This study presents an experimental evaluation of a model that describes the constraining effect of cultural beliefs about gender on the emerging career-relevant aspirations of men and women. The model specifies the conditions under which gender status beliefs evoke a gender-differentiated double standard for attributing performance to ability, which differentially biases the way men and women assess their own competence at tasks that are career relevant, controlling for actual ability. The model implies that, if men and women make different assessments of their own competence at career-relevant tasks, they will also form different aspirations for career paths and activities believed to require competence at these tasks. Data from the experiment support this model. In one condition, male and female undergraduate participants completed an experimental task after being exposed to a belief that men are better at this task. In this condition, male participants assessed their task ability higher than female participants did even though all were given the same scores. Males in this condition also had higher aspirations for career-relevant activities described as requiring competence at the task. No gender differences were found in either assessments or aspirations in a second condition where participants were instead exposed to a belief that men and women have equal task ability. To illustrate the utility of the model in a "real world" (i.e., nonlaboratory) setting, results are compared to a previous survey study that showed men make higher assessments of their own mathematical ability than women, which contributes to their higher rates of persistence on paths to careers in science, math, and engineering.