Hunter-gatherer communities are relatively strong in their situational strength. This may help to illuminate why people in complex societies have peculiar personality structures. The evolutionary biologist Joseph Henrich and others have pointed out that although psychologists have long thought there were five personality factors, researchers have failed to identify the Big Five dimensions in non-student adult populations in Bolivia, Ghana, Kenya, Laos, Sri Lanka, Vietnam, and Macedonia, among other non-WEIRD locations. Instead, researchers often find only two: