Incubation process during problem solving

It is a popular belief that setting a difficult problem aside can lead to a solution idea occurring either spontaneously or on return to the task. Researchers in problem solving have labelled breaks during solution attempts as "Incubation" periods. A volume of positive laboratory findings support the reality of the phenomenon. However, the question of how incubation works still remains open. The two main current alternatives which were addressed by the present project were (a) that there is active unconscious work on the task during the incubation period and (b) that nothing happens during incubation except that attention is withdrawn from the difficult problem, so that on returning there is a chance for a new start. Previous studies have found support for both the unconscious work and the attention withdrawal explanations. However, the conflicting studies have differed in the nature of the problems used (single solution insight tasks v. multisolution or "divergent" tasks) and in when the incubation period was allowed (immediately after task was explained v. after a period of work). The present project used both types of tasks and examined whether type of task and placement of incubation period explain the previous discrepant results.



Three experiments were carried out. Experiment 1 involved a divergent thinking task (Think of as many new uses for a brick as you can.) and delayed incubation with both spatial and verbal interpolated tasks. Experiment 2 involved a spatial insight problem with immediate incubation using spatial and verbal tasks. Experiment 3 used a verbal insight problem, delayed incubation and spatial and verbal interpolated tasks. In all cases, incubation periods were varied (long v. short).







The studies also examined possible effects of the similarities between the target problem solving tasks and the interpolated activities during the incubation periods. Previous studies had used target and interpolated tasks during incubation periods that differed in their spatial or verbal character from each other. The present project included target and interpolated tasks which were similar or different to each other in terms of whether they were predominantly verbal or spatial. The effects of the similarity or otherwise between target and interpolated incubation tasks were predicted to be different by explanations based on unconscious work as against attentional switching and forgetting. Finally, our methods included checks for possible conscious work during the supposed incubation period by testing suitable control groups on the interpolated tasks alone without any interrupted task.



Results supported a role for unconscious work during incubation, after a conscious work period, in the divergent thinking task since post-incubation performance was better with longer periods of mental rotation during incubation; less improvement was evident with a verbal incubation task. With single solution insight tasks weak or no effects were found for incubation immediately following task presentation. It is possible that powerful sets were established as the task instructions were processed and could not be weakened by the relatively short incubation periods employed here.