Measuring Social Motivation Using Signal Detection and Reward Responsiveness

Abstract

Background: Recent trends in psychiatry have emphasized the need for a shift from categorical to dimensional approaches. Of critical importance to this transformation is the availability of tools to objectively quantify behaviors dimensionally. The present study focuses on social motivation, a dimension of behavior that is central to a range of psychiatric conditions but for which a particularly small number of assays currently exist.

Methods: In Study 1 (N = 48), healthy adults completed a monetary reward task and a social reward task, followed by completion of the Chapman Physical and Social Anhedonia Scales. In Study 2 (N = 26), an independent sample was recruited to assess the robustness of Study 1's findings.

Results: The reward tasks were analyzed using signal detection theory to quantify how much reward cues bias participants' responses. In both Study 1 and Study 2, social anhedonia scores were negatively correlated with change in response bias in the social reward task but not in the monetary reward task. A median split on social anhedonia scores confirmed that participants with high social anhedonia showed less change in response bias in the social reward task compared to participants with low social anhedonia.

Conclusions: This study confirms that social anhedonia selectively affects how much an individual changes their behavior based on the presence of socially rewarding cues and establishes a tool to quantify social reward responsiveness dimensionally.

Conflict of interest statement

RTS has received speaking fees from Shire Pharmaceuticals, and consulting fees from Seaside Therapeutics and Roche Pharmaceuticals. None of these activities overlap with the study described in this paper.

Figures

Fig 1. Schematic representation of the tasks.

A fixation cross appears for 500ms, followed by an empty circle. A short or a long line is then flashed inside the circle for 100ms. Participants have an infinite amount of time to respond before they receive a reward for some of their correct responses.

Fig 2. Performance in the social reward task.

Accuracy rates (A) and reaction times (B) during the social reward task. Results are split by block (1, 2, 3) and stimulus type (lean in blue, rich in red).

Fig 3. Response bias in the social reward task.

Evolution of the response bias across blocks in the social reward task (A) and correlation between change in response bias (i.e. Logb Block 3 –Logb Block 1) and social anhedonia score, R2 = .116.

Fig 4. Performance in the monetary reward task.

Accuracy rates (A) and reaction times (B) during the monetary reward task. Results are split by block (1, 2, 3) and stimulus type (lean in blue, rich in red).

Fig 5. Response bias in the monetary reward task.

Evolution of the response bias across blocks in the monetary reward task (A) and correlation between change in response bias (i.e., Logb Block 3 –Logb Block 1) and social anhedonia score, R2 = .058.