Some might think it presumptuous in today’s scientific and political climate to produce a book called Males, Females, and Behavior: Toward Biological Understanding. The reasons are apparent enough. Scientifically, there is such a wealth of materials that warrant inclusion—from pregnancy and health considerations to intellectual abilities and sports—that a series of volumes would seem more appropriate and the selection process horrendous. On the other hand, the political climate makes any inclusion in such a publication subject to criticism, justified or not.

The selection process was not so difficult. The choice of material was narrowed by this book being part of the culmination of a meeting held in Minot, North Dakota, under the auspices of Lee Ellis and Minot State University. It was made possible by a generous grant from the Eugene Garfield Foundation. The name of the meeting was the “International Behavioral Development Symposium: Biological Basis of Sexual Orientation and Sex-Typical Behavior.” Among its more notable features, the meeting was truly international—contributors attended from Australia to the United Kingdom—and the invitees were of stellar caliber. All had earned their way by publication and reputation. The presentations were first rate, and this volume contains expanded versions of many of them.

Presumption aside, it may be that such a book is not only needed but also potentially required reading for many. Consider this statement from a recent position paper of the American Academy of Pediatrics (1996). “Research on children with ambiguous genitalia has shown that a person’s sexual body image is largely a function of socialization, and children whose genetic sexes are not clearly reflected in external genitalia can be raised successfully as members of either sex if the process begins before 2½ years.” The assumption this august group seems to make is that the only biology that counts is that of the genitals; other sex differences are a function of socialization. This group is not alone.

The sociologist John Gagnon (1977) has written, “At the present time the belief in powerful [biological] sex drives seems quite implausible. Most psychologists … prefer to argue that human beings are active and energetic organ- isms that are capable of learning how to be sexual in the same ways that they learn everything else. What we need to do is begin to look at how the environment promotes or does not promote various kinds of sexual activity” (p. 11). Many sociologists are more accepting than Gagnon of a biological influence to male and female sex differences and similarities, but it is probably safe to say that by the nature of their profession most attend to those factors of behavior influenced by social conditions (see Sanderson & Ellis, 1992).

There is no argument by those associated with this book that socialization and learning processes are involved in how one behaves sexually. They would, nevertheless, argue that the body and mind individuals bring to the society, culture, and schools are not neutral. From the moment of birth, people typically come to the scene ready to interact with the world as either males or females (Diamond, 1965).

The political climate I referred to is the criticism on the part of feminists, many professionals of the humanities and social sciences, and others suspicious of a biological framework for the understanding of behavior (see, e.g., Ellis, 1996a). These critiques typically question why some studies are included and not others. More often, they argue that claims of sex differences, which seem invariably to come from studying men and women in the context of biology, are either unimportant or neglectful of social factors and are usually used to the detriment of women and other minorities. Certainly it is true that biologically oriented proclamations in science have not always proved kind to these groups.

Those that critique biologically related studies come in all stripes but often divide into two camps in regard to the studies themselves. Meredith Kimball (1995) described these two as the “similarities tradition” and the “differences tradition.” Both traditions challenge biological findings with the goal of improving the lot of women and eliminating what they see as their subordination. Those in the similarities school basically ignore erotic and reproductive behaviors and concentrate their attention on behaviors related to intellectual and social competency (see, e.g., Unger, 1989; 1992). Within these areas they believe differences either do not exist or are too small to be meaningful to explain existing gender differences in public and private life. Whether males are better at math than females is a common battleground here (see, e.g., Benbow & Lubinski, 1993; Hyde, Fennema, & Lamon, 1990).

Those in the differences school accept a bimodal skewing of behavioral characteristics among men and women but contend that the positive behaviors or characteristics of women have been undervalued or unappreciated in favor of those more often demonstrated by men. Nancy Chodorow (1978), for instance, uses psychoanalytic reasoning and Freudian theory to make this point; but more often it is argued with references to everyday experiences. For instance, J. C. Tronto (1987; 1993) considers “care-giving” as a behavior with notable sex differences. She argues that little attention is given to women’s greater involvement in nurturing and care giving since such behavior is taken for granted and does not garner high status. In any case, professional and lay interest does indeed focus on studies related to sex differences and similarities between males and females in regard to their behaviors.


Traditionally, from Biblical days until relatively modern times, the sexes were thought different and similar in ways to complement God’s plan or “nature’s way.” Serious questioning of these features did not come to the fore until the work of Charles Darwin (1871) who saw sex differences as crucial for his theory of evolution. It was Sigmund Freud, however, who focused his, and the Western world’s, attention on sex differences among humans.

Freud proposed a relationship between an individual’s genital anatomy and his or her psychosexual development (Freud, 1925; 1953). Terms like the Oedipal and Electra Complex, incest taboo, and penis envy came to represent theoretical frames within which behavioral differences between the sexes could be accounted for. Freud contended that males and females were biologically different but that their intellectual and behavioral development was parallel until awareness of the phallus. The boy becomes aware that the female does not have a penis and worries that his too might be removed (castration anxiety). The female realizes she doesn’t have a penis and wishes she did.

Female analysts challenged Freud. For example, Melanie Klein (1975) saw male and female behavioral differences stemming from conflicts between the girl and her mother not the presence or absence of a penis. Karen Homey’s (1926) work in particular emphasized attitudinal differences between the sexes. She attributed them to distinct developmental paths for women, which emphasized their feminine traits of cooperation and altruism. As remains true of psychoanalysis today, no experimentation was involved. In-depth case studies were the window to understanding.

While the analysts argued within the purview of medicine, first anthropologists and then sociologists were arguing the role of culture and society in structuring sex differences or similarities. Every new culture found was probed for similarities and differences between the sexes. The cultures were coded for their sex roles; work, marriage, and sexual patterns; and so on. For these early anthropologists, male—female biological differences were accepted as given; and they took as their duty to see how each society accommodated to them (Lee, 1976). It was the accommodations which took center stage.

Behavior patterns of males and females were studied to see how they were adaptive, learned, used, misused, similar or different cross-culturally, and so forth. In her classical study of three societies, for instance, Margaret Mead (1935) emphasized cultural determination of and differences in what she termed sex temperament. Barry, Bacon, and Child (1957), on the other hand, studying achievement and self-reliance, emphasized the similarities among societies. The question quickly developed whether those patterns of behavior seen as cross-culturally nearly universal are genetic (biological) givens or a function of nearly universal cultural practices. When many exceptions to a practice were found, the practices were termed cultural or learned traits; and when few exceptions could be found, they were considered innate and biological.

Much of the work of animal behaviorists in the United States and ethologists in Europe and the United Kingdom was directed to understanding sex differences. With Darwin as a stepping stone, animals were studied, not only to better understand them but also for what they could tell us about humans. The work of ethologists Konrad Lorenz and Niko Tinbergen (see, e.g., Tinbergen, 1951) and animal behaviorists such as Frank Beach, Dan Lehrman, Harry Harlow (see, e.g., Harlow, 1965), and others became known for this work. This area of research, unlike that of the analysts or anthropologists, depended heavily on experimentation along with observation.

The ethologists put their findings of sex differences and similarities in the context of evolutionary adaptation and ecology. Behaviors are seen to evolve just as structures do; those that are advantageous tend to be perpetuated while those that are disadvantageous die off. The animal behaviorists concerned themselves less with the evolutionary nature of the behaviors they studied but directly asked how certain behaviors came about or could be modified. Perhaps most important in the study of sex differences and similarities, both these scientific groups directly studied and experimented with animal reproductive behaviors such as courtship, mating, and parenting. The zoologist Jean Piaget (see, e.g., 1952; 1972) followed in the ethological mode but with an interest in human adaptation. He directly observed developing children in controlled circumstances. He considered the individual’s cognitive and intellectual development the key to adaptation. In so doing, he attended primarily to commonalties but also noted sex differences.

The work of psychologists like Louis Terman and Catharine Miles, L. B. Ames and L. Francis, Arnold Gesell, and later Eleanor Maccoby might be said to have ushered in the early psychologist’s exploration of human sex differences and similarities. At first a great deal of attention was focused on gender stereotypes and childhood development. For instance, from their research Terman and Miles (1936) constructed so-called male-female scales where male and female were seen as polar opposites; the more male one was, the less female, and vice versa. Later Terman (1946) expanded on this work in a major review entitled: “Psychological Sex Differences.” Gesell and colleagues (1940), in their classic work, extrapolated scales of development in which boys and girls were measured in characters ranging from block-building to walking to drawing. Increasingly the focus was on the development of intellectual performance and cognitive skills, personality traits, and attitudes and social behaviors. Psychologists like Lawrence Kohlberg (1966) and C. Gilligan (1982) even probed how the sexes compared in moral development. It was rare that sexual behaviors per se were investigated.1

Indeed, the older psychological studies mentioned, as well as most others (see, e.g., Maccoby, 1966; Maccoby & Jacklin, 1974) might better be termed gender rather than sex studies. The questions basically asked: How did boys and men differ or agree with girls and women on various characteristics—in their attitudes, modes of thinking, behaviors, and traits in nonerotic or noncopulation-related matters? Also, more often than not, the psychological research tended to focus on differences more than similarities. Differences were intuitively expected. In reviewing studies of sex and gender, Kay Deaux has written: “The accepted terminology itself suggests a belief in the existence of such differences, and failures to find difference are less often regarded as evidence of sex similarities than as a state of confusion or uncertainty” (1985, p. 54).

Research, particularly over the last two decades, on how biology affects the sexes seemed to multiply and diverge into several directions. Investigations, particularly by those using newly developed sophisticated techniques, have probed deeper into questions of male-female similarities and differences in actions, roles, attitudes, capacities, thinking, and more. Male and female characteristics and behaviors and masculinity and femininity traits are no longer seen as polar opposites but as overlapping and multidimensional (see, e.g., Constantinople, 1973; Bem, 1974; 1995). It is now widely accepted that one can have simultaneously male and female or masculine and feminine features.


David E. Comings has demonstrated that many syndromes that might be considered unrelated to sexual behavior may have genetic links to such behavior. For instance, the neuropsychiatric conditions known as Tourette syndrome and attention deficit hyperactivity disorder are both associated with genetic loading so that sex drive, sexual orientation, exhibitionism, and other behaviors are displayed proportionate to the number of related genes for these conditions seen in probands, relatives, or nonrelated controls. The implications of this are great. Physicians and lay persons alike typically overlook sexual signs of disease progression or remission in syndromes not obviously or intuitively related to sex. A wider view to disease with concern for the erotic is obviously called for.

Robert H. Lustig describes distinct male and female paths of brain cell development dependent upon the hormonal stimulus of androgen or estrogen stimulation; androgens promote axon development while estrogens promote dendritic development. Lustig’s work augments research of others like Juraska (1990), who found that the type of environment in which animals spent their early life shaped the length and branching of their cortical nerve cells, and did so differently for males and females. Lustig extrapolates that these differences can affect typical male and female development. It makes me wonder if such factors can account for the behavior of androgenized women with congenital adrenal hyperplasia or men feminized by hypogonadism or DES exposure.

Alan F. Dixson, Gillian R. Brown, and Claire M. Nevison investigate the postnatal surge of testosterone seen in human and nonhuman primates. Their findings that penile growth is promoted by this postnatal androgen is clear. However, contribution of this surge to sex differences in behavior was not seen. The full effect of this surge and its relevance to behavior—to humans in particular—thus remains open. With such a dramatic physiological phenomenon, I suspect this area of research will have more to tell us in the future.

Geoff Sanders and Deborah Wenmoth find a complicated relationship between hormonal effects on verbal and visual tasks measured over the menstrual cycle and linked to hemispheric laterality. They further show that these relationships are not unlike those seen in men if estrogen titers are taken into account.

If you are an environmentalist, you will appreciate the work of György Csaba. His experiments demonstrate that sex behavior can be critically affected by different medicinals and environmental pollutants. While these effects in humans have not yet been demonstrated, their clear-cut effects on animal models is cause for concern. Csaba uses the term “hormonal imprinting” to describe a one-time influence that has continual and long-term consequences. One can compare it to the genetic process known as “genomic or parental imprinting” (see, e.g., Surani, 1991). One is again struck by the crucial influence of early biological events in organizing later behaviors (see, e.g., Diamond, Binstock, & Kohl, 1996).

The area of neurotransmitters and its analogs was reported on by Elaine M. Hull and her colleagues, Catherine A. Wilson and her coworkers, and Ilona Vathy. The Hull group demonstrated the influence of paranatal dopamine agonists or inhibitors, the Wilson group did similarly with serotonin, and Vathy showed the effects of morphine. All these scientists show that these drugs have the capacity to differentially organize the brains of males and females and thereby affect their later sexual behaviors. Of added significance is that nonsexual behaviors (e.g., exploration and agonistic behaviors) were also differentially organized.

Katharine Blick Hoyenga and her colleagues report on their use of drugs that manipulate brain serotonergic activity and look for association between gender, narcissism, and other personality traits and tendencies. In doing so, they also attempt to integrate competing theories of personality and evolution.

Studies of twins seem always to have their own fascination. Edward M. Miller uses twin sets to fathom the transplacental influences of a shared hormonal uterine environment. His analysis indicates that women who shared their mother’s womb with a brother have more masculine attitudes, abilities, and behaviors than those who shared the pregnancy with a sister.

Nancy L. Segal uses twins in a quite different way. She analyzes sex differences in the ways brothers and sisters experience grief and confirms suspicions that surviving females have significantly higher levels of grief than males.

Richard Lippa used a new analysis technique he developed to study intellectual giftedness as manifest by National Merit Test scores. His findings indicate that sex nonconformity, rather than conformity, seems associated with academic achievement. This nonconforming seems to be stronger among girls than among boys. Parents might now worry less when seeing their children following a different drummer.

It had been widely held that many sexually dimorphic behaviors are distinct between the sexes, not in kind or motive but in the sense that one sex demonstrates the behavior more often than the other. Some attributed this to differences in threshold for the release of the behavior. In a new approach to this area, Evelyn F. Field and Sergio M. Pellis demonstrate that there is much more to this subject. In analyzing play fight behavior in rats, they find only the gross manifestation of the behavior can be said to be similar between the sexes. They report at least five kinds of sex-specific mechanisms that interact to produce the observed sex differences in play fighting.


The studies presented in this book are bound to be relevant to the real world as science continues to probe the complex mysteries of sex differences and similarities in behavior. They are also relevant in ways different from those that would follow from the pronouncement of the American Association of Pediatricians. A case study I coauthored with H. Keith Sigmundson (1997) seems to encapsulate aspects of male and female biology, psychosexuality, the role of the social environment, and human behavior. The case is that of a boy who, following an accident that removed his penis, had his scrotum and testes surgically removed and was then raised as a girl. This management was predicated on the theory that all significant gender features of importance could be imparted by socialization and, in the absence of a penis—with its relevance to social status—make impossible development as a male.

Despite the best of efforts by family and therapists to induce this XY individual to accept life as a girl, the experiment failed. At puberty, the individual reassigned himself to live as a boy. We interpret this as evidence of innate biological forces in sexual identity development sufficient to overcome the extensively imposed environmental influences. The role of the environment, especially of his peers, was significant, however. They provided standards of behavior patterns and other comparisons from which John (pseudonym) could see that he fits in better as a boy than as a girl. I believe everyone evaluates similarities and differences to gauge his or her own place in the sexual and gendered world (Diamond, 1997).

Let us hope that the present volume will add to the ease with which we all come to manifest and understand both our gender and our sexual identities.


1 Ounsted and Taylor (1972) offer an update on some human biological differences of interest up to the 1970s; and Lee and Stewart (1976) provide an excellent anthology of writings on the early study of sex differences and similarities from Freud to Maccoby. Lately, many psychologists study evolutionary theory, as had the biologists earlier, in attempts to understand sex differences and similarities (see, e.g., Allgeier & Wiederman, 1994; Buss, 1994).

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