Disentangling effects of expectancy, accuracy, and empathy on the processing of observed actions.

A number of studies suggest that event-related potential (ERP) components previously associated with error processing might represent expectation violation instead of valence. When observing others, these processes might further be modulated by trait empathy. We suggest that trait empathy modulates expectancy formation and that these expectancies then influence observed response processing as reflected in a frontocentral negative ERP component resembling the previously described observer error-related negativity. We acquired single trial ERPs of participants who observed another person in a true- or false-belief condition answering correctly or erroneously. Additionally, we prompted participants' expectancy in some trials. Using linear mixed model analyses, we found that for low empathy participants, expectations for the false-belief condition decreased throughout the experiment, so that expectations were more pronounced in participants with higher empathy toward the end of the experiment. We also found that single trial expectancy measures derived from regression models of the measured expectancies predicted the amplitude of the frontocentral negative ERP component, and that neither the addition of empathy nor accuracy or trial type (true- or false-belief) led to the explanation of significantly more variance compared with the model just containing expectancy as predictor. These results suggest that empathy modulates the processing of observed responses indirectly via its effect on expectancy of the response.