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This study describes the range and reliability of differences between individual elephant seal bulls, Mirounga angustirostris, on several parameters of the threat call: call type, spacing of pulses within calls, addition of snorts to calls, pulse rate of calls, and number of pulses in calls. In addition, some preliminary analyses of the social function of these individual differences are made. Two previously suggested hypotheses, that specific features of the call communicate dominance status and that differences in pulse rate represent dialects, are investigated.

Reliability and validity data are reported for a questionnaire measure of individual differences in dominance-submissiveness. The measure was based on an initial set of 457 items which was subsequently augmented by an additional 62 rewritten and new items. The initial pool of items, which was carefully constructed to assure broad generality, contained 64 content groups representing various aspects of dominance-submissiveness. The final 48-item dominance-submissiveness questionnaire, which was balanced for response bias, had high internal consistency (Kuder-Richardson formula 20 coefficient was equal to .95). It was independent of social desirability (correlated .08 with the Crowne and Marlowe social desirability scale). As the scale also satisfied the requirements of low correlations with measures of trait pleasure ( r = .14) and arousability ( r = -.10), it can thus be used with these two measures for a three-dimensional characterization of temperament. Correlations with other available measures of dominance were significant and high.

Threat vocalizations of adult and juvenile northern elephant seal ( Mirounga angustirostris ) bulls were studied and compared. Adult bulls displayed consistent individual vocal patterns. These vocal signatures may facilitate recognition of individuals within the male dominance hierarchy. The calls of juvenile bulls were more variable than those of adults. Juveniles frequently used more than one syllable type in their threats, and individual syllables were delivered at a variable rate. These characteristics were more common in younger than in older juveniles.

A quantitative analysis of the volume of 4 cell groups in the preoptic- anterior hypothalamic area (PO-AHA) and of the supraoptic nucleus (SON) of the human brain was performed in 22 age-matched male and female individuals. We suggest the term Interstitial Nuclei of the Anterior Hypothalamus (INAH 1–4) to identify these 4 previously undescribed cell groups in the PO-AHA. While 2 INAH and the SON were not sexually dimorphic, gender-related differences were found in the other 2 cell groups. One nucleus (INAH-3) was 2.8 times larger in the male brain than in the female brain irrespective of age. The other cell group (INAH-2) was twice as large in the male brain, but also appeared to be related in women to circulating steroid hormone levels. Since the PO- AHA influences gonadotropin secretion, maternal behavior, and sexual behavior in several mammalian species, these results suggest that functional sex differences in the hypothalamus may be related to sex differences in neural structure.

To investigate the possibility that serotonin plays a role in the sexually dimorphic development of a nucleus in the medial preoptic area of the rat brain, p-chlorophenylalanine, an inhibitor of serotonin biosynthesis, was administered to pregnant dams from day 8 of gestation until parturition. This treatment did not alter plasma steroid levels but increased the volume of the sexually dimorphic nucleus in female neonates to that of control males. Thus, serotonin is implicated as a neurochemical which may be involved in the sexually dimorphic development of the preoptic area.

The brain is known to control a variety of functions which differ in males and females. Many of these functions become irreversibly organized under the influence of hormones during particular developmental stages. Two of the best-studied sexually differentiated brain functions in a variety of animals are the patterns of gonadotropic hormone release and sexual behaviour. In developing foetal or neonatal mammals these brain functions are thought to possess an inherently female predisposition. They will remain female, unless male differentiation is actively superimposed by androgens or oestrogens during a critical period of sexual differentiation. In many animal models, like the rat, the organizational effects of androgenic hormones are thought to be mediated by intracellular conversion of these hormones in certain brain areas to oestrogens. Perinatal treatment of female rats with aromatizable androgens or with steroidal or non-steroidal oestrogens results in permanent defeminization and masculinization of sexual behaviour patterns and of gonadotropic hormone release (see Goy and McEwen 1980, Booth 1979, Plapinger and McEwen 1978 for reviews). Treatment of male rats perinatally with androgen antagonists or with oestrogen antagonists was shown to cause permanent feminization of sexual behaviour patterns and of the gonadotropic hormone release pattern (Neumann and Elger 1966, Plapinger and McEwen 1978, Booth 1979).

The volume of the sexually dimorphic nucleus in the preoptic area (SDN-POA) of the rat brain is severalfold larger in adult male rats than in adult females. This sex difference in brain structure was previously shown to develop under the influence of androgenic and estrogenic hormones during the perinatal period. We tried to clarify the differential role played by androgens and estrogens during development and differentiation of the SDN-POA by treating male and female rats during an extended pre- and postnatal period either with the estrogen antagonist tamoxifen or with the androgen antagonist cyproterone acetate. Treatment with tamoxifen did not alter serum levels of testosterone in male rats during the perinatal period, but it inhibited development and differentiation of the SDN-POA. Pre- and postnatal treatment of male rats with cyproterone acetate resulted in female phenotypic appearance, but it had no influence on differentiation of the SDN-POA. Perinatal treatment of female rats with tamoxifen resulted in permanent anovulatory sterility, but did not influence SDN-POA differentiation. Treatment of female rats with cyproterone acetate had no influence on SDN-POA differentiation or on the capacity to ovulate. Since pre- and postnatal treatment of male rats with cyproterone acetate is known from previous studies to femenize sexual behavior patterns and to retain the mode for cyclic gonadotropin release, and since the same treatment did not influence differentiation of the SDN-POA in the present study, it may be concluded that the SDN-POA is not directly involved in the control of female sexual behavior and in the control of the gonadotropic hormone release pattern.(ABSTRACT TRUNCATED AT 250 WORDS)

The volume of the sexually dimorphic nucleus in the preoptic area (SDN-POA) of the rat brain is several fold larger in males than in females. When female rats were treated pre- and postnatally with testosterone propionate (TP) or with diethylstilbestrol (DES) they became anovulatory and their SDN-POA developed equivalent in size to that of normal males. Identical treatment of male rats resulted in deficient testicular development, but had no influence on SDN-POA volume. The results indicate that the gross morphological sex difference in SDN-POA volume can exclusively be controlled by the hormonal environment during the critical period of sexual brain differentiation, and that non-steroidal estrogens are just as effective as convertible androgens in stimulating SDN-POA differentiation.

Sex-typed behavior was assessed at age 3 using the Pre-School Activities Inventory, and at age 13 using the Multidimensional Gender Identity Scale, in 54 masculine boys, 57 masculine girls, 75 feminine boys, 65 feminine girls, 61 control boys, and 65 control girls. At age 13, girls who had been masculine at age 3 felt less similar to other girls, were less content being a girl, and had greater self-efficacy for male-typed activities than control girls, and girls who had been feminine at age 3 had greater self-efficacy for female-typed activities. Boys who had been feminine at age 3 felt less similar to other boys and had lower self-efficacy for male-typed activities than control boys at age 13, and boys who had been masculine at age 3 felt more competent in agentic roles. Thus, sex-typed behavior at age 3 predicted sex-typed behavior at age 13. It was concluded that the degree of sex-typed behavior shown by preschool children is a good indicator of their degree of sex-typed behavior following the transition to adolescence.