The interplay between verbal and visual information: how repetition and photos influence belief

Repetition increases belief for both true and false statements. This illusory truth effect is pervasive, occurring for general facts (e.g., trivia), political news headlines, and health related claims. The effect is often attributed to the fluency account, in which repetition increases processing fluency, and this ease of processing is used as a cue for truth. Photos can also influence belief through a similar underlying mechanism. Presenting statements with semantically related and unrelated photos increases and decreases belief, respectively. The primary goal of the current study is to investigate whether the two effects interact. That is, does the addition of related and unrelated photos amplify or reduce the effect of repetition on perceived truth, respectively. In Experiment 1, participants (N = 151) rated the truth of trivia statements across three photo conditions (related, unrelated, none). In Experiment 2, participants (N = 201) rated the truth of political headlines across two photo conditions (related, none). In Experiment 3, participants (total N = 604) rated the truth of trivia statements across two photo conditions (related, none) and two stimulus sets, either with or without repetition. Overall, repetition increased belief, the photos did not influence belief, and there was not an interaction effect. The results suggest that when two different factors operating under a similar mechanism are at play in belief formation, the dominant effect (e.g., repetition) may overshadow the weaker effect (e.g., presence of photo). Even without the masking effect of repetition, we find that the effect of photos on belief is weak.