A pragmatic account of the weak evidence effect
This addresses a challenge in belief updating for cognitive science and decision-making, offering a rational model for social reasoning phenomena.
The paper tackles how listeners account for speakers' persuasive goals when updating beliefs, extending probabilistic models of social reasoning to explain why weak arguments can backfire (the weak evidence effect). It introduces an experimental paradigm (Stick Contest) showing this effect depends on speaker expectations, with their model outperforming alternatives.
Language is not only used to transmit neutral information; we often seek to persuade by arguing in favor of a particular view. Persuasion raises a number of challenges for classical accounts of belief updating, as information cannot be taken at face value. How should listeners account for a speaker's "hidden agenda" when incorporating new information? Here, we extend recent probabilistic models of recursive social reasoning to allow for persuasive goals and show that our model provides a pragmatic account for why weakly favorable arguments may backfire, a phenomenon known as the weak evidence effect. Critically, this model predicts a systematic relationship between belief updates and expectations about the information source: weak evidence should only backfire when speakers are expected to act under persuasive goals and prefer the strongest evidence. We introduce a simple experimental paradigm called the Stick Contest to measure the extent to which the weak evidence effect depends on speaker expectations, and show that a pragmatic listener model accounts for the empirical data better than alternative models. Our findings suggest further avenues for rational models of social reasoning to illuminate classical decision-making phenomena.