In a study examining the effects of time of day on problem solving, participants solved insight and analytic problems at their optimal or non-optimal time of day. Given the presumed differences in the cognitive processes involved in solving these two types of problems, it was expected that the reduced inhibitory control associated with non-optimal times of the day would differentially impact performance on the two types of problems. In accordance with this expectation, results showed consistently greater insight problem solving performance (...) during non-optimal times of day compared to optimal times of day but no consistent time of day effects on analytic problem solving. The findings indicate that tasks involving creativity might benefit from a non-optimal time of day. (shrink)