A series of field studies focused on the role of similarity as niche construction in friendships. Using a free-range dyad harvest method, we collected 11 independent samples with 1,523 interacting pairs, and compared dyad members' personality traits, attitudes, values, recreational activities, and alcohol and drug use. Within-dyad similarity was statistically significant on 86% of variables measured. To determine whether similarity was primarily attributable to niche construction (i.e., selection) or social influence, we tested whether similarity increased as closeness, intimacy, discussion, length of relationship, and importance of the attitude increased. There were no effects on similarity of closeness, relationship length, or discussion of the attitude. There were quite modest effects of intimacy, and a reliable effect of the shared importance of the attitude. Because relationship length, intimacy, closeness, and discussion can all serve as markers of opportunity for, or potency of social influence, these data are consistent with the "niche construction" account of similarity. In 2 follow-up controlled longitudinal field studies, participants interacted with people they did not know from their large lecture classes, and at a later time completed a survey of attitudes, values, and personality traits. Interacting pairs were not more similar than chance, but for the 23% of dyads that interacted beyond the first meeting, there was significant similarity within dyad members. These 2 lines of inquiry converge to suggest that similarity is mainly due to niche construction, and is most important in the early stages of a relationship; its importance to further relationship development wanes. (PsycINFO Database Record

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Three experiments investigate how stereotypes form as justifications for prejudice. The authors created novel content-free prejudices toward unfamiliar social groups using either subliminal (Experiment 1, N = 79) or supraliminal (Experiment 2, N = 105; Experiment 3, N = 130) affective conditioning and measured the consequent endorsement of stereotypes about the groups. Following the stereotype content model, analyses focused on the extent to which stereotypes connoted warmth or competence. Results from all three experiments revealed effects on the warmth dimension but not on the competence dimension: Groups associated with negative affect were stereotyped as comparatively cold (but not comparatively incompetent). These results provide the first evidence that-in the absence of information, interaction, or history of behavioral discrimination-stereotypes develop to justify prejudice.

Articulate reasons are cogent for us only when our inarticulate feelings of reality have already been impressed in favor of the same conclusion.

Social ecologies shape the way people initiate and maintain social relationships. Settings with much opportunity will lead to more fine-grained similarity among friends; less opportunity leads to less similarity. We compare two ecological contexts-a large, relatively diverse state university versus smaller colleges in the same state-to test the hypothesis that a larger pool of available friendship choices will lead to greater similarity within dyads. Participants in the large campus sample reported substantially more perceived ability to move in and out of relationships compared to participants in the small colleges sample. Dyads were significantly more similar on attitudes, beliefs, and health behaviors in the large campus than in the small colleges sample. Our findings reveal an irony-greater human diversity within an environment leads to less personal diversity within dyads. Local social ecologies create their own "cultures" that affect how human relationships are formed.