Under what condition is social loafing most likely to occur?

Social loafing is a phenomenon where individuals exert less effort when working in a group compared to when they work alone. The correct answer revolves around the concept of accountability within a group setting. Social loafing is most likely to occur when group members are not individually accountable for their contributions, which typically happens in situations where their efforts cannot be directly measured or recognized.

When group members are individually accountable, each person's contribution can be evaluated, which often motivates them to work harder to meet expectations. Therefore, the lack of individual accountability can lead to a diffusion of responsibility, where members feel their individual effort is less critical to the group outcome, thus fostering social loafing.

In terms of the other options, when tasks are challenging or require high motivation, group members are more likely to engage and contribute actively. When tasks are simple, while there could be a temptation to slack off, if members know their individual input is necessary for success, they may still maintain individual accountability. Highly motivated group members are also less likely to exhibit social loafing, as their drive pushes them to contribute fully to the group's objectives.