Individual differences in working memory capacity predict the behavioral effects of induced eye movements in persuasion.

OBJECTIVES: To study the role of the working memory (WM) in persuasion, eye movements (EMi) were induced during the processing of auditory persuasive information. EMi tax the WM and may thereby prevent defensive self-regulation. However, these effects may depend on individual differences in WM capacity. METHOD: In an online experiment in Germany, WM capacity was assessed at pretest with the Forward and the Backward digit span, after which participants (N = 230) were all exposed to an auditory persuasive message on fruit and vegetable consumption. Half of them were asked to follow with their eyes a neutral, horizontally regular moving stimulus on a screen (EMi condition). The dependent variable was self-reported fruit and vegetable consumption assessed after two weeks. RESULTS: Tested in a single statistical model (controlling for each other), both WM capacity measures significantly moderated the effects of EMi on self-reported behavior (Forward p = .004, η2 = 0.037; Backward p = .002, η2 = 0.042), but when tested separately the interactions were no longer significant (Forward p = .14, η2 = 0.01; Backward p = .077, η2 = 0.012). Combining both measures in one difference score revealed significant moderation (p < .001, η2 = 0.055): relatively higher Forward scores made EMi lead to more self-reported behavior (p = .001, η2 = 0.046). CONCLUSIONS: Individual differences as well as induced difference in available WM capacity are related to the persuasive process. The combination of the two aspects of WM capacity, the simple rehearsal (Forward span) as well as the manipulation of information (Backward span), influenced the persuasion process.