"choice blindness" and post-hoc rationalization

NewScientist has a recent article about a phenomenon related to the halo effect called "choice blindness."

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"....

Importantly, the effects of choice blindness go beyond snap judgements. Depending on what our volunteers say in response to the mismatched outcomes of choices (whether they give short or long explanations, give numerical rating or labelling, and so on) we found this interaction could change their future preferences to the extent that they come to prefer the previously rejected alternative. This gives us a rare glimpse into the complicated dynamics of self-feedback ("I chose this, I publicly said so, therefore I must like it"), which we suspect lies behind the formation of many everyday preferences.

Read the whole thing to learn the scope of "choice blindness," and how it points to an everyday sort of epiphenomenalism.