Growing evidence has suggested interesting dissociations between conscious and sub-
conscious processing in insight problem solving. It indicates a possibility that the
process of insight problem solving is largely governed by an implicit learning mecha-
nism that detects the differences between current and goal states, and regulates the
strengths of the responsible operators. If the implicit learning mechanism takes part
in the insight problem solving process, the process might be affected by a hint stimu-
lus subliminally presented, because such a stimulus could not be used by the explicit
learning system. We examined this possibility using the continuos flash suppression
technique. The results of two experiments showed that subjects subliminally presented
with the goal state of a difficult insight puzzle solved it much faster than those in the
control group. These results were discussed in terms of unconscious nature of insight
problem solving, gradual tuning of operator strengths during the impasse, and roles of
subliminal hint information in the problem solving processes.