Society knows well that males outperform females on mathematics portions of college entrance examinations. In 2003, for example, males scored an average 537 points on the mathematics section of the Scholastic Aptitude Test, while females averaged 503. Less well known is that males also show a slight advantage on the verbal portion. These gaps appear to be closing, but are still a significant source of concern for students, parents, and educators alike. Why the sex differences in standardized test scores? Some researchers suggest biological factors. For example, males may perform better on math tests because they are exposed to hormones in the womb that lead to enhanced functioning in the parts of the brain that contribute to spatial reasoning abilities, which are important in solving many math problems. Worrying was, however, related to negative outcomes for girls, including low levels of academic confidence and high levels of uncertainty about how to be successful. Low confidence and high uncertainty are likely to interfere with females' ability to perform at their best in testing situations. One theory is that females are more likely to feel poor performance is the result of uncontrollable factors, such as low ability. A second theory is that females are more concerned than males with pleasing others, including their parents, elementary and secondary school teachers, and school counselors. A third theory is that females may be more likely than males to experience anxiety in competitive environments. As a group, females are socialized to be cooperative, whereas males are socialized to be competitive. Claude Steele's "Stereotype Threat" theory is especially helpful in explaining why females perform worse on math portions of college entrance exams. Three basic premises that guide Steele's theory are discussed.