False prophets and Cassandra's curse: The role of credibility in belief updating

Information from other sources can be beneficial or detrimental, depending on the veracity of the report. Along with prior beliefs and context, recipients have two main routes to determine veracity; the perceived credibility of the source and direct-evaluation via first-hand evidence, i.e. testing the advice against observation. Using a probabilistic learning paradigm, we look at the interplay of these two factors in the uptake (or rejection) of communicated beliefs, and the subsequent evaluation of the credibility of the communicator in light of this process. Whether the communicated belief is false (Experiment 1), or true (Experiment 2), we show that beliefs are interpreted in light of the perceived credibility of the source, such that beliefs from high trust sources are taken up (hypothesis 1), whilst beliefs from low trust sources are treated with suspicion and potentially rejected - dependent on early evidence experiences (hypothesis 2). Finally, we show that these credibility-led biased interpretations of evidence (whether belief or suspicion confirming) lead to further polarization of the perceived credibility of communicators (hypothesis 3). Crucially, this occurs irrespective of the veracity of the communication, such that sources accompanied by a high trust cue not only get away with communicating falsehoods, but see their perceived credibility increase, whilst sources accompanied by low trust cues not only have truthful communications rejected, but have their low trust penalized even further. These findings carry important implications for the consequences of artificially inflating or deflating the credibility of communicators (e.g., politicians or scientists in public debate)