# A test of two models of probability judgment: quantum versus noisy probability

- Fintan Costello,
*University College Dublin*
- Paul Watts,
*National University of Ireland Maynooth*

## Abstract

We test contrasting predictions of two recent models of
probability judgment: the quantum probability model (Busemeyer et al., 2011) and
the probability theory plus noise model (Costello & Watts, 2014). Both models
assume that people estimate probability using formal processes that follow or
subsume standard probability theory. The quantum probability model predicts
people's estimates should agree with one set of probability theory identities,
while the probability theory plus noise model predicts a specific pattern of
violation of those identities. Experimental results show just the form of
violation predicted by the probability theory plus noise model. These results
suggest that people's probability judgments do not follow quantum probability:
instead, they follow the rules of standard probability theory, with the
systematic biases seen in those judgments due to the effects of random noise.

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