Increased Sensitivity to Effort and Perception of Effort in People with Schizophrenia.

Abstract

Objective: Motivational deficits in schizophrenia are proposed to be attributable in part to abnormal effort-cost computations, calculations weighing the costs vs. the benefits of actions. Several reports have shown that people with schizophrenia display a reduced willingness to exert effort for monetary rewards when compared to controls. The primary goal of the current study was to further characterize reduced willingness to exert effort in schizophrenia by determining whether reduced willingness reflects (1) reduced sensitivity to reward, (2) increased sensitivity to effort, or (3) a combination of both.

Design: We assessed effort-cost decision-making in 30 controls and 30 people with schizophrenia, using 2 separate experimental tasks. Critically, one paradigm allowed for independent estimation of effects of reward and effort sensitivity on choice behavior. The other task isolated effort sensitivity by measuring effort in the absence of reward. Clinical interviews and self-report questionnaires were administered to people with schizophrenia to determine negative symptom severity.

Results: Across both tasks, we found evidence for reduced willingness to exert effort in people with schizophrenia compared to controls. Further, in both paradigms reduced willingness to exert effort was driven by increased sensitivity to effort in people with schizophrenia compared to controls. In contrast, measures of reward sensitivity did not significantly differ between groups. Surprisingly, we did not find correlations between task variables and measures of negative symptom severity.

Conclusions and relevance: These findings further specify prior work by identifying a specific contributory role for increased effort sensitivity in effort-cost decision-making deficits in schizophrenia.