The dynamic constraint relaxation theory predicts crucial roles of the initial diversity and evaluation in creative problem-solving. We reported the experimental evidence supporting these predictions, using an insight problem. The experiments showed that the degrees of making different types of trials and the appropriate evaluation were closely related to individual differences in insight problem-solving, and that evaluation became more appropriate by making the problem-solving goal explicit. The review of the research in related fields showed that these experimental findings were in (...) congruent with the evidence obtained from different types of creative activities. (shrink)