The influence of social vs. non-social reward stimuli on behaviour and neural outcomes of the probabilistic reward task (PRT)

In this within-subjects study, the effects of social and non-social reward stimuli (providing feedback on some of the correct responses) on response bias and reward learning in a probabilistic reward task (PRT) will be investigated. Prior research on the role of social feedback (e.g. a smiling face or a thumbs up gesture) in the context of learning, feedback assessment and working memory has highlighted the significance of these stimuli. For example, thumbs up/down led to enhanced Feedback-Related Negativity (FRN) amplitudes (an EEG marker of early feedback processing) and better behavioral performance compared to matched non-social stimuli (Pfabigan et al., 2019). However, an online study in which large groups of participants received feedback of only one feedback type (either social or non-social) while performing a probabilistic reward task (PRT; Pizzagalli et al., 2005) did not show this processing benefit of social stimuli (Sailer, Wurm, Pfabigan, 2024). In the PRT one response option is rewarded more often than the other one, which usually leads to a behavioral preference for the more frequently rewarded response. Either the benefit of social feedback is not transferable to a different experimental task, or this benefit is only observable when performance in the social vs. non-social domain is directly compared within individuals. The current study aims to address this open question by adapting the study by Sailer et al. (2024) as a within-subjects design in which participants will be asked to perform two parallel versions of the PRT, one with social feedback and one with non-social feedback. EEG will be measured while participants perform the task to (1) complement the behavioral analyses including signal detection theory and hierarchical drift diffusion modeling on a trial-by-trial basis on the neural level (e.g., Nunez, et al., 2017), and (2) to assess the neural processing of the feedback stimuli based on the event-related (FRN/RewP component) and non-phase locked activity (frontal midline theta activity) in the EEG (Cohen et al., 2017). After finishing the two PRT versions (lasting approximately 30-35 min), participants will be administered the Door task using thumbs up/down as feedback stimuli (approximately 6 min) - to assess independent EEG data on reward processing. Before the EEG data collection several questionnaires will be filled in. Based on previous research, we hypothesize that social reward feedback will enhance the response bias and modulate ERP components more strongly than the non-social reward feedback.