As these errors compound, one result is that the mechanisms of perception, undetectable when functioning normally, become more visible--you begin to see how you see, and often one finds that what had been taken for reality during ordinary consciousness was in fact a representation, a drawing one made of reality without realizing it.
But what if they don't have to be errors (not specifically talking about LSD here). What if they can be enhancements. Now, if infrared vision was possible, I guess you could consider the blocking of the visible light response as an error. But a required error. Because the only way a human could see in infrared is if all visible light is filtered. That's the reason you don't see infrared in the dark. It's still there - it's just that our eyes are MUCH MUCH more sensitive to visible light as opposed to IR that even in darkness the IR is overpowered.

But you are completely right about outer/inner perception... altered perception... seems like such a simple yet vague term.