November 14, 2005
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.
Posted by bug to Mind and Brain at November 14, 2005 1:38 PM | TrackBackVery interesting study! Some thoughts/observations:
1. Were the participants ever explicitly asked (at the end of the study) if they ever noticed that they had been given the wrong photo? I wonder if some of them noticed the "mistake" but simply chose to say nothing (to avoid confrontation/embarassment). After all, the participant could have had the feeling that this is an "important study" and that the researcher would be very disappointed if a mistake was made, since they would presumably have to start over and/or the trial would be useless. Rather than disappoint them, they might just go along with the "mistake", rather than jeopardize the $20 they were to receive for taking the test.
2. I have to imagine that the photos were pretty close to each other when it comes to overall attractiveness level. If they showed a photo of say, the Wicked Witch of the West vs. Keira Knightly, and then they slid the Wicked Witch photo across the table, I can't imagine that the participant would then wax poetic about her lovely warts and glowing green skin.
3. I would guess that if the participant was asked to justify their decision on *every* choice rather than just a random fraction of them, they would be more likely to catch the researcher giving them the wrong photo. If they knew in advance that they would have to justify every choice, they would be thinking of reasons for their choice before the picture was slid to them. Then, when the photo was slid to them, they might be more likely to realize that their "reasons" they had already been thinking of did not match the photo.
4. Furthermore, since the "justification" task came as a surprise to them, they were probably somewhat taken aback when it was sprung on them. I would guess that the surprise combined with the fact that they been put on the spot and given a new task probably made their brains completely blank on the decision they had just made a second ago. In short, being put on the spot and slightly confused made them more susceptible to the power of suggestion, and more likely to accept what they had been given as "the truth".
So I guess I would say that I see the results of this study as a combination of the above factors (societal pressure not to expose mistakes, choices that were very subjective and faily similar to each other, and being put on the spot to raise the effectiveness of suggestion). If you remove any one of those factors, I'm not sure the study would "work" (but it would be interesting to see if it did).
That being said, I definitely agree that humans can rationalize anything.
-Nat
Posted by: Nat at November 16, 2005 6:49 PM