Similarity-Attraction Effect

Similarity-Attraction Effect Definition

Similarity-Attraction EffectThe similarity-attraction effect refers to the widespread tendency of people to be attracted to others who are similar to themselves in important respects. Attraction means not strictly physical attraction but, rather, liking for or wanting to be around the person. Many different dimensions of similarity have been studied, in both friendship and romantic contexts. Similarity effects tend to be strongest and most consistent for attitudes, values, activity preferences, and attractiveness. Personality similarity has shown weaker, but still important, effects on attraction.

Similarity-Attraction Effect Background and Modern Usage

Similarity-attraction research embodies the popular adage, “birds of a feather flock together.” This effect has been studied extensively, usually in one of two ways. First, in laboratory experiments, participants are given descriptions of a person they are about to meet. These descriptions are manipulated to vary in their degree of similarity, from very similar to very dissimilar, to the participant’s own standing on whatever dimensions the investigator wishes to study. The second method entails correlational studies, which assess the properties of interest in relationship partners, often by questionnaire. The degree of correspondence between partners is then compared with that of random pairs of people, people with a tepid attraction to each other or, more commonly, chance. Years of research have produced such robust evidence that one researcher referred to the effects of similarity on attraction as a “law.” In striking contrast, many attempts to find support for a sister principle, known as the complementarity principle (“opposites attract”) have failed to find more than a highly selective effect in limited contexts.

Why does similarity attract? At least four explanations have received consistent empirical support. First, because similar others are more likely than are dissimilar others to possess opinions and worldviews that validate one’s own, interaction with similar others is a likely source of social reinforcement. Second, all other things being equal, people more readily expect rejection by dissimilar others than by similar others. As other research has shown, anticipated rejection usually diminishes attraction. Third, interaction with similar others may be more enjoyable than interaction with dissimilar others, inasmuch as similar others tend to share one’s own interests, values, and activity preferences. Finally, fortune or chance also seems to play a part. Because attitudes and values direct much of a person’s behavior (for example, people who love baseball attend more baseball games than people who don’t), he or she is simply more likely to encounter others who have similar attitudes and values than others with dissimilar preferences. Obviously, attraction cannot develop between persons who have not encountered each other. Overall, all four of these explanations likely contribute to the effect of similarity on attraction.

People sometimes question evidence about the similarity-attraction link for subjective reasons. After all, when a person reflects on his or her own friendships, he or she often notices the differences more than the similarities. This is probably a healthy part of the process of expressing and accepting one’s individuality. However, similarity is relative. When asked to consider the degree of similarity between the self and a close friend, compared with the self and a random inhabitant of planet Earth, or, for that matter, a random person living elsewhere in the same country, state, or neighborhood, the relevance of similarity for friendship usually becomes quickly apparent.


  1. Berscheid, E., & Reis, H. T. (1998). Interpersonal attraction and close relationships. In S. Fiske, D. Gilbert, G. Lindzey, & E. Aronson (Eds.), Handbook of social psychology (Vol. 2, pp. 193-281). New York: Random House.
  2. Newcomb, T. M. (1961). The acquaintance process. New York: Holt, Rinehart & Winston.