Then why would you look when someone says 'look, here's a circle square"?
I am humble enough to recognise that I may be wrong. I am told it happens to everyone.
At least photon interaction doesn't appear to involve perceptions of noumena.
I am not following you here.
And many people state -- or certainly believe -- they have "sensed" the noumena, undefinable or not. Of course a behavorist who has not had that experience must assume they are all 'defective' in some way.
Why do you say that? It could just as easily be that the definition of noumena is defective. Verbal behavior is determined by a whole slew of things, including the prescientific vocabulary of the language community. Examination of a claim does not typically involve taking verbal behavior at face value, but rather, employing a functional analysis of the behavior (verbal, in this case) involved. "Defective" is not a terribly useful label, as it allows one to ignore outliers which might be important. A behaviorist is more likely to follow the dictum "the rat is always right", and attempt to determine what conditions are leading to this particular verbal behavior.
If and when he experiences the noumena, will he also declare himself defective?
This behaviorist...is he made of straw?
Only for materialists or admitted dualists. Or for materialists who believe QM nuttiness -- locality fails, many worlds, delayed choice quantum eraser, etcetc -- has no implications for we what deem 'this physical object, here, now'.
How is a noumenal/phenomenal split any less dualistic from a ~materialist's point of view than from a materialist's? The phrasing of the problem is, itself, dualistic by definition. If you deny that, you are addressing a completely different problem.
I not sure what your getting at with that comment?
Descartes was forced to find some way for the mind to influence the body, even though they were fundamentally different "stuff". He chose the pineal gland as the place where a mechanical body was controlled by an immaterial soul. Of course, your 99.999999...% comment still applies; if the soul is immaterial, and a material body exhibits inertia, the soul can't influence even the pineal gland. Either the two realms are different, or they are not. If a soul can influence a body, either it is of the same stuff as the body, or it violates the laws of physics as we understand them. Thus, as you have said often here, dualism is incoherent. "Experiencing a noumenon" is incoherent, when noumena and phenomena are of different realms, and phenomena are defined as what we experience. "Experiencing a noumenon" is an attempt to connect the two, like Descartes' pineal gland. It doesn't work. It is incoherent.