Abstract
<p>Previous research has reported a processing advantage for social over non-social stimuli when using culturally overlearned social gestures such as thumbs up/down as feedback stimuli. However, these stimuli confounded sociality with a known communicative meaning and its inherent familiarity, hence it is not clear whether the processing advantage arose from the social nature or the communicative meaning of the stimuli or a combination of both. This pre-registered EEG study aimed to disentangle these two characteristics and investigated whether a processing advantage is also observable for social gestures without previously known communicative meaning. Forty-two healthy volunteers (31 women) conducted a time estimation task and received feedback via social-unfamiliar (unknown hand gestures) and nonsocial-unfamiliar (abstract shapes) stimuli, as well as social-familiar stimuli (thumbs up/down) while EEG was recorded. Single-trial Feedback-Related Negativity (FRN) and P300 amplitudes and frontal midline theta (FMΘ) power were extracted to assess early feedback evaluation, cognitive control, and more elaborate processing stages such as working memory updating.Task performance did not differ between social-unfamiliar and nonsocial-unfamiliar stimuli, but was slightly better for social-familiar stimuli. The FRN differentiating between positive and negative feedback was largest for nonsocial-unfamiliar stimuli, while comparable for both social conditions. In contrast, FMΘ power differentiated between positive and negative feedback only for social-familiar stimuli. For P300 amplitudes, the difference between negative and positive feedback was more pronounced for social-unfamiliar than social-familiar feedback, which was mostly driven by smallest P300 amplitudes after negative social-unfamiliar feedback.The current results speak against a processing advantage purely driven by the social nature of the stimuli. It seems to be the combined effect of well-known communicative meaning and social stimulus characteristics that leads to the previously proposed processing advantage observed on the behavioral and neural level.</p>