Final answer:
The individual who joined an animal rights group and subsequently adopted a vegan diet exhibited 'normative conformity' by aligning with the group norms to be accepted and to fit in.
Step-by-step explanation:
When someone joins an animal rights group and then adopts a vegan diet, the type of conformity that has occurred is normative conformity. This involves conforming to a group norm to fit in, to feel good, and to be accepted by the group. For example, in the Asch experiment, participants conformed due to normative social influence, since the line judgment task was unambiguous and participants felt the need to fit in and avoid ridicule. In contrast, informational social influence occurs when people conform because they believe the group is competent and has the correct information, particularly when the situation is unclear or the group has expertise. The student's action of adopting a vegan diet to align with the animal rights group reflects the use of a reference group to understand how to act and behave within the context of the group's values and norms.