According to being aware of another person’s presence divides our attention between this person and a task at hand. this division of attention is arousing, which explains why people perform better on well-learned tasks in the presence of others.

Distraction-conflict theory.

Explanation:

Robert Barron´s distraction-conflict theory suggests that the mere presence of others influences the performance level of a person completing a certain task.

The surrounding distraction produces a conflict between focusing on the task at hand and paying attention to other people. That conflict boosts arousal, leading to social facilitation. 

That kind of distraction will probably be disruptive when completing a difficult task, but for well learned tasks, distractions may either upgrade or degrade the performance level.

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