Effort-based decision making as an objective paradigm for the assessment of motivational deficits in schizophrenia

Abstract

Background: Negative symptoms and motivational deficits are prevalent features of schizophrenia, and represent robust predictors of real-world functional outcomes. The standard for assessment of these symptoms is clinical interview and severity ratings on standardized rating scales. In the present study we examined the psychometric properties of a performance-based measure of motivational deficits in patients with schizophrenia.

Methods: Ninety-seven patients with schizophrenia were included in this investigation. Patients' willingness to expend effort for reward (i.e., motivation) was evaluated using an effort-based decision making paradigm where participants chose over a series of trials whether to expend a greater amount of effort for a larger monetary reward versus less effort for a smaller reward. Effort performance was evaluated twice, separated by a two-week interval.

Results: Patients with schizophrenia opted to expend greater effort for trials with higher reward value and greater likelihood of reward receipt. Patients did not find the task overly difficult and reported being motivated to perform well, underscoring the tolerability of the task for patients. Test-retest consistency was good and there was only minimal change in scores over time. Effort performance was not related to sociodemographic or clinical variables (e.g., positive symptoms); however, deficit syndrome patients exerted effort for reward at a significantly lower rate than nondeficit patients.

Conclusions: The effort-based decision making task used in the present study represents an objective paradigm that can be used to evaluate motivational impairments in patients with schizophrenia. Such performance-based measures of motivation may also serve as viable endpoints in clinical trials.

Keywords: Amotivation; Antipsychotics; Apathy; Effort cost; Negative symptoms; Neurocognition.