The second factor is another brain-related condition. Whether we admit it or not, our minds work inside what is referred to as a "Belief System". It is formed within our subconscious as a sort of "short cut" that reduces the processing needed to carry on day-to-day. As anyone who has struggled to study a difficult subject in school, or to solve a puzzle, or take an exam, thinking is "hard" and takes energy. The brain is always looking for ways to reduce the energy it consumes by difficult thought.
Thus over time we form Belief Systems that control our behaviour day-to-day. The Belief System allows us to make decisions without reverting to difficult, energy consuming thought, by simply applying a sort of rule to the problem, the rule based on previous experience.
Thus if your Belief System is based on experience whereby you have not noticed much (or any) difference in cables, and thus holds that cables "do not matter" then you are unlikely to hear a difference during or after a cable break-in period, regardless of the actual effect.
Similarly, if your Belief System involves an experience in the past whereby you did hear a difference while auditioning a change involving only a cable, you are more likely to accept the idea that cable break-in might affect performance.
Perhaps stick with EE as this "belief system" is complete gibberish. You may be well versed in the EE field and thus throwing in some "self-help" grade references from Oprah Show psychology will only discredit your EE knowledge.
The reason I write this is because I don't think solid arguments need flawed examples or explanations.
What you gently brushed against from afar, to be polite, is the process of forming of the stereotypes. At the same time this has nothing to do with belief and can't be used to further the debate on cable break in. It is even further flawed with your explanations of difficult puzzles and subjects in school.
Noticing that human thought process is very susceptible to forming stereotypes lead scientists (not only psychologists, but many of those who have evolution as middle ground) to assume that this mechanism must have been useful for human species to strive.
The simplest way of explaining is this: instead of trying to discern nuances in a roar of a predator animal in order to identify which one it is, all roars are processed as danger and "flight or fight" is engaged. The time needed to discern whether it is really a threat can be fatal. "Energy consuming" is not the issue here at all, as one might argue that it might even save energy to
not run from a donkey. This mechanism eliminates risk, this is its primary function. One more reason why it is utterly useless in listening among cables comfortably plunged into the armchair with no threat whatsoever.
Also it was never even proposed that the fact that all roars fall into "danger" category in any way imply you hear no difference among them. On the contrary, even when you don't know what it is, you're still able to say what it's not. So, after some time you might even stop running from donkeys and this is desirable in the end.
For this mechanism experience is not needed, this is passed on and can be detected in people who never met with the danger. People run from snakes when they first see them. People who never fell from height are afraid from height...
The entire "psychology" section of your post boils down to something similar to "if you look for it you'll find it", which brings no clarity to the topic as we are back on the beginning asking ourselves who is wrong; people who expect difference and hear it or people who expect no difference and don't hear it, is it those looking for difference or those looking for no difference. Both will not be correct.
For your purpose you might look for an experiment with a match box filled with led. This is where former knowledge forms your action and almost no one ever managed to lift this matchbox in first go, unless he was let in on it. IMPORTANT - they were ALL able to lift it the next time they tried. No idiot ever came forth who tried over and over again while applying the same amount of strength needed to lift the plain matchbox.
