College students were asked to read a story about a rather daft person, and then take a test. They did worse on that test than a control group that read a story about a non-idiot:
Sixty-three Austrian students read "Slow on the Uptake," about Meier, who wakes, is confused by an adage on his calendar, gets drunk, attends a soccer match and misses the outcome because he brawls. The students either summarized the story or underlined passages where Meier differed from them. A control group of 18 read a story with an innocuous protagonist.
Afterward, on a difficult test covering geography, science and the arts, the students who had read about Meier but not underlined how he differed from them scored from 30% to 32%, compared to about 37% for the control group and for students who distanced themselves from the character.
Hollywood mentioned this tendency a few years ago.
Link -via Althouse | Image: Despair
Telling women they are not as good at maths than men results in poorer scores of women in maths tests.
It has even been found that merely having to write your race before commencing in an intelligence test results in poorer scores for African Americans due to "stereotype threat", an effect that disappears when they are not required to write down their race. This has been offered as an explanation for the apparent poorer scores of African Americzns compared to white Americans in IQ tests.