  English speakers use probabilistic phrases such as likely to communicate
information about the probability or likelihood of events. Communication is
successful to the extent that the listener grasps what the speaker means to
convey and, if communication is successful, individuals can potentially
coordinate their actions based on shared knowledge about uncertainty. We first
assessed human ability to estimate the probability and the ambiguity
(imprecision) of twenty-three probabilistic phrases in a coordination game in
two different contexts, investment advice and medical advice. We then had GPT4
(OpenAI), a Large Language Model, complete the same tasks as the human
participants. We found that the median human participant and GPT4 assigned
probability estimates that were in good agreement (proportions of variance
accounted for close to .90). GPT4's estimates of probability both in the
investment and Medical contexts were as close or closer to that of the human
participants as the human participants' estimates were to one another.
Estimates of probability for both the human participants and GPT4 were little
affected by context. In contrast, human and GPT4 estimates of ambiguity were
not in such good agreement.
