Pupillary change on a cognitive effort task in schizophrenia: Associations with cognition and motivation

Motivational negative symptoms in schizophrenia are associated with abnormalities in effort allocation. Pupillary dilation is a reliable biomarker of effort allocation and was used in this study to evaluate the associations between cognitive effort, ability, and motivation. Individuals with schizophrenia/schizoaffective disorder and moderate-to-high negative symptoms were assessed with pupillometry while performing a cognitive effort task that manipulated level of cognitive difficulty. Participants were also assessed with measures of ability (i.e., cognition and functional capacity), and motivation (i.e., defeatist beliefs and motivational negative symptoms). Pupillary change was examined as an effort modulation index in relation to the ability and motivation measures. Greater pupillary change (i.e., exerting greater amounts of effort) on the hard versus easy conditions was correlated with better cognition and functional capacity and lower motivational negative symptoms, while defeatist beliefs were not significantly correlated. In hierarchical regression analyses, ability measures were entered first and motivation measures were entered second. Motivation measures predicted variance beyond ability. Our findings indicate that both ability and motivation are significant determinants of pupillary indicators of cognitive effort exertion. Further, the results highlight the importance of controlling for cognition when using pupil dilation to index effort/motivation.