Experiment finds schizophrenics do not take account of visual contexts

• The study, published in the journal Current Biology, used an illusion where an object's contrast appears reduced by its surroundings.
• A medium-contrast patterned disc was shown to volunteers, who had to judge its appearance in the presence of a high-contrast background.
• Of the 15 participants with chronic schizophrenia, 12 were found to make more accurate judgments than the most accurate person in a control group of 33 non-schizophrenic volunteers.
• Dr Steven Dakin, of the UCL Institute of Ophthalmology, says: "We often think of people with schizophrenia as not seeing the world the way it really is -- for example, during hallucinations -- but we have shown that sometimes their vision can be more accurate than non-sufferers.
• "The trick here was to use an illusion where a failure to use context worked to the advantage of people with schizophrenia.
• This was critical because people can perform poorly for lots of reasons, but superior performance tends to be for a specific reason and is more revealing of the underlying cause.
• "Our findings may shed some light on the brain mechanisms involved in schizophrenia.
• Normally, contextual processes in the brain help us to focus on what's relevant and stop our brains being overwhelmed with information.
• This process seems to be less effective in the schizophrenic brain, possibly due to insufficient inhibition -- that is, the process by which cells in the brain switch each other off."