Distortions in reports of health behaviors: The time span effect and illusory superiority

The occurrence of a time span effect and illusory superiority in self reports of health behaviors was tested. It was found that people report proportionally lower frequencies of both healthy and unhealthy behaviors if they give frequency estimations over a longer as compared to a shorter time span (time span effect). In addition, they report lower frequencies of unhealthy behaviors, and higher frequencies of healthy behaviors for themselves than for the average other (illusory superiority). For healthy but not for unhealthy behaviors a stronger illusory superiority effect was obtained in frequency reports for behavioral expectations as compared to past behaviors. Potential explanations and implications for subjective measurements of health behavior are discussed.