Choice Blindness

One of my favorite psych studies is one where a subject who had had his left and right brain hemispheres severed was asked to point (with either his left or his right hand) to one of four given pictures that matches a test picture. Unbeknownst to the subject, his right eye is shown one test picture (say, of a chicken claw) and their left eye is shown a different one (say, a snow scene). When asked to point with his right hand to the matching picture he picked a chicken, when asked to point with his left he picked the snow shovel. The fascinating part is when the subject was asked to verbally explain why he picked the snow shovel. Language is mostly generated in the left hemisphere (which controls the right hand), the half that didn’t pick the shovel. Rather than look confused, he invariably came up with explanations for why he picked what he did — explanations that the experimenter knew were incorrect like “oh, you need the shovel to clean up the chicken coop.”

Now BPS Research Digest points to a new study where they find the same sort of “choice blindness” in normal subjects:

One hundred and twenty participants were shown 15 pairs of female faces (taken from here). For each pair they had to say which of the two faces they found more attractive, and on a fraction of trials they had to say why they’d made that choice, in which case the photo of the face they’d selected was slid across the table to them so they could look at it while they explained their choice. Crucially, on a minority of these trials, the researchers used sleight of hand to surreptitiously pass the participant the photo of the face they had just rejected, rather than the one they’d chosen.

Bizarrely, only about a quarter of these trick trials were noticed by participants, despite the fact the two faces in a pair often bore little resemblance to one another. Even stranger was the way the participants then went on to justify choosing the face on the card they were holding, even though it was actually the face they’d rejected. It’s not that participants weren’t paying attention to the face they’d been passed – the justifications they gave often related to features specific to this face, not the one they’d actually chosen. Independent raters who compared participants’ verbal explanations for choices they had made (non-trick trials), with their explanations for the choices they hadn’t made (trick trials), found no differences in amount of emotional engagement, degree of detail given, or confidence.

As I’ve said before: Man is not a rational creature. Man is a rationalizing creature.