Eagly Karau. Role Congruity TheorySeveral studies have shown that women have to meet more / higher criteria to be judged as very competent and possessing leadership ability than men. Once women have obtained a position of leadership, their qualifications are rated as less, even if they have performed the same as men. These two forms of prejudice stem from a perceived contradiction between typical female traits (e.g. caring and helpful) and leadership traits (e.g. assertive and independent). For more background information read the entire article here.

Eagly, A. H., & Karau, S. J. (2002). Role congruity theory of prejudice toward female leaders. Psychological Review, 109, 573-598. https://doi.org/10.1037/0033-295x.109.3.573