While most scientists believe schizophrenia hampers patients' intellectual ability, one intriguing study in England suggests that people with the disease might actually be more logical than the rest of us.
Gareth Owen, a research psychiatrist at King's College London, tested people with schizophrenia and a matched group of people without the disease on how well they did at detecting flaws in syllogisms.
He presented the groups with two types of syllogisms.
In one case, he gave them syllogisms that were nonsensical. "All buildings speak loudly; a hospital does not speak loudly; therefore, a hospital is not a building."
In the other, he gave them syllogisms that fit more with common sense experiences: "If the sun rises, then the sun is in the east; the sun is in the east; therefore, the sun rises."
In the first example, most people know that buildings don't talk, so they can evaluate the syllogism based on its abstract logic, and in this case, the syllogism is valid -- if a hospital doesn't speak loudly, it cannot be a building.
In the second example, most people know the sun does rise in the east, he said, so it is harder for them to see that the syllogism is invalid. The flaw in this case is that, as the syllogism is written, the sun could be in the east and not be rising.
People with schizophrenia did better than the control group overall on figuring out which syllogisms were valid, but performed especially better on the common-sense syllogisms that were wrong, Dr. Owen said.
"I think for many people in psychology and psychiatry, the results are rather surprising," he said, "because they have gotten used to thinking of delusions as an impairment of logical thought. This study runs against that trend."
The real challenge for people with schizophrenia may not be their logic, but their lack of "common sense" in the broadest meaning of that term, Dr. Owen said.
"I think you could say that the dumb constraints of common sense that guide people in their everyday thinking are possibly less strong in people with schizophrenia," which may explain why they could detect invalid syllogisms on topics that involved common-sense experiences.
This difference in thinking may also explain why people with the disease adamantly believe in things the rest of us would reject, he said. A schizophrenic patient may believe that people at a restaurant are all talking about him, for instance, when most of us would assume they were not that interested in us.
"It seems to me what is often happening is that people who are very psychotic will see meaning everywhere. The sense we would have is that all those sensations would be checked against ordinary common sense conclusions," but people with schizophrenia don't have that shared context.
One lesson of his study, Dr. Owen said, is that people with schizophrenia can "advance our understanding of human nature, and I would say we owe it to people with schizophrenia to recognize their position in this respect. I think too often they're characterized as people who have nothing to offer, and I think that is a false characterization."
Mark Roth: email@example.com or 412-263-1130.