Final answer:
Darley and Latane's (1968) theory suggests the bystander effect, where people in a group are less likely to help someone in distress due to diffusion of responsibility.
Step-by-step explanation:
Darley and Latane's (1968) theory suggests that the bystander effect: individuals are less likely to offer help to a person in need when they are in a group, as opposed to when they are alone. This phenomenon is attributed to the diffusion of responsibility, where each individual feels that someone else in the group will take action, thus reducing the pressure on themselves to intervene. The theory was developed following the tragic case of Kitty Genovese, whose murder in 1964 highlighted the potential inactivity of bystanders during an emergency when many witnesses are present.