The New Scientist recently reported an experiment that somewhat deflates the nonsense that has become the popular interpretation of Benjamin Libet's 1983 experiment relating to measuring the brain activity involved in moving a finger. The popular interpretation is that the signal to move the finger precedes the decision, implying that there is no such thing as free will.
Despite not being in the least bit qualified in this area, I have always felt that Libet's results did not show an absence of free will, simply that we did not understand the process as well as we thought we did, and that the interaction between the conscious and unconscious parts of the brain were closely linked, even in a task that we might have previously thought was entirely in the conscious domain.
The experiments by Jeff Miller and Judy Trevena added an auditory cue to the process, and explored the difference between the left and right sides of the brain (by making the respondent choose whether to move a finger on their left of right hand).
The implications for market research (other than the big philosophical issue about free will) is that we still need to understand that most (possibly all) decisions involve much more than the rational, conscious part of the brain, which is why things like rating scales and intention to buy scales are such poor tools for predicting individual behaviour.