Social Motivation in Schizophrenia: The Impact of Oxytocin on Vigor in the Context of Social and Nonsocial Reinforcement
Experiential negative symptoms—including diminished motivation—have a profound impact on functional outcomes in schizophrenia. Animal research suggests that abnormalities in dopaminergic regulation can negatively impact effort exertion, a translational model that has been applied to individuals with schizophrenia. Paradigms that assess effort-based decision making, for example, suggest less likelihood of choosing high effort tasks that are high in probability of success, and this preference varies with negative symptoms and impaired functioning. Although asociality is another well-documented component of experiential negative symptoms, it is unclear whether diminished motivation for monetary reward extends to the social domain. To test this question, the authors designed the Social Vigor Task (SVT)—a measure of effort exertion in the context of live social encouragement. They further examined the effect of oxytocin, a neuropeptide implicated in social behavior, on vigor. Forty-two individuals with schizophrenia and 43 healthy controls completed the SVT twice: once after intranasal administration of saline placebo and again after oxytocin. Both groups showed similar increases in vigor in response to social encouragement, suggesting effort in the social context is spared in schizophrenia. Group differences in the effect of social encouragement on vigor varied by point-based reward rate and trial length. Oxytocin did not increase vigor during social encouragement in either group. Within the schizophrenia group, clinician-rated passive social withdrawal, but not active social avoidance, was negatively associated with vigor. Results suggest that people with schizophrenia show normative levels of effort in the context of social encouragement; low approach motivation, however, relates to lower effort.