When expertise backfires: Contrast and assimilation effects in persuasion

It was proposed that source cues bias message processing in a direction opposite to cue valence if message content violates cue‐based expectancies (contrast hypothesis), but consistent with cue valence if message content is ambiguous (bias hypothesis). In line with these hypotheses, students (N = 123) reported less favourable thoughts and attitudes after reading weak arguments presented by a high (vs. low) expertise source (Expts 1 and 2), and reported more favourable thoughts after reading strong arguments presented by a low (vs. high) expertise source (Expt 2). Conversely, students' thoughts and attitudes were more (less) favourable when a high (low) expertise source presented ambiguous arguments (Expt 2). Results are discussed in relation to dual‐ vs. single‐process accounts of persuasion and models of assimilation and contrast in social judgment.