The social implications of planning: How public predictions bias future plans

The planning fallacy, or tendency to underestimate how long a task will take to complete, is a robust phenomenon. Although several explanations have been offered (e.g., ignoring underestimations made in the past), we hypothesized that self-presentation concerns may also contribute to the bias, and that this effect may be exacerbated by a previous failure to complete a task on time. Half of our sample ( n = 85) were led to believe that they failed to complete an initial task on time, and half were not. Predictions were then made for time to complete a second task either verbally to a familiar experimenter (high self-presentation) or anonymously (low self-presentation). Although verbal predictions exhibited the typical planning fallacy, anonymous predictions did not. Additionally, verbal predictions were less accurate, that is, less correlated with actual completion times, than were anonymous predictions. There was no significant difference in the bias as a result of the failure manipulation, nor was there an interaction between the self-presentation and failure conditions.