Yup
One time a fellow and I were comparing two different machines, in a worked out urban turf zone in a park. Our purpose was to see how they stack up against each other for deep coins, TID ability, etc... The other fellow as a dealer, who was (of course) already quite biased for the machine he'd brought out to compare. I mean, go figure, he's a dealer afterall, and he probably wanted/hoped his machine would do well in this test (because we both knew we were going to post the results to our friends on a local forum).
During the test, I looked long and hard for signals which I could guess were going to be deep high conductors. Ie: wheaties, silver, or whatever, and would then call him over to see what he thought about the signal, from his machine's perspective. I noticed that the fellow would invariably agree "yup, it sounds good. I'd dig it. Could be a deep coin", etc... I began to wonder if he was just subconsciously saying this, looking for reasons in his mind to call the signal good, since .........afterall, I was only calling him over to show him "good" signals, afterall.
So I did a little secret test: I purposefully chose a signal which was one that was probably going to be a beaver tail or foil wad, or nail false, or some other such signal. And SURE ENOUGH, he comes over, and starts detailing the sound signature, tail, TID on his screen, etc... blah blah blah. And sure enough, when we dug it, it was trash
But what happened next, was an interesting lesson in the psychological factor: He started saying how ....... in retrospect, the signal had some bad elements of not sounding so good, and sort of brought to the forefront any indication of de-merits he had previously mentioned, as if to say "yeah, I actually really sort of knew it".
Had it gone the other way, and the signal was a deep silver, he'd have reminded the both of us of the positive attributes he had previously cited, as to how the signal may be a good one.
Thus the psychology of why we *think* we heard something different in gold ring signals. It's all selective memory, that we are all subject to, and just don't realize.