Matthew Hutson in Scientific American:
People mislead themselves all day long. We tell ourselves we’re smarter and better looking than our friends, that our political party can do no wrong, that we’re too busy to help a colleague. In 1976, in the foreword to Richard Dawkins’s The Selfish Gene, the biologist Robert Trivers floated a novel explanation for such self-serving biases: We dupe ourselves in order to deceive others, creating social advantage. Now after four decades Trivers and his colleagues have published the first research supporting his idea. Psychologists have identified several ways of fooling ourselves: biased information-gathering, biased reasoning and biased recollections. The new work, forthcoming in the Journal of Economic Psychology, focuses on the first—the way we seek information that supports what we want to believe and avoid that which does not.
In one experiment Trivers and his team asked 306 online participants to write a persuasive speech about a fictional man named Mark. They were told they would receive a bonus depending on how effective it was. Some were told to present Mark as likable, others were instructed to depict him as unlikable, the remaining subjects were directed to convey whatever impression they formed. To gather information about Mark, the participants watched a series of short videos, which they could stop observing at any intermission. For some viewers, most of the early videos presented Mark in a good light (recycling, returning a wallet), and they grew gradually darker (catcalling, punching a friend). For others, the videos went from dark to light. When incentivized to present Mark as likable, people who watched the likable videos first stopped watching sooner than those who saw unlikable videos first. The former did not wait for a complete picture as long as they got the information they needed to convince themselves, and others, of Mark’s goodness. In turn, their own opinions about Mark were more positive, which led their essays about his good nature to be more convincing, as rated by other participants.