Choice blindness

New Scientist has a fascinating article on some ‘I wish I’d thought of that’ research that looks at how we justify our choices, even when the thing we’ve chosen has been unknowingly swapped. It turns out, most of the time we don’t notice the change and precede to give reasons for why the thing we didn’t choose was the best choice.

It’s a fantastic use of stage magician’s sleight of hand to make a change outside conscious awareness.

We have been trying to answer this question using techniques from magic performances. Rather than playing tricks with alternatives presented to participants, we surreptitiously altered the outcomes of their choices, and recorded how they react. 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”.

The idea riffs on the well-known psychological phenomenon of change blindness but this is also a lovely example of what Daniel Dennett called “narratization”, the ability of the mind to make a coherent story out what’s happening, with you as the main character, even when it’s clear that the outcome was determined externally. In a well-known article, Dennett cites this process as the key to our understanding of the ‘self’.

This was vividly demonstrated in split-brain patients who can be shown images to each independent hemisphere.

Each hand picks out a different picture, because the information is only accessible to the side that controls action for one side of the body, but when asked why they chose the two, they give a story of why the two pictures are related, even though they’re not conscious of initially seeing both pictures.

There’s a great summary in this New York Times piece from 2005, that comes highly recommended.

The New Scientist article covers this new technique for investigating this process with a nifty video of the slight-of-hand in action.

Link to NewSci on ‘Choice blindness: You don’t know what you want’.