In a number of studies on ingroup bias conducted between 1961 and 1970, Vaughan found that urban Maori changed from showing outgroup preference to ingroup preference. This can be attributed to:

A) a decline in the Maori population.
B) a cognitive trend.
C) social change.
D) an ambiguous experimental design.

Ingroup Bias

The tendency to favor and prioritize the interests of one's own group over those of other groups.

Urban Maori

Individuals of Maori descent who live in urban areas of New Zealand, often experiencing a different cultural identity from traditional Maori.

Social Change

Social change encompasses alterations in the social structure and cultural values of a society over time.