, the evidence of hermaphroditism
lends support to a conception that psychologically, sexuality is undifferentiated at birth
and that it becomes differentiated as masculine or feminine in the course of the various experiences of growing up.
During these experiences of growing up the
normal human is assumed [from hermaphroditic
(pathological) data] to be imprinted as well
as taught a sexual role. The first 2- or 3
years of life are supposedly the critical period
for human imprinting, and cases are cited
where alteration of sex after this age is traumatic (Money, Hampson, and Hampson, 1955a,
1956, 1957; Hampson and Hampson, 1961;
Money, 1961e). This age is correlated by
Money with the development of verbalization.
He believes that the critical period for the
imprinting of gender role and orientation corresponds with a critical period for the establishment of a native language. Another critical
period for limited modification of gender imprints is postulated to occur at puberty (Money,
1961e). To further the idea that a psychosexual
imprint is fixed and irreversible, 5 cases of
genetic females born with fused labia and enlarged clitorides are cited. Two of these were
reared as boys and three as girls, and yet all
seemed to be psychologically content in their
present sex (Hampson and Hampson, 1961).
The extent and depth of the imprint and
subsequent learning is supposedly such that alteration after 4 years of age is fraught with
psychological danger and is usually unsuccessful (J. G. Hampson, 1955, 1964). "With only
1 exception the 6 patients reassigned later than
the first birthday were rated as inadequately
adjusted" (Hampson and Hampson, 1961).
Given the evidence presented, what may we
conclude? It has been shown that hermaphroditic individuals in our society find it possible
to assume sexual roles opposite to their genetic
sex, morphological sex, etc., and they can assume this role so well that they can function
socially as "normal" members of society, engage in erotic activities, and receive pleasure
in their reared roles. To best assume this role
it is most advantageous in our society for them
to start early in life, preferably before the first
birthday. Beyond these conclusions, however,

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THE QUARTERLY REVIEW OF BIOLOGY

150

much has been extrapolated. Maybe it has been
that humans, particustrongly demonstrated
larly hermaphroditic ones, are flexible when it
comes to the assumption of an incongruous
sex role. Yet to assume that a sex role normally is exclusively or even mainly a very
elaborate, culturally fostered deception and imand that it is not also
printing phenomenon,
reinforced by taboos and potent defense mechanisms superimposed on a biological prepotency
or prenatal organization and potentiation seems
unjustified and, from the present data, unsubstantiated.
CONSIDERATIONS

REGARDING

SEXUALITY

INHERENT

AT BIRTH

Any theory has to contend with various types
of data. Whereas the theory of psychosexual
neutrality-at-birth is primarily derived from observations of clinical deviations from the normal, there is not only clinical but anthropological, and multidisciplinary experimental evidence
for the existence of psychosexual sexuality-atbirth.
of such data,
Before further consideration
the following two points are to be regarded as
fundamental:
(1) It should be readily obvious that man and
his behavioral parameters follow the natural
scheme of evolution, although it is often difficult to apply animal data to man. In the face
of abundant evidence that nonhuman species
as well as morphologically
are behaviorally
fixed in a particular sex at birth, a "neutralityat-birth" theory would indirectly
infer that
man's sexual behavior patterns are different
from those of all other vertebrates by not being
instinctively mediated.
Because they are often confused and misused,
the terms "innate" and "instinct" are defined for
use in this paper as follows: "Innate, a term
applied to differences in genetic character between two members of the same species that have
been raised in the same environment. (It is now
generally acknowledged that the term innate, a
technical one in genetics, cannot properly be
applied as synonymous with unlearned or inborn,
and its use in that sense may be expected to
become less frequent. Where it has appeared in
the past, innate behavior should now be read as
unlearned behavior or species-specific behavior)."
(Verplank, 1957).

"Instinct, a hierarchically organized nervous
mechanism which is susceptible to certain priming, releasing, and directing impulses of internal
as well as external origin, and which responds to
these impulses by coordinated movements that
contribute to the maintenance of the individual
and species." (Tinbergen, 1951).
I will hold that man in regard to his sexual
behavior patterns is, like all other vertebrates,
subject to prenatally organized mediation. The
manner or extent of this mediation is not yet
clear but is believed to involve the fetal organization and potentiation of certain neural
tissues which are, within genetic limits, postnatally modifiable but not to the extent of
complete reversal or negation. This effect on
the nervous system is believed primarily to
be a function of the genetically induced endocrine environment of the presexually differentiated individual. For man as well as most
other vertebrates this is a prenatal occurrence.
Ontogenetic experiences are superimposed on
this potentiated nervous system and serve to
give emphasis and further direction to predisposed tendencies. Man is probably more flexible in regard to this organization than any
other species, but that would not justify our
saying he is free of it.
(2) It is significant that no criteria or definition of human male or female behavior has
found universal acceptability. Humans, as well
as many other species of animal, normally exhibit elements of sexual behavior usually attributed to members of the opposite sex. The
capability and frequency of such behavior is
neither rare nor bizarre. I will defend the
point, that although humans can adjust to an
erroneously imposed gender role, (a) it does
not mean that prenatal factors are not normally
influential, and (b) they do so with difficulty
if not prenatally and biologically predisposed.
Beach in a lecture given at Yale in 1948
pointed out that:
. . .laws are violated by the homosexual individual but to describe his behavior as
'unnatural' is to depart from strict accuracy.
The zoological evidence shows that female
mammals frequently display masculine coital
behavior when confronted with sexually receptive members of their own sex. This
has been observed in more than a dozen
species and undoubtedly occurs in many
The physiological
others not yet studied. .

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ONTOGENY OF HUMAN SEXUAL BEHAVIOR
mechanisms for feminine sexual behavior are
found in all males and those for masculine
behavior exist in all females. The same stimuli that elicit feminine copulatory reactions
in the female will, under appropriate conditions, produce similar reactions in many
males; and the stimulus configuration evoking masculine responses in males is the one
which most effectively calls forth these same
responses on the part of the female. Human
homosexuality reflects the essential bisexual
character of our mammalian inheritance. The
extreme modifiability of man's sex life makes
possible the conversion of this essential bisexuality into a form of unisexuality with the
result that a member of the same sex eventually becomes the only acceptable stimulus to
arousal.
Human sexual life is not unique in its susceptibility

to modification.

. .

. (Beach, 1948a

[emphasis added.] ).
Kinsey and colleagues, indeed, report various varieties of heterosexual and homosexual
activities as not uncommon either for males
or for females (Kinsey, Pomeroy, and Martin,
1948; Kinsey, Pomeroy, Martin, and Gebhard,
1953).
Thus, both normal human beings or hermaphrodites who exhibit various so-called anomalous sexual behavior still are performing within
the biological continuum predictable by evolution. Evolving from a highly stereotyped pattern among primitive organisms, humans are
capable of displaying highly flexible sexual behavior patterns. An evolutionary trend starting
with inflexible stereotyped sexual behavior and
progressing to flexibility in behavior is consistent with modern genetic and evolutionary
concepts (Tax and Callender, 1960). The very
considerable extent of this flexibility, particularly in hermaphrodites, may account for the
many cases of maintained gender role which
atre incompatible with morphological criteria
of sex. This same flexibility may account for
the erroneous theory of psychosexual neutrality
for normal individuals.

151

in a malassigned sex past the age of four, these
individuals are supposedly unable to negotiate
a change in their gender role without severe
emotional trauma (Hampson and Hampson,
1961). The neutrality theory is supported by
no normative data. A theory that psychosexuality exists at birth, on the other hand, can use
the same evidence and demonstrate (a) that humans, hermaphrodites in particular, are flexible
enough to maintain an atypical gender role,
either by choice or accident, even when contradictory to their normal external genitalia;
(b) that a gender role, if malassigned may be
reassigned after the age of four without undue
trauma; and (c) irrespective of the foregoing
conclusions, that normal as well as hermaphroditic individuals are predisposed toward a
particular gender role at birth.
Studies of Normal Children

Although the literature is scanty in this regard, various studies of neonatal, preverbal, and
preschool children indicate that there are differences which may be considered indicative
of sexual differences existing from birth and
which are psychosexually predisposing to adult
nale or female roles.
Terman (1946), in an extensive review of
normal psychological sex differences in children,
wrote: "Sex differences have been found for
almost every physical variable, including body
build, gross and fine anatomy, physiological
functioning and biochemical composition. Indeed, every cell in a human body bears the
stamp of its sex." He then proposed that
some of these differences, such as height, weight,
body build, strength, endurance, motor ability,
and rate of maturation, might be expected
to reflect themselves behaviorally. In this regard he lists the following: (a) Body Size.
The mean weight of boys at birth exceeds that
of girls by approximately 5 per cent and their
body length is greater by 1 or 2 per cent.
This superiority continues until about the age
of 11. (b) Vital Capacity. As one of the deAT BIRTH
EVIDENCE IN SUPPORT OF SEXUALITY
terminers of the sustained energy output which
The evidence presented in support of the is possible for an individual, vital capacity
concept of psychosexual neutrality-at-birth pri- may considerably influence sex differences in
marily involves hermaphroditic individuals who play interests, and other activities. Boys show
have successfully adapted themselves to an as- a 7 per cent superiority in vital capacity by
signed gender role inconsistent with one or age 6 and rapidly increase their lead to about
more morphological criteria of sex. Once reared a 35 per cent superiority at age 20. (c) Mus-

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THE QUARTERLY REVIEW OF BIOLOGY

152

cular Strength. Tests of strength in grip, back,
and legs show boys to be superior at all ages
tested. At age 7 boys show about 10 per cent
superiority and this increases to a 50 to 60
per cent advantage at age 18. (d) Rate of
Maturation. It is widely recognized that girls
generally exhibit more rapid physical development than boys. In skeletal development girls
are superior to boys at birth and increase
this superiority at a fairly steady rate until
growth is complete. "Girls of all races precede boys on the average by twelve to twenty
months in pubertal development, and their
adolescent growth changes are correspondingly
accelerated."
These obvious examples of constitutional differences are reflected in the individual choice
of the more muscular forms of behavior of male
children, such as running, climbing, and wrestling, compared with the more conservative and
sedentary activities of female children, such
as hopping and skipping. This was extensively
reported by Lehman and Witty, as early as
1927, in a classical study involving some 19,000
children. Walker (1962), studying the somatotypes and behavior of preschool children 2 to
4 years old, has presented much data to indicate that there is a good correlation between
sex-related behavior traits and body build as
rated by endomorphy, mesomorphy, and ectomorphy. He concludes that "in this group
of preschool children, important associations do
exist between individuals' physiques and particular behavior characteristics. Further, these
associations show considerable similarity to those
described by Sheldon for college-aged men,
though the strength of association is not as
strong as he reports. It is suggested that the
relations are multiple determined, arising from
primary body conditions (e.g., strength, energy,
sensory

thresholds).

. .

. In

particular,

varia-

tions in physical energy, in bodily effectiveness
for assertive or dominating behavior, and in
bodily sensitivity appear as important mediating links between physique structure and general behavior."
In areas such as conation and cognition we
also note early manifest sex differences. This
is especially significant, since these categories
are believed to reflect traits less influenced by
culture. There is considerable evidence that

from early childhood boys show more aggression and anger than girls. Goodenough (1931)
reported this to be manifest as early as 7
months of age. In regard to personality Walters, Pearce, and Dahms (1957) have demonstrated that 2- to 5-year-old girls are significantly more friendly, sympathetic, and helpful
to others ("affectionate") than are boys of
the same age; while boys tend to display more
actual or threatened hostility to others ("aggressive"). Walker (1962) found similar results
for children of the same age range and in fact
remarks that the difference is as great at 2
years of age as later.
Boys and girls are seen to show different
perceptual responses to Rorschach forms (Ames,
Learned, Metraux, and Walker, 1952). They
have shown, for example, that throughout the
first ten years of life boys give more responses
than do girls in every category. Girls respond
differently to color than do boys, and they
respond more often to the perceived form
alone. The type of response also seems sexdependent. At 31 years of age boys give more
responses than do girls and verbalize more.
Boys see more movement in the figures, and
boys make more mention of urogenital structures. At 7 years of age sex differences in perceptual responses are the most marked. Girls'
responses tend to be neater and more concise.
Boys' records are longer and more involved,
their comments and explanations complicated
and rambling. Girls give more global responses,
boys more details and tiny details. Boys give
more aggressive responses.
Ames and Learned (1954) showed significant
sex differences in developmental trends in block
building and block construction. Like the
Rorschach test, this block-building and construction test supposedly reveals inherent differences
and forms of behavior not significantly influenced by culture. Ames and Learned used
350 children equally divided between the sexes
at ages 2 through 6 years. Conspicuous sex
differences occurred at all ages tested. For example, at 2 years "boys build in a more complex and detailed manner than do girls."
Boys show more responses and show more compact designs. At 4 years, "The structures of
girls fall more than those of boys. Twice as
many boys as girls make one large compact

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ONTOGENY OF HUMAN SEXUAL BEHAVIOR
structure, and many more boys than girls make
scenes." At 6 years: "Nearly twice as many
boys as girls build symmetrically. Many more
boys than girls build one large compact structure. Girls show more interest in size and
color. More girls than boys purposely destroy
their products."
Many more normative studies of similar
character could be presented. In effect, the conclusions and implications of their findings are
summarized by the pediatrician Benjamin
Spock. Spock (1964), in an article entitled "Are
we minimizing differences between the sexes?"
lists sex differences noticeable from birth in
areas of interest, aptitude, and personality, and
concludes: "In terms of basic temperament and
drive there are fairly consistent differences between the sexes, though they may be accentuated or obscured by upbringing." He then
prescribes that for greater security in adult roles
it is better to capitalize on these differences
rather than to minimize them.
The following section presents cases where
these inherent differences were frustrated by
improper assignment of sex role.
Flexibility and sex reassignment
Clinical Evidence. Dicks and Childers (1934)
presented a case of a genetic male child with
hypospadias who from birth to the age of 14 was
treated and dressed in every way as a girl. As
the individual developed, however, he began to
doubt his sex assignment and his interests became "as nearly those of a healthy adolescent
boy as would be possible under the circumstances." Despite the insistence of his parents,
he had no doubt as to his sex and urgently
demanded a transformation to his proper masculine role. After a change was initiated no conflict regarding sexual matters was apparent, and
"his social adjustment was so phenomenal that
at no time was there indicated a need for intensive psychotherapy."
Armstrong (1955) has reported a case of a
male pseudohermaphrodite, a male with undescended testes and hypospadias, who lived as a
girl for 13 years. At the age of 13 years this
condition was revealed, and a plastic repair of
the genitalia was performed. The patient subsequently assumed the male sex very successfully. In reviewing cases of this sort Armstrong
analyzed various problems inherent in this

153

treatment but said, "It should be our duty as
medical practitioners to repair physical abnormality and advise the patient to assume his or
her true sex."
Ghabrial and Girgis (1962) reported two
cases of males who were reared from birth as
females and lived as females until, when old
enough to rebel successfully, declined to continue their malassigned roles. The first individual changed to a male role at the age of 14,
and when seen a year later seemed cheerful,
happy, and apparently well adjusted. The second underwent this change of role at the age of
20, despite a penile amputation at birth (it
being confused for a hypertrophied clitoris).
Notwithstanding the many years and opportunity for gender role learning, rehearsal, and imprinting, both patients insisted on sex reassignment to agree with the sex to which they felt
they belonged.
Norris and Keetel (1962) presented a case of
a female with "a congenital anomaly of the
vagina" who shortly after birth was diagnosed as
having a bifid scrotum with infantile penis. The
child was raised as a male, with corrective surgery to be done at a later date. At puberty the
mistaken diagnosis was revealed and the patient
decided, upon advice from the physicians, to become a female. Plastic repair of the genitalia
was done at age 17. At age 20 a psychiatric
examination revealed "no apparent neurotic
modes of adjustment, no distortion of personality; she related spontaneously and with
warmth.

. .

. a healthy

individual:

no indices

of a neurotic or psychotic mode of adjustment
were elicited." She was then happily married
with a full and complete sexual adjustment. In
regard to general comments in the area of role
assumption, Norris (personal communication)
says:
I feel, as a psychiatrist, that people are amazingly flexible in their ability to handle roles.
This is evident in many other aspects of living. Immigrants come to a new country
where they must speak a new language and
adopt a new social and vocational role, and
most of them adapt to this well. Men are
taught the harm of aggression and taught not
to kill, but during wars are able to adapt to
the concept of doing so after a few months
training, and furthermore, after the war is
over, most return to civilian life with relatively little difficulty, and certainly here are
role changes occurring at a very late age,

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154

THE QUARTERLY REVIEW OF BIOLOGY

which stable people handle without too much
trauma.
I don't believe that sexual role changes
should be any more difficult, assuming an
intact personality.
Dewhurst and Gordon (1963), in an extensive
survey of 18 patients in whom a correction of
malassigned sex role was made after the age of
41 years, contend that 15 of the individuals involved assumed the new role with considerable
success. They correlate this with the inherent
feelings of many of the individuals concerned
that they were being reared in the wrong sex.
These findings are related to the views of Money
and colleagues and are considered as non-supporting and contradictory. Dewhurst and Gordon (1963) write:
. . .several parents, including one couple
who had badly wanted a child of the sex in
which theirs was being reared, believed that
they had observed behaviour more appropriate to the opposite sex. Arguably, if uncertainty had not been expressed, these views
might not have been held, but we are inclined
to reject this, preferring to believe that the
child's natural tendency to the gonadal sex
will sometimes militate against the sex of
rearing and may even overcome it.
The following two clinical reports may be
considered as crucial for the theories involved.
The first case involves a rare patient who, as
an unambiguous male was raised from birth as
a female (Dr. Robert Stoller, personal communication). If gender role is independent of constitutional factors and is dependent only on sex
of rearing and learning, this individual should
have developed psychosexually into a female.
Not only was this not seen, but in this normal
individual rearing seemed to have very little
effect. Stoller writes: "Despite attempts by the
parents to make this child a girl, almost from
birth on the child refused to be comfortable in
the assigned sex or sex of rearing, continuously
fighting all attempts from her feminine mother
to be a feminine daughter. At the age of 14 we
found her to be a genetically and endocrinologically normal male. The patient shifted overnight to a completely normal boy -a most remarkable and successful change." The second
report involves an individual who was raised
as a girl and "appeared to be a girl insofar as
social status and outward sex status was concerned" (Brown and Fryer, 1957). Despite a

female sex assignment without ambivalence and
the body habitus to match, the patient's "normal feelings and reactions" in themselves were
strong enough to prompt a medical consultation concerning the true sexual identity (Brown
and Fryer, 1957, 1964). Clinical examination
confirmed the suspicion of mistaken identity and
"the patient immediately recast his life," and
received corrective surgery. A follow-up study
after 10 years showed the patient happily married and a proud father (Brown and Fryer,
1964).
More cases could be cited. In effect they serve
to demonstrate that inherent male or female
sexual orientation, feelings, and disposition may
develop despite body habitus, sex of assignment,
or rearing. They also indicate that if an incorrect assignment is made, a change in role
may be possible without pertinent psychological
trauma.
It may be noted that most of the cases involved individuals at puberty. This is a time
when inherent diasthetic sexuality, now spurred
by maturation, would indeed be expected to
manifest itself most strongly even if contrary to
a malassigned role. This is what might be predicted from a theory of inherent sexuality, yet
could not be predicted from a theory of sexual
neutrality. It might be asked from what do
these doubts stem, since the family and society
are reacting to the individual as a member of
the assigned sex and it is within that capacity
that reinforcement is found and outside of that
capacity where difficulty would be encountered.
To explain these nontraumatic sex corrections on the basis of a theory of inherent psychosexual predisposition is no problem. The individual is settling into a role for which he or she
is more suited constitutionally, and may even
feel relief in the new role. On the other hand,
to explain not only the origin of doubt as to
proper sex assignment but the ease of sex correction on the basis of a theory of psychosexual
neutrality would necessitate postulating for the
initial gender assignment incomplete imprinting or misprinting, faulty learning, other hypothetical conditions, or a combination of these,
none of which can be adequately substantiated.
This is especially clear in the cases presented,
since it would be difficult to imagine the subsequent imprinting or learning necessary for the

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ONTOGENY OF HUMAN SEXUAL BEHAVIOR
new sex role to be more effective than that for
the initial sex role.
It would be theoretically more parsimonious
to accept the view that inherent in each individual is a diasthetic predisposition to a particular gender role spectrum. If placed in a
situation outside of this particular spectrum,
the individual finds difficulty in adjustment.
Anthropological Considerations. Among societies in which mores permit such changes, an
individual may voluntarily assume a gender role
inconsistent with the one in which he has been
reared and an individual may alter his gender
role well after the so-called "critical period," all
in keeping with accepted modes of their respective societies and thus presumably maintaining
psychological normalcy. Cultures also exist in
which, even though gender roles are not strictly
assigned, the development of sexual behavior
follows a normal nonambivalent course.
These societies may thus provide evidence as
to the relative roles of heredity and environment in sex role status. In societies of the first
type the sex of rearing may exert little evident
effect upon the individual's adult choice of sex
role, and in societies of the second type proper
sexual orientation occurs despite the lack of
strict role assignment. These situations would
seem to indicate an inherent predisposition that
functions despite the presence or absence of
strong environmental ontogenetic influences.
Some of the American Indians provide an
example of a society where sex role changes are
permitted despite strong orientation during rearing (Mead, 1961). Mead says that in tribes where
a berdache [transvestite male] was recognized
as a possible sex career, "male children were
watched and tested from an early age -were
they going to be 'braves' or 'live like women'?
Once the choice was made, elaborate prescriptions of correct social behavior were available"
(emphasis added). The two points to be made
here are the following: (1) that the determiners
of the gender role to be assigned were not based
on morphological sex but on innate and on instinctive self-elaborated behavioral manifestations of the individual; and (2) that, without
trauma to the individual, this role can be assigned and accepted by society postpubertally.
Mead (1961) gives an illustrative example:
"At the time when his bodily candidacy was
remarked there was no living berdache in the

155

tribe, but the women began watching this boy,
and once undressed him to see if he, whose
behavior appeared to them as feminine, 'really
was a male.' Having satisfied themselves as to
his external sex morphology, they then pronounced him to be a berdache. He wore male
exterior clothing but female underwear, was
unmarried

. . ." (emphasis original).

Thus the

berdache is a recognized recurrent sex role that
seems to arise independently in an individual
who possesses unambiguous male genitalia and
is raised in all ways as a male. These individuals, despite their rearing, begin to manifest
feminine behavior patterns and are assigned to
a sex role in accordance with this inconsistency.
Corroborating the assertion that gender role
assignment may be based on an individual's
behavior rather than be a determiner of it are
the various criteria that have been established
among some ethnic groups to aid in determining just such an assignment. Bravery is the
determining masculinizing point among Plains
Indians (males being considered and treated as
females unless brave) (Mead, 1961), and preference for womanly occupations is the female
criterion for males among Samoans (males being
considered and treated as females if they prefer
womanly occupations) (Mead, 1928).
Other anthropological evidence can illustrate
the development of male and female sexual patterns in spite of the lack of specificity in rearing. Data are available for communities where
there is no sex gender in the language and the
names of males and females are undifferentiated
and for communities where juveniles of both
sexes dress alike (Mead, 1961). Societies exist
where boys are classified with women until initiation (Iatmul) and where girls are classed with
men until betrothal (Manus) (Mead, 1961).
Here it would seem that the critical period
would be passed without opportunity for gender
role imprinting and learning! To think or to
expect that these individuals would exhibit no
adult sexual behavioral distinctions or that they
would remain in a sort of sexual limbo is not
in keeping with the facts. It no doubt would
aid in the sexual orientation of individuals
within these cultures if their society had strict
gender taboos and restrictions. But in their
absence, constitutional factors as well as obvious
physical characteristics are sustaining.
Notably, what evolves from anthropological

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156

THE QUARTERLY REVIEW OF BIOLOGY

studies is scattered but abundant evidence that
there occur individuals with the behavior patterns of the opposite sex, in the absence of any
patterned cultural recognition of such a possibility. This conclusion strongly suggests the
presence of some rare but recurring constitutional factor which is less overt than congenital
genital anomalies. It seems safe to assume that
any behavior, sexual or not, which can be institutionalized in a culture and regarded as a recurrent possible human choice has some hereditary,
i.e., genetic, basis (Fletcher, 1957; Mead, 1961).
Fletcher (1957), in defending the role of sexual instincts in man, also calls upon crosscultural data. In concluding this portion of his
discussion he criticizes the attempt to explain all
human behavior in terms of learning cultural
direction and values. His argument is noteworthy:
Two points which have a bearing on the
present question might be mentioned. Firstly,
it seems probable that the tendency to describe individual personalities in terms of
broad cultural uniformities, has gone too far,
and it may be that the whole question of the
degree to which individual persons are 'conditioned' by their 'culture' has been too
readily assumed, rather than demonstrated.
The second point is that the emphasis on
the varieties of behaviour in different human
societies may well have tended to obscure the
similarities; similarities not only of 'instinctexperience' (congenital impulses), but even of
elements of behaviour. Thus, let us consider
behaviour involved in walking, eating, drinking, defecation, sleeping and waking, sexual
intercourse, the care of young infants, fear
and the avoidance of danger. It would seem
that, no matter how varied are the more complicated methods of food-seeking, sanitation,
provision for rest and sleeping, the regulation
of the relations between the sexes, the bringing up of children, the social methods for
avoiding danger, and so on, it remains true
nonetheless, that there are certain basic features of behaviour which are congenital in
man and which are necessarily involved in the
satisfaction of the congenital cravings, some
of which persist throughout his life. Margaret
Mead describes for us three varieties of sexual
behaviour in three societies, but, we suggest,
this merely indicates that the cultural setting
exercises its influence upon the behaviour
adopted in order to satisfy the instinctual demand which is inherited; and the contributors
to the theory of instincts would have no quarrel with this. But if the persisting sexual impulse was not inherited, and if this impulse

did not drive men and women to definite
fundamental forms of behaviour for its gratification, no 'social conditioning' would ever
take place. There would be nothing to 'condition.' No rules regulating sexual relations
would be necessary. There would be nothing
to regulate. If the Cultural Anthropologists
[or any other group] are going to make us
doubt the existence of the sexual instinct in
man (and the same applies to the other instincts) they must show us not how variously
men and women satisfy this instinct in different societies, but a society in which -as
an outcome of the determining influence of
the social environment - there is no evidence
of the sexual impulse, or of the basic forms
of sexual behaviour, at all. We can predict
that such a society is going to be very hard to
find.
Predisposition of Gender Orientation
Genetic Considerations. Primary in any discussion of predisposition towards or away from
a particular pattern of sexual behavior would
be consideration of the possible genetics involved. That animals are subject to inherited
tendencies in relation to their sex roles cannot
be disputed. Young (1957) has reviewed many
of the nonclinical studies and presents evidence
not only showing innate manifestations of sexual behavior patterns but describing how different animal strains can react differently to the
environment. Many recent studies corroborate
these findings (Goy and Jakway, 1959; Jakway,
1959; McGill, 1962a, b; McGill and Blight,
1963a, b). In regard to man, however, our
knowledge is a little more obscure. Kinsey,
Pomeroy, and Martin (1948) state this theme
thus: "The most important biologic factors
affecting the nature and frequency of sexual
response in the human animal are the hereditary
forces which account for the differences between male and female. Within either of these
sexes, heredity must also account for some of
the variation in sensory structures and in the
mechanisms which are concerned with emotional response." However, no other area in
the study of human sexuality seems beset with
as many difficulties as a study of inherited sexuality. Not only would a proper investigation
involve a broad longitudinal survey over many
years but it would have to cover succeeding generations. Nevertheless some data are available.
Kallmann's work (1952a, b) and that of
Schlegel (1962) are probably the most conclu-

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ONTOGENY OF HUMAN SEXUAL BEHAVIOR
sive. Kallmann studied 40 monozygotic and 45
dizygotic twin pairs in which one of the cotwins
was a known overt homosexual. He found 100
per cent of the monozygotic twins concordant
for homosexuality; whereas the dizygotic cotwins were essentially similar to the general
male population. Strikingly, the monozygotic
twins were even comparable in the mode and
extent of their deviance and type of displayed
behavior, and although they had developed their
gender roles independently when separated from
each other. Kallmann considers this evidence,
and I would agree, to throw "considerable doubt
upon the validity of purely psychodynamic
theories of predominantly or exclusively homosexual behavior patterns in adulthood and correspondingly strengthens the hypothesis of a
genically determined disarrangement in the balance between male and female maturational
(hormonal) tendencies" (Kallmann, 1952a).
Schlegel (1962) reviewed reports on 113 twin
couples and found 95 per cent concordant homosexuality in the monozygotic twins and only 5
per cent concordance among the dizygotic twins.
His evidence is in excellent agreement with
Kallmann's data.
Hutchinson (1959), in a broad theoretical discussion on the origins of paraphilia, has reemphasized Kallmann's work and viewed it, along
with animal and other human studies, as leaving little theoretical doubt as to the existence of
a genetic influence on sexual orientations. He
suggests that gene-specific components may affect ". . . the rates of development

of neuro-

psychological mechanisms involved in identification processes....
Recently Melicow and
Uson (1964), in an excellent review of human
sex anomalies, have postulated that there may
exist gene(s) in the sex chromosomes responsible
for "identification and feel of maleness or femaleness." If the normal attachment of this
gene is broken from the Y chromosome in males
or the X chromosome(s) in females, it may
become transposed to another chromosome predisposing to abnormal sex role orientation.
In a most recent work Kallmann (1963) reviews much of the more recent genetic data and
still maintains that genetics are crucially involved in psychosexual development, the mechanism, however, still to be determined.

157

Gedda (1963) has reevaluated Kallman's data
statistically and claims to have computed that
they show a minimum genetic contribution of
30 per cent in the etiology of homosexuality.
Hampson and Hampson (1961) and J. L.
Hampson (1964) have considered Kallmann's
work, but regard his evidence as being outweighed by two types of studies. The first of
these is exemplified by the work of Pare (1956),
who, using the Barr technique for sex chromatin
analysis, investigated male homosexuals for presence of the female chromatin body in the cell
nucleus. Pare found no difference between the
sex chromatin of the homosexuals and control
males. This is a weak counter argument to the
genetic one, since a negative finding of this sort
is not necessarily evidence against the importance of genetic differences. With present techniques, chromosomal studies can do little more
than indicate the presence of an extra sex chromosome or deficiency of an entire sex chromosome, or a gross translocation. They cannot
reveal a single deviant gene or even several. The
second type of study is more weighty, and consists of psychiatric and psychological reports
which claim psychosexual disorders to be the
result of social learning. These are exemplified
by the reports of a multitude of workers who
describe family situations and experiences which
supposedly provide a basis for homosexuality.
Green and Money (1961a, b) also attribute sexual deviation to certain kinds of experiences.
In discussing the possible etiology of effeminacy
in 5 prepubertal boys they cursorily review and
dismiss the possible influence of a genetic involvement and prefer instead to consider only
improper imprint experiences at an early age,
despite the fact that common imprint experiences could not be proved. Gildea and Robins
(1963) commented on the comparative findings
of Kallmann and of Money in the following
terms:
His [Kallmann's] findings of perfect concordance for homosexuality in identical twins
would indicate that homosexuality is in some
way genetically determined and that the process of rearing cannot override the genetic
constitution. Kallmann's findings do not fit
very well with Money's emphasis on the crucial importance of rearing in determining
sexual direction.

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158

THE QUARTERLY REVIEW OF BIOLOGY

Dobzhansky (1962) too comments on social experience, genetics, and human sexuality, thus:
"Let us suppose that all persons who exhibit
deviant sexual behavior as adults are found to
have had certain kinds of experience in their
childhood, particularly in their relation to their
parents. But does it follow that such experiences induce sexual deviations in everybody who
had them in his biography? Or does this happen only to the carriers of certain genetic endowments, which are apparently not rare in
human populations?" Undoubtedly we are
dealing with an interaction of genetics and experience; the relative contribution of each,
however, may vary with the particular behavior
pattern and individual concerned. Effeminacy
and other sexual deviations are not altogether
rare in our society. Without contending that
inheritance is the whole cause, we may well consider it influential and predisposing. A quotation from Mead is again applicable: "It seems
safe to assume that any behavior which can be
institutionalized in a culture and regarded as
a recurrent possible human choice has some
hereditary base" (Mead, 1961). This hereditary
base is what, especially for other animals, is
usually termed an innate and instinctual framework within which the individual develops,
meets, and contends with his environment.
Most individuals, falling within the range of
normal sexual behavior for our society, may be
considered as following a path of genetic least
resistance - that of their "innate instincts." In
analyzing human behavior, trying to separate
genetics and experience may be like trying to
separate hydrogen and oxygen in their importance with respect to the properties of water.
Those misassigned individuals who go against
the predisposition inherent in their genetic
make-up overcome it only to the extent their
genetic flexibility will allow.
Schultz (1963), in reviewing psychosexual
problems associated with intersexuality and
transvestism, stated in regard to the origin of
psychosexual orientation that:
The ultimate basis of hereditary endowment is influenced peristatically from the
earliest time onward by the action of hormones which again are perhaps accessible not
only to broadly somatic but even neuropsychiatric influences. Thus the love-life is fitted
biologically to the dynamic totality of the
constitutional make-up, and this unitary

formation corresponds in psychic range to
the not less dynamic personality development. Even this rests on primary assumptions
of a genotypic and certainly mainly primitive kind, of which the development, now
thoroughly analogous to the development of
constitution, is determined by an immense
number of conditions.
In the development of any behavior pattern
we must consider not only the stimuli serving
to mold the pattern but the nature of the receptive medium which is to be molded. Many humans, sibs in particular, can be subjected to
extremely diverse experiences and still develop
similar personalities; conversely, humans may
be subjected to like experiences and develop
quite differently. The individual's constitutional capacity to respond to these environmental stimuli exerts its influence, too. It is the
genetic heritage of an individual which predisposes him to react in a particular manner so
that the learning of a gender role can occur.
Even if one thinks in terms of imprinting and
innate releasing mechanisms (IRM) (Money,
Hampson, and Hampson, 1957; Money, 1960a),
these concepts must be recognized as implying
that the individual possesses a genetic heritage.
The IRM does not appear de novo but is
species-specific and, as its name says, innate.
Hormonal Organization of Sexual Behavior.
To support the theory of psychosexual neutrality at birth we have been presented with no
instance of a normal individual appearing as an
unequivocal male and being reared successfully
as a female, or vice versa. Wherever the etiology
of the hermaphroditism was determined the particular patients had been subjected, during their
prenatal or neonatal existence, to a genetic or
hormonal imbalance, or both (Hampson and
Hampson, 1961). This imbalance may provide
the requisite basis for what seems to be psychosexual neutrality. Schultz considers that in
normal individuals there are in the two sexes
differential psychosexual tendencies which determine the degree of male or female characteristics each individual will manifest. Hermaphrodites, however, he considers to possess an "undifferentiated constitution," since they display
a sexual erotic state low in vigor, and occasionally bordering on the eunuchoid, yet with
nothing specific in incidence or character
(Schultz, 1963). Benjamin (1964) reports that

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ONTOGENY OF HU1MAN SEXUAL BEHAVIOR
for transsexual individuals, "A certain significance endocrinologically may be attached to the
fact that in 28 out of these 91 patients, a more
or less distinct immaturity and hypogonadism to
the point of eunuchoidism was found."
striking disturbance of
["Transsexualism-a
gender role and gender orientation. It is a disorder of the harmony and uniformity of the
psychosexual personality" (Benjamin, 1964).]
It has long been recognized that various hormones are potent regulators of human behavior.
Earlier cultures had a knowledge of the effects
of castration, and much recent evidence is available to confirm the role that androgens serve in
sexual drive and activity in men.
Occasional studies to the contrary, the bulk
of evidence indicates that testicular androgens
activate libido, and that castration or other
androgen loss due to some pathological condition reduces libido. Reviews (Lipschiitz, 1924;
Tauber, 1940; Beach, 1948a, b; Kinsey, Pomeroy, and Martin, 1948) and more recent case
studies (Bremer, 1959) can readily document this
conclusion. Bremer (1959), in evaluating the
effect of castration in 157 cases, says:
. . . in all cases without exception the amount
of sexual activity has been altered. It has
been reduced or abolished, irrespective of the
direction or the form of sexual urge - heterosexuality, homosexuality, fetichism, zoophilic
actions, masturbation, exhibitionism, or fetichistic actions . . . [emphasis original].

Females too are influenced by their endocrines.
The early work of Foss (1937), Shorr, Papanicolaou, and Stimmel (1938), Loeser (1940), Geist
(1941), Salmon and Geist (1943), Kupperman
and Studdiford (1953), and the recent work from
the Sloan-Kettering Institute is probably quite
definitive in this respect (Waxenberg, Drellich,
and Sutherland, 1959; Schon and Sutherland,
1960; Sopchak and Sutherland, 1960; Waxenberg, Finkbeiner, Drellich, and Sutherland,
1960; Waxenberg, 1963). These studies show the
significant role androgens usually play in contrast to the "female" hormones, the estrogens
and progesterone, in maintaining and stimulating erotic inclination, sexual desire, and behavior in females. In males the origin of the
androgen is primarily from the testes, in the
female from the adrenal and the ovary itself.
The androgenic influences are acknowledged

159

by Money (1961a). However, he sees them as
supporting the neutrality theory, essentially on
the following line of reasoning. Sexual desire
and erotic functioning of both men and women
are dependent upon a similar group of substances - androgens. Since men react to androgens with male sexual behavior and females
react to androgens with female sexual behavior,
the hormones are nondirectional, only activational, and the direction comes from another
source. "The direction or content of erotic inclination in the human species is not controlled
by the sex hormones. Hormonally speaking, the
sex drive is neither male nor female but undifferentiated - an urge for the warmth and sensation of close body contact and genital proximity" (Money, 1961a). The direction taken by
the drive is assumed to be learned or imprinted
purely from the sex of rearing. Hampson and
Hampson (1961) have stated that among patients whose sex hormones and secondary sexual
body development contradicted the sex of rearing only 16 per cent were unable to adjust unambivalently to the assigned sexual role. Thus
they reason that sex hormones do not act as
causal agents in the establishment of an individual's gender role and psychosexual orientation.
Perloff (1949, 1963), Kinsey and his associates
(1948, 1953), and others also suggest that in the
adult human individual endocrines are not the
sole instigator or sole director (or both) of sexual
behavior. Indeed, this position is not under contention. But to say that something is not the
cause or sole director of a particular effect does
not mean that it has little or no influence. Admittedly, hormones are probably not the single
causal agent that induces gender role orientation, but their influence is undeniable and
strong. Money (1961e) has said, "The sex hormones, it appears, have no direct effect on the
direction or content of erotic inclination in the
human species. These are assumed to be experientially determined." But the importance of
the hormones in this regard was implicitly admitted, since hormonal therapy was recommended for correction of psychosexual and
physical doubt (Hampson and Hampson, 1961).
George W. Corner in his classic book The Hormones in Human Reproduction (1942) has said:
Human [sexual] behavior involves all sorts
of mental processes not subject to experi-

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160

THE QUARTERLY REVIEW OF BIOLOGY

mental control. We may be sure, however,
that the hormones have an important part in
the matter, directly or indirectly, and that
without them there could be no human mating.

These hormones, however, can affect behavior
only to an extent that is inherent and previously organized within the soma. Boss (1943), in
considering the activating properties of hormones in regard to a somatic base of sexual behavior, stressed that genetic factors are strongly
involved, not only in determining the specific
pattern of the taxonomic unit, but also of the
sex. She considered this to be demonstrated by
the widely if not generally valid rule that the
same amounts of hormone do not produce identical reactions in the two sexes of a given species.
Young (1961) has expressed a similar idea as
follows: "We feel that the responses that the
members of different sexes give to hormonal
stimulation are predetermined; in this sense a
specific rather than a non-specific relationship
exists." Harris (1964) most recently presented
the idea in this manner: "This [sex specific
differential behavior response to hormones] reflects, in all probability, some anatomical or
biochemical difference in the central nervous
system of the two sexes."
A most critical point to be elaborated here
is that although endocrines may be primarily
activational in the adult, in the fetus or neonate
they must be considered directional. Phoenix,
Goy, Gerall, and Young (1959) have clearly
demonstrated that female guinea pigs are behaviorally as well as somatically masculinized by
an androgen, testosterone propionate, prenatally
injected into the mother. Postnatal behavior,
more than the genitalia, was shown to be liable
to alteration by the androgen, as even somatically unaffected females were behaviorally masculinized. Genetic females, if potentiated by
androgens, manifested a suppression of the capacity to display lordosis following estrogen and
progesterone treatment, and male-like mounting
behavior was displayed by many of these animals even when lordosis could not be elicited
(Phoenix, Goy, Gerall, and Young, 1959). Similar studies with the rhesus monkey afforded comparable results, that is, prenatally administered
androgens will alter the normal female behavior
patterns and genital structures to those of the
male (Young, Goy, and Phoenix, 1964). These

data may be taken as evidence of the organizing
ability of prenatally acting androgens on the
neural tissues mediating sexual behavior. Human females, in utero, also have been shown to
be structurally modified by androgens (Wilkins,
Jones, Holman, and Stempfel, 1958; Grumbach, Ducharme, and Moloshok, 1959; Grumbach and Ducharme, 1960; Diamond and Young,
1963). Although it has yet to be adequately
demonstrated that these embryonic individuals
were behaviorally affected, the possibility is
within reason and not without zoological precedent. A possible mechanism for genes and hormones to interact and provide direction has
recently been suggested. In contrast to the wellknown evidences that genes can control hormonal activities, Karlson (1963) proposes and
cites experimental evidence to show that steroid
hormones are capable of altering and controlling gene activity. If such an alteration were to
occur in cells within the (behavior mediating)
nervous system we might expect an influence
on subsequent behavior, certainly if the change
were to occur during a critical prenatal period.
Just as the presence of androgen has been
demonstrated to be crucial, the prenatal absence
of androgens is also crucial for the organization
of mammalian tissues.
Although it has not yet been definitely shown
that the morphogenic substance elaborated from
the fetal testis is an androgensimilar in character
to adult testoids, most inferential evidence points
in this direction (Burns, 1961).
Jost (1958) and Burns (1961), in excellent reviews, have cited the experimental evidence
indicating that sexual differentiation of the
normal male and female is dependent upon the
presence of testicular substances. If testicular
substances are present the differentiation is
masculine; if absent, the differentiation is feminine. Males castrated prior to sexual differentiation develop structurally as females; in them
there is an absence of external male genitalia
and maintenance of derivatives of the Miillerian
duct, e.g., the fallopian tubes, uterus, etc. Comparable human evidence is available from different types of hermaphroditic individuals;
those with gonadal (testicular) aplasia (Grumbach, Van Wyk, and Wilkins, 1955; Grumbach
and Barr, 1958; Jones and Scott, 1958; Wilkins,
1960; Overzier, 1963; Armstrong, 1964) and tes-

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ONTOGENY OF HUMAN SEXUAL BEHAVIOR
ticular feminization (Morris, 1953; Grumbach
and Barr, 1958; Jones and Scott, 1958; Marshall
and Harder, 1958; Barno, 1962; Kendall and
Loewenberg, 1962; Morris and Mahesh, 1963;
Overzier, 1963; Armstrong, 1964) in particular.
These genetic males are phenotypically female.
Hampson, Hampson, and Money (1955) have
claimed that since these individuals who possess
a male chromatin pattern, can assume a gender
role as normal females it means that the gender
role is assumed independently of the genetic
sex. It must be recognized that these genetic
anomalies deprive the developing fetus of
proper gonadal substances which in the human
species, as demonstrably in other animals, may
potentiate and organize the nervous system for
masculine behavior. The deprivation of typical
hormones or the presence of heterotypical ones
may simultaneously potentiate and organize the
nervous system for female behavior.
Most significant are the findings which bridge
the hormonal induction phenomenon discussed
above and the resulting demonstrable sex-specific differences in the nervous system, in the
hypothalamus in particular. Harris and Jacobsohn (1950, 1951), Martinez and Bittner (1956),
Harris (1964), and Gorski and Wagner (1965)
have shown that early in development the hypothalamus is differentiated into a male or female
type. Their studies emphasize this in regard to
the hypothalamo-hypophyseal axis in particular.
Pituitaries transplanted beneath the hypothalamus from males or females into hypophysectomized castrated males will not cycle, whereas
hypophysectomized females bearing either male
or female pituitary grafts show complete and
normal estrus cycles.
Later Barraclough (1961), Barraclough and
Gorski (1961, 1962), Harris and Levine (1962),
Whalen and Nadler (1963), and Gorski and
Barraclough (1963) demonstrated how this sexual differentiation of the hypothalamus may be
achieved relatively simply with a single injection of steroid in a neonatal animal whose
nervous system is still undifferentiated sexually.
These experiments reflect on the organization
of neural tissues implied in the work of Phoenix,
Goy, Gerall, and Young (1959) and most probably occur in nature by means of the induction
of gonadal substances.
The implications are clear. The well-known

161

and documented instances of hormonal regulation of sexual behavior below the human level
are seen to be brought under neural mediation.
With a broader outlook we see that genetic
forces induce gonadal development, and gonadal
development is normally followed by the elaboration of fetal or neonate gonadal substances
responsible for the sexual differentiation of the
nervous system. The neuroendocrine relations
of the hypothalamus are the most obvious entities affected but it may be surmised that other,
purely neural, aspects are also differentiated or
potentiated at this time.
Since most sexual anomalies are under genic
control (Grumbach and Barr, 1958; Jones and
Scott, 1958; Overzier, 1963; Armstrong, 1964;
Beatty, 1964; Brunner-Lorand, 1964), it may be
inferred that it is via such indirect and subtle
means, as through hormonal action, that genes
may be expected to influence organization of
the nervous system and to mold sexual behavior. Thus rearing and assignment based on
phenotype are not all that is involved in analyzing the etiology of sexual behavior in hermaphrodites. Those individuals with a male
chromatin pattern who successfully assume a
female gender role do so with the absence of
crucial (hormonal) potentiating factors that
may, in a normal male, establish a male constitution and a predisposition for the assumption
of a male gender role.
In the only behavioral studies of their kind to
date, Grady and Phoenix (1963), and Feder and
Whalen (1965), working with William C. Young,
have completed studies which show that male
sexual behavior is influenced by the loss of
the neonatal gonad. They castrated male rats
prior to sexual differentiation and observed that
when reaching the normal age of maturity these
rats fail to show inasculine behavior and can
readily be induced to show female behavior.
Phoenix, Goy, Gerall, and Young (1959) aptly
summarize these sorts of data:
For the neural tissues mediating behavior,
corresponding relationships [to the development of the genital tracts] seem to exist. The
embryonic and fetal periods are periods of
organization or "differentiation" in the direction of masculinization or feminization. Adulthood, when gonadal hormones are being
secreted, is a period of activation; neural tissues are the target organs and mating behavior is brought to expression. Like the genital

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162

THE QUARTERLY REVIEW OF BIOLOGY

tracts, the neural tissues mediating mating
behavior respond to androgens or to estrogens depending on the sex of the individual,
but again the specificity is not complete
(Antliff and Young, 1956; Young, 1961).
They go on to discuss the question of inherent
neural bisexuality as follows:
Like Dantchakoff (1938a, b, c), Raynaud
(1938), and many others (Beach, 1945a; Steinach, 1913, 1916; Lipschiitz, 1924; Beach, 1942,
1945b), the existence of a bisexuality is assumed. We suggest, however, that in the adult
this bisexuality is unequal in the neural tissues as it is in the case of the genital tissues.
The capacity exists for giving behavioral responses of the opposite sex, but it is variable
and, in most mammals that have been studied
and in many lower vertebrates as well, it is
elicited only with difficulty (Young, 1961).
Therefore, when we consider prenatal as well
as postnatal existence, hormones may be regarded as directional as well as activational; and
at birth the individual may be considered to
have been neurally predisposed by genetic and
hormonal means toward one sex. Since this
predisposition is demonstrated so vividly in animals, including anthropoids, we may logically
assume that it persists in the human after birth,
although manifestations of it may be suppressed
or modified. In a recent review article Young,
Goy, and Phoenix 1964) expressed such confidence about this point that in relation to the
theory of Hampson and Money they stated:
"In view of what we have learned an endocrinological basis which is consistent with the
concept of psychologic bisexuality exists for the
interpretation of most if not all of the cases
they report."
The Nervous System. In discussing behavior,
we find it inevitable to consider in some detail
its medium - the nervous system. The point at
issue here is whether the nervous system is just
a neutral responsive system intermediate between stimulus and response, or is a system with
a built-in diasthetic bias. This consideration is
crucial, since it is on the nervous system that
potentiation and organization must exert their
influence and it is on the nervous system that
learning (to be discussed below) exerts its effect.
Previously, genetic and hormonal factors were
seen to be capable of organizing the nervous
system to direct future sexual behavior. More
direct, immediate, and independent influences

of the nervous system may be understood from
clinical studies and from experiments investigating behavior by means of ablation, lesion
placement, direct stimulation, direct application
of hormones, electrical self-stimulation, or electrical recording. These various methods reveal
different functional levels of activity and the
sites of so-called "sex-centers"- loci for the
integration of the component activities of a
particular sex behavior pattern. Significantly,
these studies often reveal inherent differences
of the nervous system dependent upon gender.
Were a "neutral" nervous system to exist, identical effects would be expected from individuals
of both sexes.
The majority of direct studies do not set out
primarily to investigate response differences between the sexes. These differences are in fact
taken for granted, and sex-specific response patterns such as lordosis and estrus behavior are
used as dependent variables. The functional
role of a specific locus or structure is thus usually analyzed only in relation to the anticipated
patterns applicable to the sex of the animal
investigated. But although male-female comparisons are not usually made, direct studies
are of value in illustrating that loci within the
nervous system possess inherent properties related to sexual disposition, behavior, and manifestations of gender role.
The most significant differentiation of the
hypothalamus has been mentioned above in
discussing the role of the endocrines in sexual
differentiation. The hypothalamus has for quite
some time been implicated both indirectly and
directly in influencing sexual behavior patterns. Its indirect functioning via the hypophysis has been discussed by Harris (1955, 1956,
1960, 1964), Green (1956), Greer (1957), Sawyer
(1960, 1962), Szentagothai, Flerko, Mess, and
Halasz (1962), Nalbandov (1963), Everett (1964),
and others. The significance of this functional
pattern was discussed in an earlier section
(p. 161). Direct functioning without hypophyseal involvement has been suggested by the experiments of Brookhart and Dey (1941), Clegg,
Santolucito, Smith, and Ganong (1958), Sawyer
and Robison (1956), Robison and Sawyer (1957),
Soulairac (1959), Soulairac and Soulairac (1956),
Phoenix (1961), and Goy and Phoenix (1963).
These studies inferring direct hypothalamic

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ONTOGENY OF HUMAN SEXUAL BEHAVIOR
involvement indicate a sex-specific functioning
of certain loci. Crucial for our argument are
instances where similar loci were investigated in
both males and females. For example, Goy and
Phoenix (1963) have demonstrated that midventral hypothalamic lesions in female guinea
pigs result in an alteration of the normal sexual
behavior ranging from a complete loss of the
capacity to display estrus to permanent estrus,
depending upon the precise locus of the lesion.
In male guinea pigs (Phoenix, 1961) similar lesions also produced behavioral alterations. The
type of alteration is significant. Lordosis was
lost in the female, and mounting was lost in the
male.
Many reviews (Beach, 1951; Goldstein, 1957;
Sawyer, 1960, 1962) detail the relative dependence of the male and independence of the female on the cortical mass in relation to the
competent expression of sexual behavior. Complete removal of the cortex will not prevent
mating responses in the female rat, cat, rabbit,
or guinea pig, whereas destruction or removal
of 75 per cent of the male cortex completely
abolishes the male mating pattern. In female
rats which spontaneously exhibit male-like
mounting, decortication stops this behavior
whereas the usual female behavior components
are unimpaired (Beach, 1943). While it may
be argued that most of the data are from nonhumans, Ford and Beach (1951) have suggested
that the human male and female are also differentially dependent upon cortical mass relative to their expression of sexuality. These,
then, are indices of sexually differentiated nervous tissues.
The classical work of Kliiver and Bucy in
1939 and by Kliuver (1952) afterwards showed
that sexually mature male macaques respond to
bilateral removal of the temporal lobe by hypersexual activity: heterosexual, homosexual, and
autosexual in direction. The female does not
show this. Significantly, however, Kluver (1952)
remarked, ". . . an intensification

of sexual re-

sponses may occur even in a pseudohermaphrodite or in a female from which the uterus and
both ovaries have been removed prior to extirpating the temporal lobes." Later in his review
Kluver (1952) added, "There is no doubt that
age, sex, species and many other factors influence the picture of behavior alterations pro-

163

duced by a bilateral temporal lobectomy."
Schreiner and Kling (1953, 1954, 1956) and
Green, Clemente, and De Groot (1957) have
similarly demonstrated that lesions in the piriform cortex of the male cat induced hypersexual
changes, whereas hypersexuality was not usually observed in female cats with similar lesions.
Analogous functioning of the human cerebrum
may be inferred from clinical reports of the
Kliuver-Bucy syndrome (Sawa, Ueki, Arita, and
Harada, 1954; Terzian and Dalle Ore, 1955) and
other disorders of the temporal lobe (Epstein,
1960, 1961). Interestingly, these reports show
sexual deviation manifested only in men.
Lansdell has reported a sex difference in
verbal ability (1961) and in design preference
(1962), which reacts differentially to temporal
lobe surgery. After surgery to the dominant
lobe, women maintain their previous "artistic
judgment" while men lose theirs. "The effects
of the operations suggest that some physiological
mechanisms underlying artistic judgment and
verbal ability may overlap in the female brain,
but are in opposite hemispheres in the male"
(Lansdell, 1962).
On a more subtle level, perceptual differences
between males and females can be considered.
In children, the work mentioned earlier with
Rorschach tests (Ames, Learned, Metraux, and
Walker, 1952) and block building (Ames and
Learned, 1954) is suggestive of the presence
within the nervous system of perceptual and
cognitive processes which are early manifested
sex differences. On a purely neurophysiological
basis Lipsitt and Levy (1959) have shown that
as early as the first three days of life females
show a lower threshold to electric shock stimulation than do males.
Adult women usually have greater olfactory
acuity than men (Schneider and Wolf, 1955)
and this has been seen to vary with hormone
levels (Schneider, Costiloe, Howard, and Wolf,
1958). Kinsey et al. (1953) reported that males,
more often than females, are erotically oriented
to visual cues. Females may be more susceptible
to tactile stimuli. Sexual distinctions such as
these cannot help but influence various aspects
of an individual's life, including the way he or
she views and reacts to the world, and hence
gender role.
It may be argued, as Money (1963a) does, that

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THE QUARTERLY REVIEW OF BIOLOGY

164

differences such as perceptual responses are results of learning rather than inherent in the
nervous system and causal. However, Money
presents no model to explain how or why perceptual thresholds to stimuli which are obscure
and novel, such as those used by Lansdell, may
be differentially altered and learned, particularly where the patient is unaware of a desirable
direction for the change. Because of the nature
of the tests and the early ages at which they
were administered, it would also be difficult to
explain how the Rorschach and block-building
tests were biased by learning.
It may be concluded that the nervous systems
of males and females are differentially reactive
to the environment. And there is good reason
to believe that these differences, so definite in
humans as well as in other animals, are present
and influential at birth and afterwards.
Imprinting. Hampson and Hampson (1961)
contend that:
The premise that behavior is based primarily on instincts is gradually disappearing
from scientific writing and the traditional
concept of instinct is undergoing revision and
modification. In its place has emerged the
view that early experience importantly structures subsequent behavior. This is not to
say, lest misunderstanding arise, that the animal

organism

-

human

or

subhuman

-

is

merely a blank slate to be written upon by
the capricious finger of life experiences. Quite
the contrary, for there are now many studies
in the literature dealing with genetic constitution and the inheritance of basic capacities
affecting later learning, temperament and
personality.
This theme is developed so that the constitutional factors are considered insignificant when
compared with ontogenetic factors. Difficulty in
incongruous sex orientation or modification of
sex is thought of in ontogenetic terms of crucial
timing and imprinting.
To support their view, Beach and Jaynes
(1954) were cited by Hampson and Hampson
(1961) to show how early experiences may
modify behavior. Emphasis was placed on the
last of three possibilities given by Beach and
Jaynes, namely, that which postulated a "critical
period" in ontogeny during which certain types
of behavior are irrevocably structured for the
remainder of the organism's life. However, once
stated, the possibility was accepted as an estab-

lished fact. Hampson and Hampson allow, it
is true, for species variation, but now consider
this variation to be minor.
Neither the Hampsons nor Money give criteria
to indicate when they think species differences
(between humans and other animals) are negligible. They are grossly inconsistent in this respect.
In relation to basic sexual tendencies, the human
is assumed to be quite distant even from o,ther
mammals. But in relation to imprinting, seen
definitely only in birds, men and birds are assumed to be quite close.

Hampson and Hampson have not recognized
that Beach and Jaynes mentioned, in the same
paragraph, when referring to critical periods
and imprinting in humans and birds: "It is
tempting to suggest the existence of similarities
in underlying mechanisms, but this would be
unwarranted on the basis of present knowledge"
(Beach and Jaynes, 1954). Schiller (1957) in
Instinctive Behavior, isolated imprinting as predominantly avian and contrary to mammalian
behavior. Fletcher (1957), in his book Instinct
In Man, although discussing human sexuality
at length, did not even consider the possibility
that imprinting might be involved in the behavior of humans. Nevertheless, the "psychosexual neutrality-at-birth theory" assumes the
human species, in regard to the establishment
of gender role, to be analogously imprinted
(Money, Hampson, and Hampson, 1957; Money,
1960a, 1961b, d; Hampson and Hampson, 1961).
Money has even gone so far as to say, "It is
quite likely that aberrations of sexual inclination and behavior, the so-called perversions, are
errors of imprinting," and that "the phenomenon of falling in love can be analyzed as an
imprinting phenomenon" (Money, 1960a).
Since no experimental studies on the imprinting of human sexuality per se are available,
animal experiments may provide further insight
into such a possibility. Young (1961), in reviewing isolation experiments with the guinea
pig, stated, "The data as a whole indicate that
the emergence of sexual behavior patterns in
the male guinea pig is not restricted to an early
critical period comparable with that described in
the literature dealing with imprinting (Lorenz,
1937)." Rats, too, have been shown to be relatively free from the need of sexual imprinting

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ONTOGENY OF HUMAN SEXUAL BEHAVIOR
(Beach, 1958), and so have mice (King, 1957).
Since lower mammalian species are free of an
imprinting requirement for competent sexual
behavior, it seems that it would be difficult to
defend the proposition that humans, a behaviorally more flexible species, are subject to such
an imprinting stereotype.
Admittedly, although many species and individual variations exist (Scott, 1962), "critical periods" do exist for mammals in regard to reproductive phenomena. But while reproduction
may be affected, assumption of a sexual role may
not be. A normal rhesus monkey raised in isolation may not react sexually sufficiently to mate,
but a male still follows male behavior patterns
(albeit deviantly); and a female, female patterns. Harlow (1961) has mentioned that many
types of sexually dimorphic behavior patterns
such as play, aggression, and receptivity, which
are as much a part of the proper gender role as
coitus, arise spontaneously in isolated male and
female monkeys. He said, "It is unreasonable to
account for these sex differences as learned, culturally ordered patterns of behavior because
there is no opportunity for acquiring a cultural
heritage, let alone a sexually differentiated one,
from an inanimate cloth surrogate" (Harlow,
1961). This conclusion is in contradistinction to
the response of the female rhesus which, as mentioned earlier, when potentiated by prenatal
androgen injections, behaves not as a deviant
female but as a male. There seems to be little
doubt that normal humans would manifest sexually dimorphic behavior patterns even if raised
in isolation.

It is interesting here to consider the following
point. If imprinting were involved to any great
extent and the gender role independent of a
more significant sexual instinct, then a neutrality theory would have to contend with the
fact that for the first three years of life babies
are almost exclusively with their mothers (or
some other female), and yet male children are
usually not imprinted as females. This fact must
be considered in the light of the observations
that imprinting, as we see it in birds, occurs
within the brief space of a few hours and irrespective of sex. Nothing really comparable to
imprinting has been demonstrated to occur in
human sexuality.

165

Learning and Reinforcement
The concept of reinforcement is important and
basic to any learning theory. A reinforcement is
any change in the organism or in the environment
which has the ability to increase the probability
of occurrence of some particular behavior performed just prior to the presentation of the reinforcement (Thorndike, 1913; Hull, 1952). Thus,
orgasm may be reinforcing to an animal and
increase the probability of some action required
to obtain the orgasm.

Much of the psychosexual "neutrality at
birth" theory depends upon the great part that
learning plays in the instillation of masculine
and feminine gender roles (Hampson and
Hampson, 1961; Money, 1960a, 1961e). Sears,
Maccoby, and Levin (1957), Rabban (1950), and
others are cited by Hampson and Hampson
(1961) as indicating that culture and learning
shape subsequent behavior. Ehrmann (1963) has
recently provided an excellent review of various
studies investigating the social determinants of
human sexual behavior. These studies indeed
indicate that gender personality is influenced by
society and thus, in part, is learned. But Ehrmann wisely started his review by emphasizing
that in looking for the social determinants of
sexual behavior one must take into account biological considerations and not simply learning
processes. Benjamin (1964) in a very recent
study of transsexual individuals could find no
evidence that childhood conditioning is involved
in the etiology of the transsexualism in 47 out
of 87 patients. Of the remaining 40 patients
conditioning was of "doubtful" influence in 24
individuals and definitely influential in only
16 cases.
As a function of learning, assumption of a
gender role presumably should follow the characteristics of a normal learning curve. But, when
viewed properly, modifiability of sex behavior
by learning must be seen also as a disproof of
the imprinting theory, for the same modifications of behavior cannot be caused both by
learning and by imprinting in the same species.
The basic incompatibilities are that learning
requires reinforcement while imprinting does
not, and that imprinting is fixed and irreversible
while learning is not. But even to grant that
assumption of a gender role by an individual in
our society may be molded by learning in no

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166

THE QUARTERLY REVIEW OF BIOLOGY

way proves that it is the sole or dominant determiner of the gender role. Money, Hampson,
and Hampson would have us believe so. Hampson and Hampson (1961) contend:
In the human psychological sexuality is not
differentiated when the child is born. Rather,
psychological sex becomes differentiated during the course of the many experiences of
growing up, including those experiences dictated by his or her own bodily equipment.
Thus, in the place of the theory of an innate,
constitutional psychological bisexuality such
as that proposed by Freud - a concept already questioned on theoretical grounds by
must subRado (1940), among others -we
stitute a concept of psychologic sexual neutrality in humans at birth. Such psychosexual
neutrality permits the development and perpetuation of divers patterns of psychosexual
orientation and functioning in accordance
with the life experiences each individual may
encounter and transact.
Rado (1940) indeed questions the concept of
bisexuality, but nowhere does he assume neutrality at birth. Instead, he claims that there is
at birth a differentiated unisexuality. He states,
"Under normal developmental conditions, as differentiationproceedsand one type of reproductive
action system grows to completion, the original
bipotentiality ceases to have any real significance....

The standard developmental pattern

of our species provides for each individual only
one reproductiveaction system. The two inherent
potentialities of the zygote are thereby mutually
exclusive."
It is not obvious, when we examine the best
possible evidence, how the criteria of learning
can be logically applied to the hermaphroditic
evidence. Yet to do just that is the core of their
philosophy, which asserts that if gender roles
are modified by learning or are established by
imprinting, then sexual behavior patterns are
not prenatally mediated. Here is a subtle non
sequitur. All evinced learning, be it operant or
classical, is by definition a modification of behavior (Verplanck, 1957). The evidence presented in this paper indicates that the learning
of a gender role is a culturally fostered ontogenetic phenomenon of development superimposed on a prenatally determined pattern and
mechanism of sexual behavior. As Tinbergen
(1951) has stated, "There is a close relationship
between innate equipment and learning processes, in that learning is often predetermined by

the innate constitution. Many animals inherit
predispositions to learn special things, and these
dispositions to learn therefore belong to the
innate equipment." This predisposition may be
considered also in terms of differential endocrine
sensitivity. The nervous systems of males and
females subjected to genetic and hormonal factors may present an altered learning capability
that sets limits to or extends the range of sexual
behavior possible to the individual. Hutchinson
(1959) has proposed that the individual's genetic
endowment operates to mold behavior by affecting "the rates and extent of development of the
neuropsychological mechanisms underlying the
identification process and other aspects of object
relationships in infancy." An extensive search
of the literature reveals no case where a male
or female without some sort of biological abnormality, e.g. chromosomal, hormonal, or gonadal, accepted an imposed gender role opposite
to that of his or her phenotype. If such an individual is available he has not been referred to
by proponents of a "neutrality at birth" theory.
It may be assumed that such an individual will
be hard to find, since this anomalous behavior
would be outside normal limits.
Human hermaphrodites, it would seem reasonable to assume, are somehow altered in their
neurophysiological capacity towards or away
from certain features of sexual behavior. But
since their behavior still falls within the broad
scope of normal behavior their actions usually
go unchallenged. It might also be pertinent
here to state that, in humans, behavior can be
affected and that for females passivity may serve
as "normal" sexual behavior and thus seriously
hamper any rating system of "femaleness." An
individual's personal conviction as to his or her
sex, even if bolstered by suitable genitalia, may
lack the essential reinforcing properties of orgasm. For females this normally does not seem
to be crucial (Wallin and Clark, 1963), but for
males orgasm may be a necessary reinforcement
of the sex role (Ford and Beach, 1951). This
greater dependence of males upon orgasm as
reinforcement may be significant in a more general way, in that males are more capable of sexual learning and conditioning, whereas females
seem to show a relative absence of such processes (Ford and Beach, 1951). Parenthetically,
we may mention the existence of differences

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ONTOGENY OF HUMAN SEXUAL BEHAVIOR
in genital response, only recently investigated.
These could hardly have been learned. Masters
and Johnson (1963) have shown that practically
all stages of the orgasmic process differ between
males and females. Clitoral erection is comparatively slow during initial excitement; then the
clitoris retracts and essentially maintains a
"buried" position until the orgasmic phase has
passed. Only after the cessation of vaginal orgasmic contractions does the clitoris reappear
(Masters and Johnson, 1963). So although we
may speak of the penis and clitoris as homologous structures, their functioning is not parallel.
In truth, instinct is modified by learning as
much as learning is modified by instinct (Tinbergen, 1951; Verplanck, 1955; Deese, 1958).
The evidence may well indicate that while
among all species sex roles and the learning of
them are prenatally organized, such roles, particularly among humans, may be greatly modified though never fully negated. It is natural
to conclude that both biological and cultural
factors interact and meld to determine masculine and feminine gender roles (Dengrove,
1961). To say that learning predominates in
sex role assumption, when based upon evidence
from hermaphrodites, is unwarranted. All this
evidence may show is that hermaphrodites are
quite flexible in their assumption of a gender
role. The surprise or abnormality would be if
humans, whom we consider to be among the
highest evolved forms of life, could not greatly
modify instinctive behavior. To jump the gap
by extending the breadth of this modifiability
and to say that because of it man is completely
divested of his evolutionary heritage to instinctive mediation is specious.
Tinbergen (1951), in discussing the instincts
and causation underlying human behavior, said,
"Mating behavior in man, not in the form of
the accomplishment of the consummatory act,
but in the preparatory, appetitive stage of 'lovemaking' proves, when studied ethologically, to
be basically dependent on sex hormones and
on external stimuli and it is on these agents
that our rational powers exact a regulating influence." Beach (1949) has offered a basis from
which human sexual behavior may be studied
when he said, "To interpret the sexual behavior of men and women in any society it is
necessary first to recognize the nature of any
fundamental mammalian pattern and then to

167

discover the ways in which some of its parts
have been suppressed or modified as a result of
social pressures brought to bear upon the individual" (emphasis added).
The proper interpretation of human sexual
behavior must not stumble on a debate of nature
versus nurture. Undoubtedly both are significantly involved!
SUMMARY

The evidence and arguments presented show
that, primarily owing to prenatal genic and
hormonal influences, human beings are definitely predisposed at birth to a male or female
gender orientation. Sexual behavior of an individual, and thus gender role, are not neutral
and without initial direction at birth. Nevertheless sexual predisposition is only a potentiality setting limits to a pattern that is greatly
modifiable by ontogenetic experiences. Life experiences most likely act to differentiate and
direct a flexible sexual disposition and to mold
the prenatal organization until an environmentally (socially and culturally) acceptable gender role is formulated and established.
It is also indicated, on the one hand, that the
argument in favor of an imprinting type of
assumption of gender role is spurious for the
human being and that, on the other hand, learning theory cannot account for all observed sexual behavior. That imprinting does not account
for assumption of the gender role is shown by
the failure of the phenomena to meet the criteria for imprinting and by the inability of an
imprinting theory to handle various facets of
human behavior. That learning cannot account
for all sexual behavior was shown by reviewing
the original evidence, and by presenting clinical,
comparative cultural, and animal studies.
Instead, human sexual behavior is seen to be a
composite result of prenatal and postnatal factors. The evidence derived from human hermaphroditism, instead of constituting a separate
group of data from which a state of psychosexual neutrality at birth is to be inferred, can
perfectly well fit into the classical and phylogenetically consistent theory of sexual predisposition at birth. This conclusion is best seen
not when the evidence is atomized, and gender
role is compared with each atom of influence,
but when all the evidence is considered in toto.

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THE QUARTERLY REVIEW OF BIOLOGY

168

DEVELOPMENT
MODELSOF PSYCHOSEXUAL
+
BIASEDORIGIN
NEUTRALORIGIN

STAGES
CRITICAL
INDEVELOPMENT
-

CONCEPTION

A|

----

IlMALE

MALE

FEMALE

SEXUALI

FEMALE

-

DIFFER
ON
ENTIATI

/

BIRTH-----

----

-----------------

----------

CRITICAL I
EARLY

I

j

PERIOD

I

PUBERTY---------------

ADULTHOOD

B

---

-

-

I

--

WITHIN
LIMITSTO DEVELOPMENT
IMPOSED
ANDBIOLOGICALLY
ICULTURALLY
PREFERREDBEHAVIORSARE CONTAINED
WHIClH
INDIVIDUALLY
+

TO AVOID COMPLICATIONSWITHINTHE GRAPH ONLYTHE DEVELOPMENTALONGA MASCULINEDIRECTION
IS SHOWN. DEVELOPMENTOF A FEMALE WOULDBE SIMILAR BUT ON THE OPPOSITE SIDE.
FIG. 1.

MODELS OF PSYCHOSEXUAL DEVELOPMENT

A, Stemming from a psychosexual neutral disposition at birth; B, Stemming from a psychosexual
predisposition at birth.

Considering normal psychosexual development,
the two theories may be represented as in Fig. 1.
In Fig. 1, A, a psychosexually neutral origin
provides a narrow basis from which all the manifestations of sexuality are supposedly developed.
In comparison, Fig. 1, B depicts the comparatively broad basis of a sexually predisposed individual. The former theory postulates specific
imprints or learning experiences which would
enlarge and direct sexual development. The
latter need only postulate cultural restrictions
and learning to narrow and concentrate sexual
direction and orientation. As the figure indicates, there are various "critical stages" which
affect the range of subsequent sexual capability.
A theory of psychosexual neutrality sees these
stages as levels which remove the individual
further from the neutral midline. A theory of
psychosexual predisposition views these stages
as imposing limits and restrictions in the form
of culturally and biologically acceptable sexual
outlets within the total capability. To cross
from the male to the female "path" in Fig. 1,

A would mean to overcome a relatively broad
gap (indications of an irreversible change); for
malassigned individuals to cross over in Fig. 1,
B would require only transcending a culturally
imposed barrier to arrive on a different biologically "predisposed" path. All in all, the
second model (B) seems best suited to the available anthropological and clinical data, which
predicate the initial existence of a bisexuality
that is subsequently narrowed. [Chall (1963)
presents a scheme of levels which is an attempt
to depict graphically the determinants of human
sexual behavior.]
CONCLUSION

The theory of inherent sexual predisposition
and of a somatic basis for the patterning of
sexual behavior is not original with me. Aside
from mythological and religious beliefs of a
similar nature, this hypothesis was advanced
scientifically almost fifty years ago by Goodale
(1918). It was revived by Ball (1937) and