been trained; they ranged in age from three to 12. Furthermore, all of the six cultures may well be sexist. Still, we can go younger. Annelise Korner has spent many years studying newborn infants, and one of her central interests has been sex differences. She, as well as other investigators, has found that at birth boys show more muscle strength — greater head lift in the prone position, for example — while girls show greater skin sensitivity, more reflex smiles, more taste sensitivity, more searching movements with their mouths, and faster response to a flash of light. But before we resort to this indirect accounting, it behooves us to consider another category of evidence: the sort of evidence that comes from studies of hormones, behavior, and the brain. The idea that humoral factors secreted by reproductive organs influence gender differences in behavior is very old; castration has long been used in attempts to reduce aggressiveness in animals and men, and systematic experimental work demonstrating that this works has been available since 1849. The question is no longer whether hormones secreted by the testes ' promote or enable aggressive behavior, but how, and also: What else goes on in a like manner? The principal male gonadal hormone in mammals is testosterone. It belongs to a chemical class known as steroids. The steroid class includes the two principal female reproductive hormones: estradiol — the key estrogen in humans — and progesterone, the gestation-promoting substance secreted in massive quantities by the placenta, and in lesser quantities, in the nonpregnant woman, by the ovaries. Estradiol and progesterone, together with the pituitary hormones that regulate them, participate in the determination of the monthly cycle. Although nothing so fabulous as that exists in males, there is much in common between testosterone’s mode of action and that of the two female sex steroids. The brain is the main regulatory organ in behavior, and behavior is that organ’s major output; for a molecule to affect behavior it must generally first affect the brain, or at least the peripheral nerves. Sex steroids are no exception. Giving a rat a systemic injection of estradiol (radioactively labeled for tracing) will produce a high concentration of this The community of scientists working in this field concluded that the basic plan of the mammalian organism is female and stays that way unless told to be otherwise by masculine hormones. hormone in certain brain cells — specifically, in their nuclei — within two hours. Twenty-two hours after that there will be a correspondingly massive increase in the tendency of the rat — if female — to respond to stimulation with sexual posturing. What happens in those 22 hours will tell a tale that may very well change the way we look at cell biology, but the tale cannot be told without at least a few more years of research. Meanwhile, we know, as children like to say, for sure, that sex steroid hormones affect behavior, and we know they get around quite well in the brain. Using radioactive labeling, it has been very easy to show not only that they pass from blood to brain, but they concentrate selectively in certain brain regions. That is, concentrations occur in brain regions that play an important role in courtship, sex, maternal behavior, and violence — just the behaviors in which the sexes most differ and the ones most subject to influence by testosterone, estradiol, and progesterone. Although the way the system works is scarcely understood, there are clues. For instance, injection of testosterone lowers the threshold for firing of nerve fibers in the pathway that leads to the hypothalamus, and as such in all likelihood mediates an excitatory influence on sexual and aggressive behavior. This finding gives substance to the action of testosterone on behavior. It is one thing to say that this hormone probably influehces sex and aggression by acting on the brain; it is quite another to find a major nerve bundle deep in the brain, likely to be involved in sex and aggression, that can fire more easily when testosterone acts on it than when it does not. A key link in the story has been formed. But we don’t even need to reach so deeply into the brain, Peripheral nerves have now been shown in several experiments to concentrate these hormones. In songbirds in which the male of the pair is the singer, testosterone is concentrated in the motor nerves to the syrinx — the bird’s voice box — and this is almost certainly part of the reason testosterone promotes song, which is a male courtship pattern. In female rats, injection of estradiol increase the size of the region of sensitivity of the nerve to the pelvic region, even when that nerve is detached from the brain; this is presumably part of the mechanism that makes the female susceptible — some of the time, anyway — to male advances. Such is the view of the physiologist, which is, not surprisingly, pretty unrelenting. What is a bit surprising is that someone like Alice Rossi has accepted it. Rossi is a family sociologist. After years of distinction in her field, she became dissatisfied with 19th-century sociologist Emile Durkheim’s dictum that only social facts can explain social facts and began to take seriously the notion that at least some social facts might be explained by biological ones. She has become adept in reading the biological literature, and when she reviews it for her sociologist colleagues, she does not attempt to conceal from them her belief that sorpe of the observed gender difference in social behavior — for example, in parenting — is attributable to causes in endocrinology. In reviewing the well-known sex difference in nurturing behavior — obvious particularly within the family, and in all cultures — Rossi has accepted the possibility that it may have its roots partly in hormonal differences. She has defended this viewpoint in several recent articles, in the scholarly as well as semipopular literature. From a hormonal perspective, nur- turance has not been as well studied as aggressiveness, in some ways the antithesis of nurturance. In many studies of humans and other animals, testosterone at least clearly enables and perhaps directly increases aggressiveness. While no one with any experience in this field thinks that there is a simple relationship between testosterone and aggression, most people now accept that some such relationship does exist. ^obcecTio^ oF THE NARCISSUS BULB KIT Everyone loves a gift that grows! KIT CONTAINS 3 paperwhite narcissus bulbs, gravel, growing instructions and glass flower pot. All you do is add water and watch them grow into beautiful, fragrant blossoms. 7.99 for late night dining University Bar & Grill 4553 University Way NE. Seattle, Washington SERVING CONTINENTAL CUISINE UNTIL 1 AM WINES BY THE GLASS 632-3275 110 So. 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