Dressing-up disinformation: the contextual presentation of lies

This paper focuses on a historically documented tactic that deceivers rely on: presenting inaccurate propositions together with accurate ones. Historical sources often point to this as a textbook-method to make inaccurate claims look more believable, but there has been no experimental research on its effectiveness and background psychological processes. In three pre-registered online experiments (N = 817), we found evidence for the existence of the dressing-up effect: the mere presence of accurate information accompanying a target implausible claim on the same topic makes it more believable. The effect was not sensitive to the length of the message or the order in which accurate and inaccurate claims were presented, but it disappeared when the accurate dressing claims and the inaccurate target claim were communicated by different sources. Importantly, the effect persisted even when the participants’ accuracy motives were stimulated using a monetary reward. We tested rational models that integrate the need to update beliefs both about what is communicated, given that it has been communicated, and about the trustworthiness of the source, given what they communicated. We observe that these models do predict dressing-up effects, especially when the audience is initially uncertain about the trustworthiness of the source. We conclude that people who are epistemically vigilant can nonetheless fall for the dressing-up tactic. What is needed to counter it, is more independent information about the trustworthiness of the source.