Brain and Cognition 45, 392–414 (2001) doi:10.1006/brcg.2001.1287, available online at http://www.idealibrary.com on Stereotypes and Steroids: Using a Psychobiosocial Model to Understand Cognitive Sex Differences Diane F. Halpern California State University, San Bernardino and Uner Tan Department of Physiology, Black Sea Technical University Medical School, Trabzon, Turkey To further our understanding of cognitive sex differences, we studied the relationship be- tween menstrual phase (via serum estradiol and progesterone levels) and cognitive abilities and cognitive performance in a sample of medical students in eastern Turkey. As expected, we found no sex differences on the Cattell ‘‘Culture Fair Intelligence Test’’ (a figural reasoning test), with females scoring significantly higher on a Turkish version of the Finding A’s Test (rapid word knowledge) and males scoring significantly higher on a paper-and-pencil mental rotation test. The women showed a slight enhancement on the Finding A’s Test and a slight decrement in Cattell scores during the preovulatory phase of their cycle that (probably) coin- cided with a rise in estrogen. There were also small cycle-related enhancements in performance for these women on the mental rotation test that may reflect cyclical increases in estrogen and progesterone. Additional analyses showed an inverted U-shaped function in level of estra- diol and the Cattell Test. Finally, for women who were tested on Day 10 of their menstrual cycle, there was a negative linear relationship between their Cattell scores and level of proges- terone. Stereotypes about the cognitive abilities of males and females did not correspond to performance on the mental rotation or Finding A’s Test, so the sex-typical results could not be attributed to either stereotype threat or stereotype activation. For practical purposes, hormone-related effects were generally small. Variations over the menstrual cycle do not pro- vide evidence for a ‘‘smarter’’ sex, but they do further our understanding of steroidal action on human cognitive performance.  2001 Academic Press The question of how to understand sex-typical patterns of cognitive abilities has important implications for psychologists and neuroscientists from a diverse array of backgrounds and theoretical orientations. A large body of research has shown that there are some cognitive tasks that show no sex differences, others in which the sex Address correspondence and reprint requests to to Diane F. Halpern, Department of Psychology, Cali- fornia State University, San Bernardino, 5500 University Parkway, San Bernardino, CA 92407. Fax: (909) 880-7003. E-mail: dhalpern@csusb.edu. We thank Simay Ikier for assistance with the Turkish language version of the Finding A’s Test and Dr. Marcia Collaer at Middlebury College for helpful comments on an earlier draft of this article. We thank the faculty in the Department of Psychology at Bosphorus University, Istanbul, Turkey, for support- ing the first author during her stay in Turkey and for assistance with the Turkish language and data collection. 392 0278-2626/01 $35.00 Copyright  2001 by Academic Press All rights of reproduction in any form reserved.