The reduction in personal identity and erosion of the sense of personal responsibility when one is part of a group is known as

A) social contagion.
B) the self-serving bias.
C) the false consensus effect.
D) deindividuation.

Deindividuation is the phenomenon where people lose their sense of personal identity and responsibility when they become part of a group. This can lead to a decrease in inhibitions and an increase in impulsive behavior, as people feel more anonymous and less accountable for their actions. Social contagion refers to the spread of behaviors or emotions within a group, while the self-serving bias and false consensus effect both involve individual cognitive biases rather than group dynamics.