The perception process in the brain has long been thought to be the source
of why sighted testing produces strong statements of preference and
reports of audible differences which disappear when blind testing is used.
Here is another confirmation of this conclusion based on doing brain scans
with regard to such decisions for beverage products. It shows how
preprograming leads to perception differences occuring in the brain, the
parallel of which is the preprograming of marketing/publishing/peer
pressure in the audio context.

http://www.eurekalert.org/pub_releas...-cvp101204.php