These aren't just stereotypes, concludes a study in September's Perspectives on Psychological Science (Vol. 3, No. 5). Rather, geographical placement is a good predictor of psychological characteristics.

The study, led by social and developmental psychologist Jason Rentfrow, PhD, at Cambridge University in England, examined more than half a million Americans. Rentfrow and his colleagues analyzed data collected from an online personality test that measured the "big five" personality traits: openness, conscientiousness, extraversion, agreeableness and neuroticism. The researchers also asked people about where they lived, their health, religiousness and values and social involvement.

They found that people with similar personality traits tend to cluster geographically. People appear to migrate to live with others who reflect their values, concludes Rentfrow, who adds that living around people with similar ideas in turn influences their own.

"People really are kind of different in Louisiana than they are in Massachusetts," he says.

The physical environment itself can have some effect, he says. For instance, research shows that people in hot climates tend to be more aggressive, and people who live in densely populated urban areas have higher rates of depression and stress.

This is important for social scientists and psychologists to keep in mind when conducting research, Rentfrow says. For example, someone studying attitudes about race might gather different results from people living in different parts of the country, which could affect that study's generalizablility.

—M. Price