What phenomenon describes how the presence of others might reduce the likelihood of an individual offering help?

The phenomenon that describes how the presence of others might reduce the likelihood of an individual offering help is known as the bystander effect. This concept illustrates that when more people are present during an emergency or a situation where help is needed, the likelihood of any one individual helping decreases. This occurs because individuals may feel less personal responsibility to act, perceiving that someone else will intervene instead.

The bystander effect is often attributed to diffusion of responsibility, where each person's sense of responsibility to take action diminishes in a group setting. Factors such as social influence and ambiguity of the situation can also play a role in this phenomenon, making it less likely for any single observer to offer assistance.

In contrast, other concepts like groupthink involve group decision-making processes that lead to poor outcomes because of a desire for harmony, cognitive load relates to the mental effort required for cognitive tasks, and actor/observer bias pertains to the tendency to attribute our own actions to situational factors while attributing others' actions to their character. Each of these terms describes different social psychological dynamics that do not specifically address the decrease in helping behavior in the presence of others.