Using nonnaive participants can reduce effect sizes

J Chandler, Gabriele Paolacci, E Peer, P Mueller, KA Ratliff

Research output: Contribution to journalArticleAcademicpeer-review

106 Citations (Scopus)


Although researchers often assume their participants are naive to experimental materials, this is not always the case. We investigated how prior exposure to a task affects subsequent experimental results. Participants in this study completed the same set of 12 experimental tasks at two points in time, first as a part of the Many Labs replication project and again a few days, a week, or a month later. Effect sizes were markedly lower in the second wave than in the first. The reduction was most pronounced when participants were assigned to a different condition in the second wave. We discuss the methodological implications of these findings.
Original languageEnglish
Pages (from-to)1131-1139
Number of pages9
JournalPsychological Science
Issue number7
Publication statusPublished - 2015


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