By about age 12, students who feel threatened by mathematics start to avoid math courses, do poorly in the few math classes they do take, and earn low scores on math-achievement tests. Some scientists have theorized that kids having little math aptitude in the first place justifiably dread grappling with numbers. However, it is not that simple, at least for college students, according to a study in the Journal of Experimental Psychology. According to the study, people's intrusive worries about math temporarily disrupt mental processes needed for doing arithmetic and drag down math competence, report Mark H. Ashcraft and Elizabeth P. Kirk, both psychologists at Cleveland (Ohio) State University. Math anxiety exerts this effect by making it difficult to hold new information in mind while simultaneously manipulating it, the researchers hold. Psychologists regard this capacity, known as working memory, as crucial for dealing with numbers. "Math anxiety soaks up working memory resources and makes it harder to learn mathematics, probably beginning in middle school," Ashcraft says.