Rejecting Outliers: Surprising Changes Do Not Always Improve Belief Updating

An important human skill is the ability to update one's beliefs when they are no longer supported by the environment. Current models of dynamic decision-making suggest that more unexpected, or "surprising," events lead to quicker belief updating. The current article tests the ubiquity of the notion that surprising environmental changes are always positively related to updating. Using a novel task based on the game Plinko, we tracked participants' beliefs as they learned distributions of ball drops. At an unannounced point during the task, the distribution of ball drops changed and we computed how surprising these changes were relative to participants' beliefs and compared how this surprise factor influenced their ability to update their beliefs to reflect the change. We found that, consistent with current models, there were some situations in which belief updating was positively related to the surprise of a change. However, we also found a situation in which highly surprising changes were negatively related to updating-situations where participants tended to update less with increasingly surprising changes. This negative relationship seems due to participants' treating highly surprising events as "outliers" and choosing not to integrate them in their current beliefs. Our results provide a novel and more nuanced representation of the relationship between surprise and updating that should be considered in models of dynamic decision-making.