Affective group attachment outweighs mere categorization as a causal mediator.

Evidence

Of the social categorization and affective commitment dimensions, affective commitment appeared to be the stronger mediator of the relationship between follower perceptions of transformational leadership and satisfaction and OCB. Similarly, Ellemers et al. reported that affective commitment was the only mediator of the relationship between group structure and follower in-group favoritism. It appears that social categorization has some effects on follower perceptions, yet those effects are reduced when affective commitment was added. — Roderick M. Kramer, Geoffrey J. Leonardelli, Robert W. Livingston, Social Cognition, Social Identity, and…, 1857

Categorization

• XREF: Complicates or refines the minimal in-group bias literature (Tajfel): categorization alone may produce weaker effects than when emotional attachment to the group forms. Matters for the reader’s thread on whether mere ingroup/outgroup labels suffice to generate prejudice or whether felt belonging is required.
• corroborated: 2 independent passages support this claim — Roderick M. Kramer, Geoffrey J. Leonardelli, Robert W. Livingston, Social Cognition, Social Identity, and…, 1857