Was He Fat? I Didn’t Even Notice

August 24, 2009
Posted by Jay Livingston

At least two or three times a semester, I’ll tell my class that people don’t really know why they do what they do. Nobody believes me, so I rephrase the idea: We are often unaware of many things that affect our behavior.

Sometimes, we pay a price for that ignorance.

In an experiment reported this year, Eugene Caruso and colleagues told volunteers that they would be competing in a sort of trivia contest, and they could choose their teammates. They were shown pictures of the potential teammates and given information on three variables, each with three categories)

• Education (High School, B.A., M.A.)
• IQ (23, 93, 104)
• Experience (never played the game before, played 3 times, plays every week)

Oh, and one more thing. The person in the picture could be either thin or fat.

Researchers asked the subjects, 101 college students,* why they made the choices they did – that is, which criteria were most important in their decisions. Weight, which has nothing to do with winning trivia contests, was the big loser. On a 9-point scale, the students rated it 2.5 in importance; the other factors were rated 4.9, 6.4, and 5.2, respectively.

But the data on actual choices told a different story. Weight accounted for more of the variance than did any other variable, about 25%. “Participants gave up about 11 IQ points to have a thin rather than overweight teammate.”

Three points here.

• First, the students discriminated against fat people.
• Second, they were unaware of how their own prejudices involved.
• And third, when you ask people why they did something, what you get is not an accurate assessment of factors that actually affected their behavior. Instead, people mention those factors that should rationally be at work.**

*For reasons not explained in the paper, these were Bulgarian students. The title of the paper is, “101 Bulgarians – Using Conjoint Analysis to Detect Discrimination Revealing Covert Preferences from Overt Choices.” Just kidding about the part before the dash. Bulgaria is not all that far from Dalmatia, but Cruella DeVil is not even in the footnotes.

** The classic statement of this idea is Nisbett and Wilson’s “Telling More Than We Can Know: Verbal Reports on Mental Processes,” Psychological Review 84 (May 1977), pp. 231-259.