Since
@Hon brought up the idea of terms we shouldn't use, I'd like to suggest that we should be careful of using the term "placebo effect" to explain perceptual biases.
Everyone knows of the placebo effect as it refers to placebos in medical testing. And that's the situation where something that should do nothing has an effect. And granted, it can be seen as a particular type of expectation bias.
And yet, when we're talking about expectation bias and audio equipment, the equipment is always producing sound. So there is some real thing contributing to the overall evaluation of the equipment. There's just some part of it that's wrong. As opposed to placebo effect, where there's nothing real going on.
Consequently, audiophiles get pretty riled up when placebo effect is used because it implies to them that all of what they are sensing is imagination.
Rather, seems better to explain expectation bias as tipping the scales of evaluation.
And while we generally see expectation bias as favoring a piece of equipment, it could also have the opposite effect. For example, if Pyle comes out with a new amp on Amazon that actually measures fairly well, I'm sure I would be biased to think it sounds bad because of the reputation of the brand. lol
Consequently, that's another way the placebo effect doesn't quite fit what we mean by expectation bias in audio.
Thoughts?