Having been through a few of these tests (rather than reading someone else's), it IS peer pressure that causes this to happen. The "moderator" pushes people to pick one component over the other all too often.
Well, is this blind or sighted? If sighted, it can be called peer pressure or another term which some call 'priming'. In this case, you've been primed by being provided certain information be it the manufacturer, reviews, appearance, construction, whatever and that lodges itself in your subconcious which then influences your decision. Also, see my recent post in 'Audio Theory' that references a Wall Street Journal (WSJ) article.
When the question is posed as difference or no difference, I have never never seen someone voice that there was a difference when the same component was left in the system.
Craig, if you've got some buddies who are pretty disposed to cable differences, you can try this for yourself. Just fake the switch, but you've got to do a good job at creating the illusion and they mustn't know that you're a sneaky fellow...like me.
When the question is posed along the line of: "Listen for one component to have better bass, and see if you can discern which it is", then the panel is pre-disposed to hear a difference.
Also consider that they may indeed hear better bass because their auditory focus has changed which alters the information that makes its way into the brain.
A suggestion: why not do some of your own tests, rather than relying on posting references to out of print articles ?
Many of the articles cited come from journals and have been replicated by others. Really Craig, for that matter, screw the Pythogorean Theorem, The laws of thermodynamics, and Kirchoff's Laws.