Examining Ingroup Persuasion and Expectancy Violation as Competing Mechanisms for Biased Information Processing in Social Media

This web-based experiment (N = 447) tested competing theoretical perspectives—Expectancy Violation Theory and ingroup persuasion—on how individuals process online information about a politicized issue. Republican and Democratic participants read pro- or anti-mask comments from Democrat, Republican, or unknown sources. Results partially supported the EVT perspective: Republicans were more persuaded by attitude-consistent anti-mask comments when they came from an unexpected source (a Democrat) rather than an expected one (a Republican). No evidence supported ingroup persuasion. Further analyses revealed that this expectancy-violation effect was contingent on recipients’ pre-existing attitudes, suggesting that unexpected sources exert influence primarily when message positions align with recipients’ prior beliefs. Message evaluation served as a key psychological mechanism underlying this effect, mediating the influence of unexpected sources on attitude. Findings offer theoretical insight into how expectancy violations may override identity cues in polarized online environments while still operating within the constraints of confirmation bias. The study contributes to research on biased information processing by clarifying when source-based expectancy violations enhance persuasion in social media contexts. © 2025 Broadcast Education Association.