The bystander effect is a phenomenon in which individuals are less likely to help in an emergency situation when other people are present. This effect occurs because people tend to assume that someone else will intervene, or they may feel less responsibility in a group. The more people present, the less likely any one person is to help.
- People conform to group norms under social pressure (B) refers to social conformity, which is different from the bystander effect.
- Individuals mimic the behavior of others in ambiguous situations (C) refers to social imitation or the concept of social proof, not the bystander effect.
- Social loafing increases in larger groups (D) refers to the tendency of individuals to exert less effort in a group setting, but it is a different phenomenon from the bystander effect.
Thus, the correct answer is (A), where people tend to help more when they are alone than when others are present.