# Definitely maybe and possibly even probably: efficient communication of higher-order uncertainty

- Michele Herbstritt,
*Universitaet Tuebingen, Tuebingen, Baden-Wuerttemberg, Germany*
- Michael Franke,
*Universitaet Tuebingen, Tuebingen, Baden-Wuerttemberg, Germany*

## Abstract

Possibility and probability expressions, like possibly or
probably,
are frequently assumed to communicate that the probability
of a proposition is above a certain threshold. Most previous
empirical research on these expressions has focused on
cases of known objective chance: if the true objective probability
is given, would a speaker use possibly, probably or one
of their kin? Here, we investigate the use of probability expressions
when speakers have subjective uncertainty about objective
chance, i.e., higher-order uncertainty. Experimental data
suggest that speakers’ choices of a probability expression is a
complex function of their state of higher-order uncertainty. We
formulate a computational probabilistic model of pragmatic
speaker behavior that explains the experimental data.

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