What psychological pressure entails the feeling that one must do something because others are doing it?

The correct choice, peer pressure, specifically refers to the psychological pressure individuals feel to conform to the behaviors, attitudes, or actions of their peers. This can manifest in various ways, such as wanting to fit in, gain acceptance, or avoid social ostracism. Peer pressure can encourage individuals, especially adolescents, to engage in activities they might not normally consider, often driven by the desire to align with the group.

Although other concepts like groupthink, conformity, and social influence are related to group behavior and societal norms, they have distinct meanings. Groupthink involves a group's desire for harmony or conformity leading to irrational or dysfunctional decision-making. Conformity refers more broadly to any change in behavior or belief as a result of real or imagined group pressure. Social influence encompasses a wider range of influences on attitudes and behaviors, including authority, persuasion, and social norms. Peer pressure is specifically focused on the influence of peers, making it the most appropriate choice for describing the pressure to act because others are doing so.