Effort cost computation in schizophrenia: a commentary on the recent literature

Abstract

The cognitive and affective factors implicated in the motivational impairments seen in many people with schizophrenia remain poorly understood. Many research groups have done studies in the past 2 years examining the role of effort-cost computations driven by the hypothesis that overestimation of the cost of effort involved in volitional behavior might underlie the reduction in goal-directed behavior seen in some people with schizophrenia. The goal of this review is to assess the available evidence and the interpretative ambiguities that remain to be addressed by further studies. There is a clear preponderance of evidence suggesting that people with schizophrenia demonstrate altered effort allocation by failing to make high-effort response choices to maximize reward. The evidence relating altered effort allocation to the severity of negative symptoms is mixed. It remains for future work to determine the precise mechanisms implicated in altered effort allocation with two prominent possibilities: that patients 1) overestimate the cost of effort or 2) underestimate the value of potential awards. Other mechanisms that need to be investigated include the potential contributions of other impairments associated with the illness that increase the cost of effort. Furthermore, it is possible that accurate value representations fail to invigorate behavior. Although questions remain, evidence available to date suggests that the study of cost/benefit decision making may shed new light on the motivational impairments seen in many people with schizophrenia.

Keywords: Avolition; Decision making; Effort cost; Motivation; Negative symptoms; Schizophrenia.

Figure 1

Proportion of high effort choices as a function of antipsychotic-type. A. Patients on first- generation drugs show marked indifference to increasing reward levels. B. Haloperidol-equivalent dose across the patient groups. C. Patients on first-generation drugs had much higher negative symptom ratings.

Figure 2

Proportion of high effort choices as a function of negative symptoms with the patients on first- generation drugs removed from the sample. A. Probability of selecting the harder response alternative in the high and low negative symptom groups. B. The groups of high- and low-negative-symptom had very similar haloperidol equivalent doses, whereas the groups differed markedly on negative symptom severity.

Figure 3

Proportion of high effort choices in PSZ and HCs with the patients on first-generation drugs removed from the sample.