Impact of Source Credibility on Medical Information Persuasiveness: A Pilot EEG Study

This study examined behavioral and electrophysiological responses to medical sources with varying credibility levels regarding expertise and trustworthiness dimensions. We investigated how a fictional doctor's work experience (expertise), patient ratings (trustworthiness) and participants' individual characteristics influence source persuasiveness and opinion changes about true and fake medical statements. Overall, 19 participants performed a pilot study: they evaluated their agreement with medical statements, viewed information about fictional doctors with different expertise and trustworthiness levels providing a cue towards the statements, and had opportunities to revise their assessments depending on the source credibility and perceived persuasiveness. Participants also completed questionnaires on analytical thinking, need for cognition and conformity. Additionally, we employed electroencephalography (EEG) to record participants' brain responses, comparing the feedback-related negativity (FRN) response between congruent and incongruent trials based on cue consistency with participants' initial evaluations. The behavioral results suggested that patient ratings (trustworthiness) had a stronger effect on the opinion change than work experience (expertise). Higher conformity and higher cognitive reflection had a trend toward greater opinion change, while higher need for cognition correlated with less opinion change. EEG results revealed no significant amplitude difference between congruent and incongruent trials, with peaks occurring for both conditions at 200-300 ms after cue onset, alike to P300.