…you don’t know the half of it, concludes a new study in the American Political Science Review. Voter biases of various kinds, the study finds, impede their ability to evaluate the performance of politicians dispassionately.

In a series of experiments, researchers from Yale, UC San Diego, and UC Berkeley found that voters “are susceptible to these biases even when given financial incentives to behave otherwise and when the information necessary to avoid these biases was readily available.”

According to the abstract:

In this article, we show that these biases in retrospective evaluations occur even in the simplified setting of experimental games. In three experiments, our participants (1) overweighted recent relative to overall incumbent performance when made aware of an election closer rather than more distant from that event, (2) allowed an unrelated lottery that affected their welfare to influence their choices, and (3) were influenced by rhetoric to give more weight to recent rather than overall incumbent performance. These biases were apparent even though we informed and incentivized respondents to weight all performance equally.

Cambridge University Press, which publishes the American Political Science Review, summarized the study’s findings about voters this way: “They tended to punish or reward the incumbent based on whether or not they had won or lost a lottery, and gave greater weight to earnings closer to the election when they learned about the election closer to it or after certain rhetorical statements. They persisted in this irrational behavior even when it was made clear to them that their fictional incumbent had had nothing to do with the lottery and that events closer to the election were no more informative of the incumbent’s true performance than events further from the election.” (Emphasis added.)

The article itself is, unfortunately, behind a subscription wall.