The influence of inner speech suppression on the insight problem solving

OBJECTIVE: Inner speech suppression hinders solution of verbal but enhances solution of visual insight problems. We aimed to find out whether it hinders the solution of matchstick problems. Participant's eye movements were analyzed to examine in detail possible effects on solution process characteristics proposed by the Representational change theory (RCT) - initial representation of the problem, impasse, and restructuration. DESIGN: 60 participants were randomly assigned to either experimental or control group. Both groups were solving two matchstick problems of different difficulty in random order. Inner speech restriction in experimental group was induced by concurrent listening to repetitive series of changing letters. Eye movements were recorded via eye tracker. RESULTS: In line with the RCT, we found significant difference between solution times for easier and harder problem. Listening to irrelevant speech did not affect solution rates or times. Considering eye movements, only participant's initial representation of the problems corresponded to the RCT. No effects of inner speech suppression on examined eye movement patterns were observed. CONCLUSIONS: Our study extends knowledge about the role of inner speech in problem solving to previously unexamined task. Results suggest that matchstick problems are partially solved by different processes than either verbal or classic visual insight problems, since their solution is unaffected by inner speech suppression. Inclusion of eyetracking methods in future research examining effect of inner speech on problem solving could provide more nuanced picture of its functions.