The experiment by Hamilton and Gifford is helpful for showing us how racial and ethnic stereotypes may be formed and perpetuated. The experiment demonstrated that relatively rare events catch people's attention, and thus are more memorable.

Because members of minority groups are, by definition, less numerous than the majority group, and because criminal behaviors are less common than lawful behaviors, when a minority member commits a crime, it is a sufficiently rare event that it gets noticed and remembered. As members of the majority group are forming impressions of the minority group, these memorable incidents lead to illusory correlations between minority status and criminal tendencies, and thus influence the formation of negative stereotypes.

Of course, not all stereotypes are negative, and not all are unfair overgeneralizations. Some stereotypes are simply accurate beliefs about groups of people (such as "Males are generally taller than females") or overly favorable beliefs (such as "Women are generally nicer than men"). If stereotypes merely made us all feel good about each other, social psychologists would not be so concerned.