What we expect is what we get

I just read an article in "Psychologies" (Sept 2006) about how some people hoaxed their way into mental institutions in 1972 by faking symptoms of schizophrenia. The article's author, Claudia Hammond, makes this observation:

"What fascinates me... is that once a patient was diagnosed with schizophrenia, anything they did was taken as confirmation that this was true...once we have a view of what somenoe's like, we look for anything that backs our ideas and explain away any evidence to the contrary."

I think that's quite an astute observation.