Accuracy, error, and bias in predictions for real versus hypothetical events.

Participants made predictions about performance on tasks that they did or did not expect to complete. In three experiments, participants in task-unexpected conditions were unrealistically optimistic: They overestimated how well they would perform, often by a large margin, and their predictions were not correlated with their performance. By contrast, participants assigned to task-expected conditions made predictions that were not only less optimistic but strikingly accurate. Consistent with predictions from construal level theory, data from a fourth experiment suggest that it is the uncertainty associated with hypothetical tasks, and not a lack of cognitive processing, that frees people to make optimistic prediction errors. Unrealistic optimism, when it occurs, may be truly unrealistic; however, it may be less ubiquitous than has been previously suggested.