From the 1930s through the 1930s, the Committee for Research in Problems of Sex turned its support to studies of sexual behavior in animals and humans. Frank Ambrose Beach emerged as a young scientist in the 1930s and, by the mid – 1940s, had articulated a detailed theory of animal sexuality. As an undergraduate Beach had abandoned all hope of understanding human psychology, deciding that ‘‘white rats were simpler,’’ although he still wanted to solve basic problems in psychology. For his Ph. D. he damaged specific areas of the brain’s cerebral cortex to see if he could perturb maternal behavior in rats. From there to the study of hormones and sexual behavior was a short jump. During and just after World War II, Beach and other students of animal psychology accomplished three tasks.50 They detailed behaviors that they could quantify and designate as masculine or feminine; they developed some sense of behavioral differences among different species and among individuals of the same species; and they studied the effects of estrogen, progesterone, and testosterone on adult sexual behaviors. In synthesizing the results of such experiments, they articulated a vision of the origins of animal masculinity and femininity, one that many researchers eagerly applied to humans.
In this discussion I highlight three aspects of Beach’s work. First, he insisted on the diversity of animal behavior—within each sex, within each species, and among different species and genera. Second, he took what we would today call a systems approach to animal behavior, emphasizing the interactions among the varied physiological systems within each body, as well as the social context eliciting or permitting particular behaviors. Third, he was an outspoken liberal on the topic of human sexual diversity. In looking at his career and ideas, we can once again see clearly how the social and the scientific form part of a single fabric.
In a remarkably prolific four-year period, Beach reported in at least fourteen scientific papers on the results of his research on rat sexuality. Not surprisingly, he found sex differences in the control of male and female mating behaviors. When a female rat feels amorous, she characteristically darts, hops, and vibrates her ears. When the male mounts her, she flattens her back, raises her rump, moves her tail to one side, and permits copulation (see figure 8.1). The rump raising and presenting are a reflex action also inducible when an experimenter strokes a female rat’s back. The technical name for this response
figure 8. і: Mating and lordosis in the laboratory rat. A: The male investigates to determine whether the female is in estrus. B: If she is in estrus, the male mounts and clasps his forepaws around her hindquarters. This tactile stimulation causes her to move her tail to one side and arch her back (lordosis). C: The male dismounts and grooms himself. D: After several mounts, the male ejaculates. (Photos courtesy of Julie Bakker)
is lordosis. A willing male smells and licks the female’s genitals, and, if she permits, mounts her, introduces his penis (intromission), and thrusts deeply. He may repeat this behavior as many as 10 times before ejaculating. After each intromission, he rapidly withdraws and licks his genitals. To the experimental psychologist, each of these separate actions provides an opportunity to subdivide mating into parts that may be counted and analyzed for the possible influences of hormones, environment, and life experience.51 For each sex, the suite of behaviors defines masculinity or femininity with regard to mating.52 But just as noteworthy as differences between the sexes were the striking individual differences within each sex, among laboratory strains of the same species, and among rodent species. Neurologically, Beach argued, all animals have a bisexual potential. What, he wanted to know, were the factors that lead to particular sexual expressions, be they heterosexual matings, male-male mountings, male lordosis, female-female or female-male mountings?
Beach and other animal sex researchers had to defend both the importance and the propriety of their work. During the 1940s and ^os, psychoanalytic
‘‘environmental’’ theories of human development were far more popular than biological interpretations of behavior. Especially during the 1950s, human psychology had been strongly marked by psychoanalysis.53 To comparative animal psychologists, however, Freud seemed frustratingly ungrounded in quantitative, experimental biology. Animal psychology had developed in the United States following the lead of John B. Watson and others,54 while in Europe ethologists such as Konrad Lorenz dramatized the concepts of ethology with experiments on imprinting in birds. His famous photographs ofbaby ducks and geese following him around as if he were their parent, because he was the first moving object they saw upon hatching, captured the imagination of many in the United States. In general, students of both human and animal psychology had stressed the importance of experience and learning combined with the idea of instinctive, inborn drives (hunger, sexual desire, and so on) in the shaping of behavior. Now endocrinologists and physiologists hoped to swing the pendulum back toward biology.55 Furthermore, sex itself was not a topic for polite company.56 Such an unfavorable atmosphere may explain why Beach opened his major 1942 paper on the attack. ‘‘Students of animal behavior,’’ he wrote, ‘‘have often speculated upon the nature of sexual excitement, and schools of psychological thought have been founded upon ambiguous concepts of the human ‘sex drive.’ ’’ Beach intended to put the discussion on a scientific footing and to offer a ‘‘phylogenetic interpretation of human behavior.’’57
Beach provided a multilayered, sexually diverse model of animal behavior. Many vertebrates, he noted, were born with the nerve-muscle circuits (motor patterns) needed to solicit and execute the sex act fully formed. Male rats, for example, did not normally mate until they were thirty-five to eighty days old. But testosterone injection at much younger ages elicited a full range of adult behavior. Evidence for innate motor patterns did not, however, extend to the great apes. Here, it seemed, practice and experience were central to the ability to copulate, a fact of particular importance for Beach’s ‘‘phylogenetic interpretation of human sex life.’’
Being born with the basic circuitry, however, was not enough—especially since Beach thought the motor patterns for both masculine and feminine mating responses were present in each sex. How did one pattern come to dominate in a particular individual? Perhaps an answer could be found by analyzing the components of sexual arousal. Beach emphasized a holistic approach to such analysis.58 Arousal, for example, resulted from the particular constitution of the individual rat,59 the potency of stimulus objects, and the animal’s prior experience. Just as individual males varied in their interest in mating, particular females differed in their receptivity. Both mattered if a mating were to take place. An indifferent female and a less than enthusiastic male might fail to get it on. But couple a low-energy male with a highly receptive female, and sparks flew.60
Beach analyzed the inclinations of the mating couple. Prior experience mattered. Males segregated for long periods with other males were far less likely to mate than ones raised in isolation or with females. The senses mattered. The receptive female presented males with a veritable cornucopia of stimuli—movement, body postures, ear vibrations, smell, taste, touch— that all contributed to getting the male excited enough to mate. Rob a male of one of his five senses and he would still mate. But knock out more than one, and he pretty much lost interest.61 Although it was not clear how,62 the brain—Beach suspected the cerebral cortex—was also necessary for mating. And last, but not least, hormones mattered. Hormones could increase an animal’s general excitability by increasing its sensitivity to stimulating signals (all that odor, ear-wiggling, and hopping about).
Both testosterone and estrogen had sexually nonspecific effects. Injecting inexperienced male rats with testosterone, for example, got them so excited that they tried to mate with nonreceptive females, young males, and even guinea pigs!63 Injecting testosterone into female rats also increased their general excitability, as well as their tendency to exhibit both male and female mating patterns. But even untampered-with female rats would sometimes execute male mating patterns—mounting and thrusting on other animals, both male and female.64 Estrogen could also induce male mating patterns in both sexes and, of course, derived its name from its ability to produce estrus in female rodents. Beach insisted on ‘‘the absence of a perfect correlation between the hormonal condition of the animal and the character of the overt behavior.’’ Even rats were not mere slaves to their hormone levels. ‘‘Psychic factors’’ mattered, albeit not to the same degree as for humans.65
In his 1942 review article, Beach used a diagram to unify the pieces of the puzzle: the sensory inputs, the role of the central nervous system, and the function of hormones (figure 8.2). He hypothesized a Central Excitatory Mechanism (C. E.M.), a group of nerve cells that received incoming information from sense receptors and sent outgoing signals to the neural circuits that executed the male and female mating patterns. Different incoming receptors stimulated different numbers of nerve cells in the C. E.M. Thus, smell might be more important than vision. But the effects in the central mechanism added up.66 Smell alone might not increase excitation to the point where a signal left the center and stimulated mounting or lordosis. Or it might be enough to stimulate mounting, but not intromission. But additional stimulation from other sense receptors could put the excitation level over the top. Hormones,
figure 8.2 : Beach’s model of the mechanisms by which hormones affect behavior. (Beach 1942b, p. 189; reprinted with permission)
in Beach’s scheme, played three roles. First, they could act directly on the C. E.M. to stimulate the level of sexual excitement. Second, they could lower the threshold needed to stimulate the circuits governing the male or female behavior patterns. Third, they could directly affect the senses. Beach suspected, for example, that testosterone increased the tactile sensitivity of the penis.67 The penis’s touch receptors would send more intense signals back to the C. E.M., further stimulating the rat’s sexual excitement.
In Beach’s scheme, males and females differed quantitatively but not qualitatively. Androgen could stimulate female mounting and thrusting, for example, but not as easily as it could in a male. A female with especially sensitive sense receptors, for example, might need less androgen or estrogen to reach a state of sexual excitement than one with less sensitive or fewer receptors. Beach’s hypothesis accounted nicely for individual variability within each sex, as well as for the fact that both sexes could, under some conditions, display both masculine and feminine mating patterns and, finally, that both androgen and estrogen could induce either of these patterns in either sex.
Beach did much of his early work at the American Museum of Natural History in New York, but by 1946 his growing reputation led Yale University to hire him as a member of its Department of Psychology. From that position of authority, he actively promoted his ideas about animal sexuality. In 1948,
Beach delivered the prestigious Harvey Lecture in New York. Emphasizing the similarity of males and females, he noted: ‘‘The physiological mechanisms for feminine sexual behavior are found in all males and those for masculine behavior exist in all females. . . . Human homosexuality reflects the essentially bisexual character of our mammalian inheritance.’’68 Human societies may condemn the immorality of homosexual behavior, Beach wrote, but one could not appeal to nature as a justification: our mammalian ancestry proved homosexuality to be quite natural.
Beach’s animal research intertwined with the broader social discussions of human sexuality. He did most of his work on animal bisexuality just before and during World War II. Just after the war, he began to apply his ideas to humans, at a moment, he wrote, when ‘‘public attitudes toward open discussion and scientific exploration of problems relating to sex had become remarkably lenient, if not enlightened.’’69 The importance of his work seemed greatly strengthened by Kinsey’s findings of extensive bisexual behavior in men and women. In 1946, Beach acknowledged access to Kinsey’s as yet unpublished results,70 but since Beach knew Kinsey and was one of his interviewers,71 it is likely that he had been thinking about the work on humans since the early 1940s.72 In turn, Kinsey repeatedly cited Beach’s animal studies in order to locate human behavior within the panoply of normal mammalian biology.73 The war itself made homosexuality more visible.74 At the same time, Beach did experiments on rats that suggested a remarkable range ofsexual behaviors, and he interviewed humans about their sexual behaviors. At least through the early 1950s Beach’s views remained compatible with elements of the national discussion.75