When photos backfire: Truthiness and falsiness effects in comparative judgments

Claims are more likely to be judged true when presented with a related nonprobative photo (Newman et al., 2012). According to a processing fluency account, related photos facilitate processing and easy processing fosters acceptance of the claim. Alternatively, according to an illusion-of-evidence account, related photos may increase acceptance of the claim because they are treated as tentative supportive evidence. We disentangle these potential mechanisms by using comparative claims. In forming comparative judgments, people first assess attributes of the linguistic subject of comparison and subsequently compare them to attributes of the referent (Tversky, 1977). Hence, photos of the linguistic subject in a sentence should facilitate, but photos of the linguistic referent should impair, fluent processing of this sequence. In contrast, a photo of either the subject or the referent can be perceived as tentative evidence. In two experiments (total N = 1200), photos of the subject increased acceptance of comparative claims relative to a no-photo condition (a truthiness effect), but only when the subject was otherwise difficult to visualize. Photos of the referent decreased acceptance of comparative claims relative to a no-photo condition (a falsiness effect), but only when the subject of comparison was otherwise easy to visualize. All results are consistent with a context-sensitive fluency account: increases in fluency foster, and decreases in fluency impair, acceptance of a claim as true. The results provide no support for an illusion-of-evidence account.