To talk about stereotypes, one has to first define what they are. Stereotypes are simply beliefs about a group of people. They can be positive (children are playful) or they can be negative (bankers are selfish), or they can be somewhere in between (librarians are quiet). When stereotypes are defined as beliefs about groups of people (true or untrue), they correlate with real world criteria with effect sizes ranging from .4 to .9, with the average coming in somewhere around .8. (This is close to the highest effect size that a social science researcher can find, an effect size of 1.0 would mean that stereotypes correspond 100% to real world criteria. Many social psychological theories rest on studies which have effect sizes of around .2.)
Jussim and his co-authors have found that stereotypes accurately predict demographic criteria, academic achievement, personality and behaviour.7 This picture becomes more complex, however, when considering nationality or political affiliation. One area of stereotyping which is consistently found to be inaccurate are the stereotypes concerning political affiliation; right-wingers and left wingers tend to caricature each others personalities, most often negatively so.7
Lest one thinks that these results paint a bleak picture of human nature, Jussim and his colleagues have also found that people tend to switch off some of their stereotypes – especially the descriptive ones – when they interact with individuals. It appears that descriptive stereotypes are a crutch to lean on when we have no other information about a person. When we gain additional insights into people, these stereotypes are no longer useful. And there is now a body of evidence to suggest that stereotypes are not as fixed, unchangeable and inflexible as they’ve historically been portrayed to be.8