11/19/08 - rationalizing choices

In today's excerpt - people's ability to rationalize choices after they are already made:

"Unspoken assumptions and implied information are important to both the perception of a trick and its subsequent reconstruction. Magician James Randi ('the Amazing Randi') notes that spectators are more easily lulled into accepting suggestions and unspoken information than direct assertions. Hence, in the reconstruction, the spectator may remember implied suggestions as if they were direct proof.

"Psychologists Petter Johansson and Lars Hall, both at Lund University in Sweden, and their colleagues have applied this and other magic techniques in developing a completely novel way of addressing neuroscientific questions. They presented picture pairs of female faces to naive experimental subjects and asked the subjects to choose which face in each pair they found more attractive. On some trials the subjects were also asked to describe the reasons for their choice. Unknown to the subjects, the investigators occasionally used a sleight-of-hand technique, learned from a professional magician named Peter Rosengren, to switch one face for the other—after the subjects made their choice.

"Thus, for the pairs that were secretly manipulated, the result of the subject's choice became the opposite of his or her initial intention. Intriguingly, the subjects noticed the switch in only 26 percent of all the manipulated pairs. But even more surprising, when the subjects were asked to state the reasons for their choice in a manipulated trial, they confabulated to justify the outcome—an outcome that was the opposite of their actual choice! Johansson and his colleagues call the phenomenon 'choice blindness.' By tacitly but strongly suggesting the subjects had already made a choice, the investigators were able to study how people justify their choices—even choices they do not actually make."


Susana Martinez-Conde and Stephen L. Macknik


'Magic and the Brain: How Magicians "Trick" the Mind'


Scientific American


December 2008


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