One of the difficulties in behavioral research is precise definition of stimulus-response. The more complex the stimulus, the less precise the definition. In ABX testing, the definition of the cumulative response is trivial: can reliable hear a difference or not. But because the stimulus is likely to be imprecisely defined, absence of reliably making the distinction does not mean there is no difference. For music, Gestalt seems too relevant. That's one of the reasons we know so much about what a rat is likely to do in a maze and so little about what a kid is likely to do in a classroom.
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