An EEG-study on the extent to which partisanship conditions the processing of politicians’ faces

Partisanship has been associated with various cognitive biases. These findings are primarily based on self-reports and task performance and less on measures of neural activity. We build on the related literature on in-group/out-group dynamics that employs a face-viewing paradigm and electroencephalography methods to analyze biases. Reviewing this literature, we developed and preregistered several hypotheses about the extent to which partisanship is associated with neural processing of political faces. Our lab experiment was conducted in the Netherlands (N=51) and sufficiently-powered to pick up modest effect sizes for in-party/out-party comparisons. As preregistered, we find that faces of political leaders elicit a stronger N170 ERP response than faces of strangers, but we did not find the same pattern for the N250 component. Also contrary to our preregistered hypotheses, we find no statistically significant differences in the P200 and N200 components between in-party and out-party leader faces. The strength of partisanship also did not correlate with P200 or N200. We discuss whether different interpretations of these signals (e.g. familiarity or affective processing) guide our theories about how partisan bias emerges and operates.