In predictive processing accounts of the brain, priors are the expectations a system brings to incoming sensory information — probability distributions over what the world is likely to be doing, built up through experience and shaped by evolution.
They operate below conscious awareness, and they shape what we perceive before we are aware of perceiving it. Perception on this account is less a recording of the world than a prediction of it, continuously corrected by error.
Key sources: Karl Friston, ‘The free-energy principle: a unified brain theory?’, Nature Reviews Neuroscience 11 (2010); Andy Clark, ‘Whatever next? Predictive brains, situated agents, and the future of cognitive science’, Behavioral and Brain Sciences 36(3) (2013).
The cultural extension — a proposal, not an established finding
We are interested in whether priors are acquired culturally, so that people raised in similar conditions come to share them. This is an active proposal rather than a settled result, and we flag it as such.
The serious attempt to formalise it is Samuel Veissière, Axel Constant, Maxwell Ramstead, Karl Friston and Laurence Kirmayer, ‘Thinking through other minds: A variational approach to cognition and culture’, Behavioral and Brain Sciences (2020), which asks whether there is a unifying account of the mechanisms involved in the acquisition of culture and answers with a free-energy formalism covering shared habits, norms and expectations. It ran as a target article with peer commentary — meaning it is a proposal the field is still arguing about, not a conclusion the field has reached.
So: priors are a well-evidenced construct in individual cognition. The move from individual priors to shared cultural priors is the interesting claim, and the unfinished one.
Worth keeping visible: priors in this literature are formal, subpersonal and quantitative, while Habitus is dispositional, personal and socially produced. Filing them both as synonyms for deep disposition is a compression we are making on purpose, and it flattens a real difference in what kind of thing each one is.