The acquisition of avoidance behavior by male and female Holtzman rats was compared in a two-way shuttle box. The performance of both sexes was an inverted U-shaped function of US intensity and males performed more poorly at each of the four shock levels tested. At higher US intensities male performance was characterized by a marked intersession response decrement, a pattern rarely seen in female performance. Control experiments demonstrated that the sex difference was not related to differences in body weight, age, or reproductive experience. Females also had lower flinch and jump thresholds in tests of sensitivity to electric shock. Gonadeetomy in adulthood did not modify the avoidance behavior or sensitivity to shock of either sex, but testosterone injections in infancy, when combined with testosterone replacement in adulthood, produced females whose avoidance behavior was dramatically "masculinized."Although there is an extensive literature demonstrating that human males and females differ on a wide variety of tasks unrelated to reproductive behavior (Broverman, Klaiber, Kobayashi, & Vogel, 1968), experimental psychologists working with animals have shown little interest in assessing sex differences in nonreproductive behaviors or in attempting to identify the underlying physiological mechanisms. Indeed, the typical experiment is designed in such a way as to preclude the discovery of any sex differences that might exist. Nevertheless, reliable sex differences have been observed in running-wheel and open-field activity (Hitchcock, 1925; Levine & Broadhurst, 1963), aggressive behavior (Beeman, 1947), and saccharin preference (Valenstein, Kakolewski, & Cox, 1967).The present series of experiments examines sex differences in the acquisition of an active-avoidance response in relation to reactivity to electric shock, body weight, and the presence of gonadal hormones dur-1 Based on a doctoral dissertation submitted to the Graduate School

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Both patients with Parkinson's disease or chronic progressive multiple sclerosis and neurologically normal controls judged the emotional expression of faces from a standardized set of photographs. Both groups of patients were impaired on the affective judgment task and on Benton's Facial Recognition Test. Multiple regression analysis showed that performance on the facial recognition test accounted for 44% of the variance in performance on the affective judgment task, whereas scores on the Beck Depression Inventory did not predict the accuracy of affective judgments. Inaccurate judgments of affect by patients with Parkinson's disease or multiple sclerosis appear to have been secondary to their impaired ability to discriminate details of facial stimuli. Feinberg, Rifkin, Schaffer, and Walker (1986) have reported that patients with major depressive disorders were impaired in labeling emotional expressions of faces, but that they performed normally on tests of facial discrimination that did not require assigning emotional labels to faces. Depression is reported to be common among patients with Parkinson's disease (PD)

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