Similarity of an outgroup raises bias only among highly identified ingroup members.

Evidence

In this regard, Roccas and Schwartz (1993) manipulated the degree of intergroup similarity and found that as similarity increased, high identifying group members showed an increase in intergroup bias along dimensions relevant to the ingroup. — Blake M. Riek, Eric W. Mania, and Samuel L. Gaertner, Intergroup Threat and Outgroup Attitudes, 59

Categorization

• QUESTION: Identification moderating threat reactions recurs throughout — a boundary’s constitutive role would predict this pattern, worth testing in the reader’s framework.
• XREF: connects to: Threat from similar outgroups drives more bias than threat from dissimilar ones. — Blake M. Riek, Eric W. Mania, and Samuel L. Gaertner, Intergroup Threat and Outgroup…, 59; Groups very similar to the ingroup provoke more intergroup bias than dissimilar ones do. — Blake M. Riek, Eric W. Mania, and Samuel L. Gaertner, Intergroup Threat and Outgroup…, 59

Related

• Groups very similar to the ingroup provoke more intergroup bias than dissimilar ones do. (similarity 0.93)
• Threat from similar outgroups drives more bias than threat from dissimilar ones. (similarity 0.91)
• Recategorizing outgroup members as ingroup members diminishes perceived threat. (similarity 0.88)
• Groups only compare themselves with relevant out-groups, not all available ones. (similarity 0.85)
• In-group bias intensifies against similar rather than dissimilar out-groups (similarity 0.85)
• Ingroup bias rises when outgroups are similar and ingroup identification is strong. (similarity 0.85)
• Ingroup identification strength moderates whether group-level or individual-level threats drive attitudes. (similarity 0.84)
• Cross-group friendship and empathy reduce the threat behind intergroup bias. (similarity 0.84)
• Ingroup identification causally precedes intergroup threat (similarity 0.84)
• Group-based identity forces precede realistic and symbolic threat perception (similarity 0.84)
• In-group bias arises from preferential in-group treatment rather than out-group hostility (similarity 0.83)
• Superordinate identities reduce bias and can mitigate perceived threat between groups. (similarity 0.83)
• Intergroup threat and negative outgroup attitudes relate bidirectionally, not one-way. (similarity 0.83)
• A shared superordinate identity can backfire by fueling subgroup in-group projection. (similarity 0.83)
• Threats can increase ingroup identification, not merely follow from it (similarity 0.83)