Einstellung defused: Interactivity and mental set.

Mental set is observed when a familiar problem-solving strategy is applied to new problems that can be solved in simpler, more efficient ways. It is most famously illustrated in the water jar problems (Luchins, 1942 ). In these volume measurement problems, participants learn a rule to obtain an exact volume of liquid involving a complex combination of liquid transfer. Participants persevere in using this rule for new problems that can be solved with a much simpler rule. In two experiments presented here, participants completed the water jar task either in interactive conditions with actual water jars at a sink or in noninteractive conditions, with the problems presented on paper, as in the original Luchins procedure. Interactivity significantly reduced the degree of perseverance. In addition, participants' visuospatial skills significantly predicted the rate of perseverance (and the latencies to solution) in interactive but not in noninteractive conditions. These results underscore the importance of designing problem-solving experiments that engineer distributed cognitive systems in which participants coordinate internal and external resources in thinking.