before it's in the papers"
August 03, 2010
TO THE WORLD SCIENCE HOME PAGE
Logic found lurking in madness
and World Science staff
Many thinkers have suspected there is a fine line between logic and madness. The Spanish artist Salvador Dali saw that line as virtually nonexistent: to him, the two were sides of the same coin, to be fused into a glorious unity in each artwork.
Now, scientists say they have found that the link between insanity and rationality may be more than a fanciful notion.
In some situations—limited ones—they have found that schizophrenics have a leg up over the rest of us in reasoning. This advantage, the researchers add, stems from the patients’ very lack of what we typically call common sense.
Schizophrenia, a long-term mental disorder involving delusions and a derailed sense of reality, disrupts people’s ability to see the “context” of events, a key part of common sense, said Emmanuel Mellet, one of the researchers.
Sometimes that inability may become an advantage, because context can lead a thinker astray. “This advantage is patent only in very specific situations where context acts as a trap,” explained Mellet in an email.
Mellet, of the Universities of Caen and Paris-Descartes in Paris, and a group of colleagues presented a set of logic problems to 26 schizophrenics and an equal number of healthy patients. One type of problem in particular was designed to turn context into a trap; 90 percent of healthy people typically fail it, the researchers said.
This type of problem presents the test-taker with 12 different, colored shapes: circles, squares, triangles and diamonds. Also, a “rule” is described to the test-taker, which, if followed, would govern how to put the shapes next to each other in pairs.
But the rule isn’t meant to be followed. The instructions are to break the rule.
The problem is convoluted, and easily leads a problem-solver astray. The rule to be broken is, for example, the following: “if there is not a red square on the left, then there is a yellow circle on the right.”
There are many more right than wrong solutions possible for such a problem. For the above, an answer would be correct as long as the test-taker put anything except a red square on the left, and anything except a yellow circle on the left.
Yet “sane” people usually give wrong answers. For the above problem, they would often put a red square on the left and a yellow circle on the right, quite compatible with the dictum they’re supposed to break.
The trouble is that participants typically make a misplaced use of common sense, Mellet and colleagues said.
Common sense dictates that “using an item or performing an action preceded by ‘not’ is generally a good way to break the rule,” they explained in a paper in the April 21 issue of the journal Schizophrenia Research. But that doesn’t work here.
Although there are several interpretations of what goes wrong when people do this problem, they wrote, one is that the context is “a trap: the presence of the word ‘not’ together with the visual presentation of the figures quoted in the rule” triggers the misleading logic.
Fifty-eight percent of healthy participants failed such problems on all eight tries that they were given, the researchers said. Only 19 percent of schizophrenics suffered this failure rate.
“We suggest that, thanks to their difficulty in processing contextual information, the schizophrenic patients ignored the elements that misled healthy participants,” the researchers wrote. Other interpretations of the findings are also possible, they added, and there might also be more than one correct interpretation.
Mellet and colleagues noted that similar findings came earlier this year from researchers at King’s College London.
The King’s College researchers, who presented their results at the Biennial Winter Workshop on Schizophrenia Research in Davos, Switzerland in February, found that schizophrenics solved a logic problem correctly more often than healthy people did.
This findings supported the idea that “decision-making in people with schizophrenia is less influenced by common sense and more influenced by theoretical reason” than in normal people, the researchers wrote in a summary of their findings.
Mellet’s group wrote their their finding “prompts us to not characterise schizophrenia as a collection of cognitive deficits, but rather as a particular cognitive profile that, in some circumstances, can be more suitable than the cognitive profiles found in normal subjects.”
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