Mice-side bias: Deliberative decision making in a model of rule revision reveals 'myside' confirmation bias-like cognitive processes in mice.

Confirmation or myside bias--over-valuation of novel information which confirms previously internalized cognitive content (prior beliefs, rules of conduct, etc.) and corresponding under-valuation of disconfirming novel information--constitutes a serious obstacle to adaptive revision of our beliefs, especially in ambiguous or complex epistemic environments. Indeed, myside bias has become a particularly pernicious fact of societal cohesion, contributing to the propagation of fake news, to social polarization, and even to the replication crisis in experimental science. By contrast, relatively little is understood about either its neurocognitive underpinnings or its evolution, one reason for this being that the potential presence of myside bias-like tendencies in non-human animals has never been directly tested. Hence, in order to advance research in both of these directions, we designed a novel mouse model of everyday-like rule revision such that the dynamic model environment would be sufficient to call out myside bias-like behaviors providing that mice did indeed possess the particular kind of competing neurocognitive processes necessary for it to manifest. Here, we both validate that model and provide the first behavioral descriptions of myside confirmation bias-like deliberative profiles in a non-human animal. Notably, we observe that this bias does not manifest in a merely unreflective or heuristic/ system 1 manner but rather also emerges through and indeed increases deliberative behaviors, especially in contexts of low representational resolution. Several other parallels with findings from human studies of myside bias are also detailed in the discussion.