Mental set is the tendency to solve novel problems by applying the same procedure based on previous experience with problems of the same type even when a simpler procedure or a more efficient solution can be found. The aim of the study was to investigate the differences in perceived task difficulty depending on the given solution. We expected judgments of difficulty to reflect the implicit detection of the conflict between set and simpler solutions. We used the classical paradigm with water jar problems (Luchins, 1942). In the experimental group (N=38) participants solved a total of 15 problems as follows: ten set problems solvable by using a multi-step strategy, two critical problems solvable either by the multi-step strategy, or by a much simpler, single-step strategy, one extinction problem solvable only by the single-step strategy, and finally another two critical problems. The procedure for the control group (N=40) included only five final problems. After each solution, participants were asked to make a judgment of difficulty. In the experimental group, the results showed that the task was perceived as more difficult when participants gave a multi-step solution for the first critical problem in comparison with giving a simpler single-step solution. Furthermore, we analysed judgments in the critical problem occurring after the extinction problem, depending on solutions given for one critical problem preceding and the other following the extinction problem. The results showed that participants who solved both critical problems with multi-step strategies assessed problems to be more difficult in comparison with participants who applied simpler single-step strategies only after the extinction problem or with participants who gave simpler solutions to both critical problems. In the control group there were no differences in judgments of difficulty depending on given solutions. The results suggest that participants were sensitive to the conflict when giving the solution arising from their mental set. |