Saturday science subject: Choice blindness

— 3:26 PM on April 18, 2009

Some folks pride themselves on being able to make snap judgments quickly. But according Lars Hall and Petter Johansson of Lund University in Sweden, people can be surprisingly unobservant when an item they choose is swapped out for something else. As Hall and Johansson explain in their New Scientist article, that "choice blindness" applies even with apparently clear, binary choices:

For example, in an early study we showed our volunteers pairs of pictures of faces and asked them to choose the most attractive. In some trials, immediately after they made their choice, we asked people to explain the reasons behind their choices.

Unknown to them, we sometimes used a double-card magic trick to covertly exchange one face for the other so they ended up with the face they did not choose. Common sense dictates that all of us would notice such a big change in the outcome of a choice. But the result showed that in 75 per cent of the trials our participants were blind to the mismatch, even offering "reasons" for their "choice".

Hall and Johansson say they've documented the same behavior with subjects shopping in a supermarket, shopping online for laptops or cell phones, and even looking for apartments. The researchers say they're currently investigating "moral and political decisions, a domain where reflection and deliberation are supposed to play a central role, but which [they] believe is perfectly suited to investigating using choice blindness."

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