The Eyes as a Mirror of the Unconscious: What Pupil Dilation Reveals About Unconscious Analytic Thought in Insight Problem Solving.

Recent studies suggest forms of unconscious processing in classical insight problem solving. In particular, the unconscious analytic thought (UAT) approach speculates that the creative act of restructuring such very demanding problems implies a form of high-level unconscious thought, mainly active during incubation. The present study aims to investigate whether pupillary dilation, typically associated with conscious cognitive effort, can also represent an indicator of unconscious cognitive effort (UAT). In the experimental condition, participants attempted to solve the problem and, during the incubation phase, performed a series of single-digit arithmetic calculations. In the control condition, participants only performed the arithmetic calculations. Results showed a significant interaction between group (solvers, non-solvers and control) and temporal course on pupillary dilation. In particular, solvers, conversely to the other two groups, showed high and constant pupillary dilation during all the incubation phase, suggesting the maintenance of constant cognitive effort at an unconscious layer not attributable to anything other than the processing of the insight problem solution. In the other two groups, instead, the pupil size-starting at the same level as solvers-progressively decreased during the execution of the arithmetic task. Our results are discussed in the light of the debate on dual process theories.