How verbal-nonverbal consistency shapes the truth

Abstract The experience of fluency, or subjective ease, has a robust effect on human judgment, including the extent to which a fluently processed stimulus is perceived as true, familiar, or attractive. Evidence that fluently processed messages are perceived as true has primarily focused on written text or object images while much of human communication occurs when people can both see and hear each other. As such, little is known about the characteristics of communication that lead to an emergent sense of fluency in an interpersonal context. We propose that the consistency of a senders' verbal and nonverbal behavior, or communicative coherence, facilitates the integration of information across communicative modalities and thus the fluency of speech comprehension. By this mechanism, we expect communicative coherence to shape perceptions of truth. Consistent with our hypotheses, we find that senders' verbal-nonverbal consistency increased perceivers' comprehension fluency, leading them to accept the sender's message as true (Study 1). Further, we use an audio-video off-set procedure to manipulate communicative coherence, and find that audio-video offset caused perceivers to doubt the truthfulness of a message (Study 2). That is, senders' communicative coherence appears to cause perceivers to evaluate messages as truthful. Findings extend a rich literature on the effects of processing fluency by pointing toward the importance of understanding the antecedents of processing fluency in interpersonal contexts typical to human history.