What if the brain can perceive more signals but that the most common signals are those that are "known" to be captured by the average of the population?

To put it another way, there could also be cases where what is deemed an hallucination isn't, but it might lead to psychosis if the subject doesn't know how to interpret the new signal.

To reason by analogy, that would be akin to everyone being blind and a couple people developping sight.

Whole point is that unless we can understand what the brain is doing, we simply observe a phenomenon but we don't know what the phenomenon actually is.

(not talking about drug induced hallucinations, just to be clear)