How do we know there are issues with our senses and that reality exists?

I guess that the other animals do the same...

Pavlovian conditioning–induced hallucinations result from overweighting of perceptual priors. A. R. Powers, C. Mathys, P. R. Corlett. Science  Aug 11 2017, Vol. 357, Issue 6351, pp. 596-600. DOI: 10.1126/science.aan3458

Abstract: Some people hear voices that others do not, but only some of those people seek treatment. Using a Pavlovian learning task, we induced conditioned hallucinations in four groups of people who differed orthogonally in their voice-hearing and treatment-seeking statuses. People who hear voices were significantly more susceptible to the effect. Using functional neuroimaging and computational modeling of perception, we identified processes that differentiated voice-hearers from non–voice-hearers and treatment-seekers from non–treatment-seekers and characterized a brain circuit that mediated the conditioned hallucinations. These data demonstrate the profound and sometimes pathological impact of top-down cognitive processes on perception and may represent an objective means to discern people with a need for treatment from those without.

My comment: We all suffer from hallucinations in our lives... An example is hearing our phone ringing very briefly and very softly when it is not possible that it sounded (no coverage, total isolation, and other phones could not be heard piercing the thick walls). We check and immediately find that no call is pending of being attended to. These researchers found that the cerebellum in some way dispells the hallucination with a constant check of past expectations and beliefs against reality, but some people with schizophrenia hear, with great confidence, sounds or voices ***five times*** more frequently than healthy controls. The more advanced is the illness, the less activity is seen in the cerebellum.