Some negative effects of stereotyping are decreased academic performance among those stereotyped and increased aggression among the stereotyped individuals. In addition, stereotyping leads to a lack of self-control, increased eating and a decreased ability to make rational decisions.
In one study, two groups of women completed a math test. In one group, the women received support and problem-solving strategies. In the other group, researchers fed the women negative stereotypes. After the test, the group that received negative stereotypes showed more hostility and performed poorly on cognitive tasks compared to the group that received positive support.
Another study linked stereotypes about athletic ability to poor performance. In the study, when a group of black people thought a test was about athletic intelligence, they performed poorly. However, when the group thought the test measured natural athletic ability, they performed well. In this way, a negative effect of stereotyping is decreased performance in physical and cognitive tasks.