Hindsight bias — the irrational belief that past outcomes were predictable — is a well-understood psychological phenomenon. Our research suggests that this bias is becoming stronger, thanks largely to an abundance of visual information, including re-creations and simulations. But in measuring it, we’ve also discovered its near opposite, what we call the propensity effect: Visualization may also, in certain circumstances, make people overconfident of impending outcomes.
We presented study participants with traffic situations. Some received a text description with diagrams, and others watched a computer animation. The amounts and types of information varied. Some people examined normal traffic conditions; others saw or read about a driver error but not the resulting accident; still others saw or read about the driver error and the resulting accident.
Hindsight bias more than doubled for the subjects who watched the computer animation. The propensity effect was significantly greater for those who watched the driver error but not the accident: They were more likely to say they could see a serious accident coming than those who actually saw it occur and then were asked if they had seen it coming.
You experience the propensity effect when, say, a baseball that’s hit hard gives you that momentary feeling of “just knowing” it’s going out of the park. People misattribute visual processing of motion to higher-order judgments, such as predicting outcomes. When we gave subjects still photos of the same traffic situations that they could page through at their own pace, the propensity effect wasn’t present.
Computer-animated visualization is appealing because it can help make sense of highly complex information, but it’s also, quite literally, a point of view. The information can be conveyed with certain emphases, shown from certain angles, slowed down or enlarged. (In a sense, all this is true of text as well, but with subtler effects.) By creating a picture of one possibility, they make others seem less likely, even if they’re not.
When an objective reading of evidence is critical, as it is in a courtroom and in many business contexts, both the deepening hindsight bias and the propensity effect can be pernicious.
We don’t suggest doing away with animations. But we need further research to understand the consequences of using them.
(Written by Neal J. Roese who is a professor at Northwestern University and Kathleen D.Vohs is a professor at the University of Minnesota)
