Illusory truth effect

Biological Parallel

What you hear repeatedly probably matters, even when the source is identical—this is biology's frequency-as-truth algorithm. American crows remember threatening humans for 2.7+ years based on repeated alarm call exposure, even learning socially from groupmates who witnessed the threat. Vervet monkeys use referential alarm calls—distinct vocalizations for leopards, eagles, and snakes—where call repetition and intensity signal predator proximity and urgency. Meerkats discriminate sentinel reliability: foraging group members trust experienced sentinels who call most frequently, reducing their own vigilance when hearing from these proven sources. The pattern is consistent across unrelated lineages: processing fluency—how easily information comes to mind—serves as a validity heuristic because frequently encountered signals usually reflect real environmental regularities. The illusory truth effect exploits this same algorithm in human cognition and institutions.