Previous studies have suggested that, implicit information processing plays important roles in insight problem solving. However, some studies reported that, when subliminal hint information was presented in a sequential order, performance did not improve. The results might suggest that subliminally presented information was stored in a rather static way, and could not be integrated with succeeding subliminal information. In order to examine whether subliminal information presented sequentially can be integrated to control solution strategies, we employed, as a method of presenting subliminal hint, the Illusory Line Motion (ILM), where presentation of a dot followed by a line produces illusory extension of the line. In Experiment 1, we presented three lines with dots using ILM to examine if it could produce better performance in the nine dots problem. Although there was no increase in the solution rate, more subjects in the experimental condition drew lines in accord with the order of hints. Experiment 2 suggested that the results obtained by Experiment 1 could not be attributed to presentation of dots outside the square frame formed by nine dots. These results suggest that sequentially presented subliminal information could be integrated and used jointly in later problem solving.
