The contact-prejudice effect may be partly an artifact of publication bias.

Evidence

Contradicting these results in part is an analysis that uses Vevea and Hedges’s (1995) general linear model approach. Vevea kindly conducted this analysis for us and found that the sample file was missing numerous small studies with small effects. After adjustment for these cases, his method did not find a significant overall relationship between contact and prejudice (Z .02, ns). However, for those 118 samples with between-groups designs and strong controls, the adjusted effect size did reach statistical significance (mean Z .109, one-tailed, p .02). — Thomas F. Pettigrew, Linda R. Tropp, A Meta-Analytic Test of Intergroup…, 108

Categorization

• QUESTION: This suggests the canonical contact hypothesis effect might shrink considerably after correcting for missing small studies; worth chasing the original Vevea and Hedges meta-analytic adjustment method.
• XREF: Connects to broader debates on publication bias in social psychology, especially post-replication-crisis reassessments of classic effects like Milgram, ego depletion, and stereotype priming. — connects to: Meta-analyses overestimate effect sizes because null results go unpublished. — Thomas F. Pettigrew, Linda R. Tropp, A Meta-Analytic Test of Intergroup…, 44; Trim-and-fill and funnel graph methods tend to overestimate publication bias. — Thomas F. Pettigrew, Linda R. Tropp, A Meta-Analytic Test of Intergroup…, 48; Contact’s prejudice-reducing effect is causal, not a selection or publication artifact. — Thomas F. Pettigrew, Linda R. Tropp, A Meta-Analytic Test of Intergroup…, 216

Related

• Contact’s prejudice-reducing effect is causal, not a selection or publication artifact. (similarity 0.89)
• More rigorous contact studies show larger prejudice-reduction effects. (similarity 0.88)
• Comparing published and unpublished studies tests whether reporting bias inflates effects. (similarity 0.87)
• The intergroup contact-prejudice link survives file-drawer checks, indicating limited publication bias. (similarity 0.87)
• Stronger contact effects in rigorous studies would confirm the contact-prejudice link. (similarity 0.87)
• Randomized contact experiments yield near-large prejudice reduction effects. (similarity 0.86)
• Intergroup contact reduces prejudice even beyond the groups involved. (similarity 0.85)
• The contact-prejudice effect varies across samples by design and context (similarity 0.85)
• Meta-analyses overestimate effect sizes because null results go unpublished. (similarity 0.84)
• Contact studies with cleaner control groups show larger effects. (similarity 0.84)
• Contact effects persist beyond the immediate contact situation. (similarity 0.84)
• No meta-analysis of intergroup contact research existed before this study. (similarity 0.83)
• The trim-and-fill adjustment increases the contact-prejudice effect estimate, supporting its robustness. (similarity 0.82)
• Affective factors, not knowledge gain, drive contact’s prejudice-reducing effect (similarity 0.82)
• Meta-analysis pools all studies to estimate effect sizes and moderators (similarity 0.82)