Social and non-social feedback stimuli lead to comparable levels of reward learning and reward responsiveness in an online probabilistic reward task

Social stimuli seem to be processed more easily and efficiently than non-social stimuli. The current study tested whether such a processing advantage increases reward preferences in a probabilistic reward task (PRT), in which one response option is usually rewarded more often than the other via presentation of non-social reward stimuli. In a pre-registered online study, 75 participants were presented with a non-social reward stimulus (a star) and information about gains, which is typically used in published PRT studies. Three other groups (with 73-82 participants each) were presented with one of three social reward stimuli: verbal praise, an attractive happy face, or thumbs up. All PRT variants yielded the expected behavioural preference for the more frequently rewarded response option, both in terms of classical signal-detection-theory analysis as well as in terms of drift diffusion modelling analysis. There was no processing advantage of social over non-social reward stimuli. Bayesian analyses further supported the observation that social reward stimuli did neither increase nor decrease behavioural preferences in the PRT. The current findings suggest that the PRT is a robust experimental paradigm independent of the applied reward stimuli.