Suppose you need to see a dermatologist. Your friend recommends a doctor, explaining that “she trained at the best hospital in the country and is regarded as one of the top dermatologists in town.” You respond: “How wonderful. How do you know her?”
Your friend’s answer: “We met at the Republican convention.”
Knowing a person’s political leanings should not affect your assessment of how good a doctor she is — or whether she is likely to be a good accountant or a talented architect. But in practice, does it?
Recently we conducted an experiment to answer that question. Our study, done with the researchers Joseph Marks, Eloise Copland and Eleanor Loh for the journal Cognition, found that knowing about people’s political beliefs did interfere with the ability to assess those people’s expertise in other, unrelated domains.
In our experiment, we assigned people the most boring imaginable task: to sort 204 colored geometric shapes into one of two categories, “blaps” and “not blaps,” based on the shape’s features. We invented the term “blap,” and the participants had to try to figure out by trial and error what made a shape a blap. Unbeknown to the participants, whether a shape was deemed a blap was in fact random.
First, the participants received feedback about whether their answers were right. (Because answers were deemed to be correct at random, their success rate was around 50 percent.) They also observed the answers of four other “co-players” who were completing the same task. The co-players were actually computer algorithms designed to appear to perform the task with various levels of proficiency.
At the same time the participants were also asked whether they agreed or disagreed with a large number of statements about politics — for example, “Building a wall along the southern border would reduce illegal immigration.” They also observed the responses of…