Non-thoughtful persuasion is a matter of time: Interactions between duration of persuasion attempt and cognitive load

Previous research demonstrates that increasing exposure over time often leads to greater attitude change in favor of the target attitude. But why does this exposure duration-attitude change link occur? The present work suggests that the effects of exposure duration on attitude change are non-thoughtful and implicit in nature, and that persons who are thinking hard are less prone to the effects of exposure duration. Three studies tested this idea by manipulating the ability of persons to think effortfully by putting them under cognitive load. Study 1 demonstrated the basic duration of persuasion attempt X cognitive load interaction in a jury simulation context: Participants under no load showed no effect of increasing exposure to a persuasive message, while participants under cognitive load were more persuaded by a longer exposure duration (compared to a shorter duration). Study 2 replicated this effect in a different persuasion context (attitudes about sleep) and also added an additional qualifier: The credibility of the source. The expected time X load interaction occurred for an expert (but not a non-expert) source. Study 3 replicated this same pattern while ruling out a potential confound from Study 2 (type of instructions). Taken as a whole, these results imply that, given certain pre-conditions necessary for most persuasion to occur at all (comprehension of the argument, credibility of the source), non-thoughtful persuasion is very probable over the long term unless persons are actively resisting that persuasion.