Today’s post comes from Ben Tappin, PhD candidate in the Morality and Beliefs Lab at Royal Holloway, University of London, and Stephen Gadsby, PhD Candidate in the Philosophy and Cognition Lab, Monash University, who discuss their paper recently published in Consciousness and Cognition, “Biased belief in the Bayesian brain: A deeper look at the evidence”.
Last year Dan Williams published a critique of recently popular hierarchical Bayesian models of delusion, which generated much debate on the pages of Imperfect Cognitions. In a recent article, we examined a particular aspect of Williams’ critique. Specifically, his argument that one cannot explain delusional beliefs as departures from approximate Bayesian inference, because belief formation in the neurotypical (healthy) mind is not Bayesian.
We are sympathetic to this critique. However, in our article we argue that canonical evidence of the phenomena discussed by Williams—in particular, evidence of the backfire effect, confirmation bias and motivated reasoning—does not convincingly demonstrate that neurotypical belief formation is not Bayesian.
The backfire effect describes the phenomenon where people become more confident in a belief after receiving information that contradicts that belief. As pointed out by Williams, this phenomenon is problematic for Bayesian models of belief formation insofar as new information should cause Bayesians to go towards the information in their belief updating, never away from it. (As an aside, this expectation is incorrect, e.g., see here or here).
We reviewed numerous recent studies where conditions for backfire were favourable (according to its theoretical basis), and found that observations of backfire were the rare exception—not the rule. Indeed, the results of these studies showed that by-and-large people updated their beliefs towards the new information, even if it was contrary to their prior beliefs and in a highly emotive domain.