# Updating: Learning versus supposing

- Jiaying Zhao,
*Princeton University*
- Vincenzo Crupi,
*University of Turin*
- Katya Tentori,
*University of Trento*
- Branden Fitelson,
*Rutgers University*
- Daniel Osherson,
*Princeton University*

## Abstract

Bayesian orthodoxy posits a tight relationship between conditional
probability and updating. Namely, the probability of an event A after learning an
event B should equal the conditional probability of A given B prior to learning
B. We examine whether ordinary judgment conforms to the orthodox view. In three
experiments we found substantial differences between the conditional probability
of an event A supposing an event B compared to the probability of A after having
learned B. Specifically, supposing B appears to have less impact on the
credibility of A than learning that B is true. Thus, Bayesian updating seems not
to describe the relation between the probability distribution that arises from
learning an event B compared to merely supposing it.

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