ChangHyun Jin: e-mail: chjin@mail.utexas.edu |UT: At Austin: http://www.utexas.edu | Ciadvertising: Jiad: http://www.ciadvertising.org

The theory of homophily, defined by Lazarsfeld and Merton (1964), is that most human communication will occur between a source and a receiver who are alike (i.e., homophilous and have a common frame of reference). Homophily is the degree to which individuals in dyad are congruent or similar in certain attributes, such as demographic variables, beliefs and values (Touchey 1974). Gabriel Tarde (1903) also noted that social relations are generally between individuals who resemble each other in occupation and education. Hetrophily is the degree to which pairs of individuals are different in certain attributes. Thus, heterophily is the opposite of homophily.

Rogers and Bhowmik (1971) mentioned that homophily occurs frequently because communication is more effective when source and receiver are homopilous. When two individuals share common meanings, belief, and mutual understandings, communication between them is more likely to be effective. Individuals enjoy the comfort of interacting with others who are similar. Talking with those who are markedly different from us requires more effort to make communication effective. Heterophilous communication between dissimilar individuals may also cause cognitive dissonance because an individual is exposed to messages that are inconsistent with existing beliefs, resulting in an uncomfortable psychological state.

Homophily and effective communication breed one another. The more communication there is between members of a dyad, the more likely they are to become homophilous; the more homophilous two individuals are, the more likely that their communication will be effective. Individuals who depart from the homophily principle and attempt to communicate with others who are different from them often face the frustration of ineffective communication. Differences in technical competence, social status, beliefs, and language, lead to mistakes in meaning, thereby causing messages to be distorted or to go unheeded.

Homophily is the principle that contact between similar people occurs at a higher rate than among dissimilar people. The pervasive fact of homophily means that cultural, behavioral, genetic or material information that flows through networks will tend to be localized. Homophily implies that distance in terms of social characteristics translates into network distance, the number of relationships through which a piece of information must travel to connect two individuals. It also implies that any social entity that depends to a substantial degree on networks for its transmission will tend to be localized in social space, and will obey certain fundamental dynamics as it interacts with other social entities in an ecology of social forms.

2-1.Homophily: a basic or organizing principle.

A pattern as powerful and pervasive as the relationship between association and similarity did not go unnoticed in classical Western thought. In Aristotle's Rhetoric and Nichomachean Ethics, he noted that people "love those who are like themselves" (Aristotle 1934:1371). Plato observed in Phaedrus that "similarity begets friendship" (Plato 1968:837). The positive relationship between the similarity of two nodes in a network and the probability of a tie between them was one of the first features noted by early structural analysts (Desehields and Kara, 2000, p 316).

The classic citation in the sociological literature seems to be Lazarsfeld's and Merton's (1954) study of the friendship process in Hilltown and Craftown. The use of the term "homophily" coalesced the observations of the early network researchers, and linked it to classic anthropological studies of homogamy (homophily in marriage formation). The proverbial expression of homophily, "birds of a feather flock together," has been used to summarize the empirical pattern ever since.

According to Desehields and Kara (2000), "The earliest studies of homophily concentrated on small social groups, in which an ethnographic observer could easily ascertain all of the ties between members (whether those ties were behavioral, like sitting together at a cafeteria table, or reported, as when an informant tells about his or her close friends). Therefore, our first systematic evidence of homophily in informal network ties came from school children, college students and small urban neighborhoods.(p317)" The initial network studies showed substantial homophily by demographic characteristics like age, sex, race/ethnicity and education (e.g., Bott 1929, Loomis 1946), and by psychological characteristics like intelligence, attitudes, and aspirations (e.g., Almack 1922, Richardson 1940).

By mid-century a vigorous research tradition had grown, with two main themes. As issues of race and school desegregation dominated the U.S. political arena, many researchers focused on the extent of informal segregation in newly desegregated schools, buses and other public places (Desehields & Kara, 2000, p 318). While observation of relationships eventually lagged behind the study of prejudice and other attitudinal measures, researchers found strongly homophilous association patterns by race and ethnicity (although these behavioral patterns were sometimes weaker than the attitudinal prejudice). A second tradition began with the strong assumption that peer groups were an important source of influence on people's behavior (especially among adolescents). Whether the focus was positive influence or negative influence, cross-sectional association between some individual characteristic and the corresponding characteristics of that individual's friends were used as evidence for the potency of peer context (e.g., Berelson et al 1954).