Encountering a newcomer attenuates shared evaluative standards: experimental evidence of rapid emergence and partial persistence

Collective activity requires individuals to converge on common yardsticks for judging the world; however, it remains unclear how these evaluative standards (ES) respond when a group encounters unfamiliar members. Using a newly developed dot-estimation task informed by Sherif’s classic norm-formation studies, this study experimentally tracked (a) how shared ES emerge through dyadic interactions and (b) how they respond to a newcomer whose judgements systematically diverge. Participants first completed rounds with a partner whose estimates gradually aligned with their own, with perceptual bias shifting reliably toward that partner’s standard within a single block of thirty trials. However, when a newcomer with divergent estimates entered, participants partially shifted toward the newcomer’s standard, while their responses suggested carryover from the prior interaction. Impressions of the divergent newcomer did not depend on whether participants had previously established a shared standard with another partner, indicating that brief behavioural alignment does not by itself generate derogation of a divergent other. Taken together, these findings show that shared ES form quickly through dyadic interaction and, although attenuated by exposure to a newcomer, persist in part within individuals. Understanding the micro-dynamics of their formation and partial persistence helps explain how groups negotiate common standards and how those standards may attenuate—without fully unravelling—when group composition changes.