Skip to main content

Schizophrenia and Logic

Mental Health Awareness Weeks logo
Today, 10th October 2014, is World Mental Health Day. This year it is dedicated to living with schizophrenia. On this important occasion, Gareth Owen kindly agreed to discuss his fascinating work on schizophrenia and logic. Gareth is Clinical Senior Lecturer at the Institute of Psychiatry, Psychology and Neuroscience, King's College London.


People with schizophrenia do worse than others on many tasks. Indeed a global conclusion in the psychology of schizophrenia is that people with this disorder have somewhat lower IQ than those without – a conclusion that makes schizophrenia seem a disorder of cognition like dementia or learning disability. But this is an incomplete perspective. The phenomenology of schizophrenia also points in the direction of representational overactivity (1). Additionally, delusions, which people with schizophrenia often exhibit, are not explained by failures of formal inference such as inability to reason with modus ponens or modus tollens or inability to adhere to Bayesian updating norms. That is striking when one considers that delusion and illogically are often assumed to be the same.

Gareth Owen
As a psychiatrist in training at the Maudsley Hospital in London I devised some syllogisms that pitted formal logic against common sense such that, in each syllogism, “truth” was conflicted. I conjectured that people with schizophrenia, in comparison with healthy volunteers, would tend toward logic and away from common sense. Results confirmed this (2).

To give a feel for the data, here are some contrasting responses to one of the syllogisms: If the sun rises then the sun is in the East, The sun is in the East, Therefore, the sun rises.

People with schizophrenia:

• “False. One can never predict out of habit what is the ultimate routine”
• “False. It doesn’t mean the sun rises in the east. It could be in the east and setting. It’s possible”.

Healthy controls:

• “True. Because the sun does rise in the east”
• “True. The sun does rise in the east. I’ve seen it”

 In a recent study in a Danish sample (3), the superior logical performance I found was not replicated – implying the syllogisms are a somewhat unreliable way of exploring rationality in schizophrenia. But the methodological differences between the studies raise some interesting questions about how logic experiments should be conducted to capture phenomena of interest.

Another development is in schizophrenia and symbolic logic. Are people with schizophrenia operating with a different logic? Selesnick (4) has done some lovely work showing how a logic underpinning the mathematics of quantum mechanics can be used to derive observed thinking anomalies in people with schizophrenia including the classic case of a patient who abhorred war and took himself to be Switzerland. A logical judgment if shared attribute implies identity.

Schizophrenia and logic have an affinity and logicians have contributions to make in unraveling this most mysterious of disorders.


References

1) The Maudsley Reader in Phenomenological Psychiatry (2013) Eds. Broome, M., Harland, R., Owen, G., Stringaris, A. Cambridge University Press.

2) Owen, G., Cutting, J. & David, A. S. 2007. Are people with schizophrenia more logical than healthy volunteers? British Journal of Psychiatry 191; 453-454.

3) Revsbech, R. et al. Exploring Rationality in Schizophrenia. (in preparation)

4) Selesnick, S. A. & Owen, G. S. 2012. Quantum-like logics and schizophrenia. Journal of Applied Logic 10; 115-126.
Labels:

Popular posts from this blog

Delusions in the DSM 5

This post is by Lisa Bortolotti. How has the definition of delusions changed in the DSM 5? Here are some first impressions. In the DSM-IV (Glossary) delusions were defined as follows: Delusion. A false belief based on incorrect inference about external reality that is firmly sustained despite what almost everyone else believes and despite what constitutes incontrovertible and obvious proof or evidence to the contrary. The belief is not one ordinarily accepted by other members of the person's culture or subculture (e.g., it is not an article of religious faith). When a false belief involves a value judgment, it is regarded as a delusion only when the judgment is so extreme as to defy credibility.
Read more

Rationalization: Why your intelligence, vigilance and expertise probably don't protect you

Today's post is by Jonathan Ellis , Associate Professor of Philosophy and Director of the Center for Public Philosophy at the University of California, Santa Cruz, and Eric Schwitzgebel , Professor of Philosophy at the University of California, Riverside. This is the first in a two-part contribution on their paper "Rationalization in Moral and Philosophical thought" in Moral Inferences , eds. J. F. Bonnefon and B. Trémolière (Psychology Press, 2017). We’ve all been there. You’re arguing with someone – about politics, or a policy at work, or about whose turn it is to do the dishes – and they keep finding all kinds of self-serving justifications for their view. When one of their arguments is defeated, rather than rethinking their position they just leap to another argument, then maybe another. They’re rationalizing –coming up with convenient defenses for what they want to believe, rather than responding even-handedly to the points you're making. Yo...
Read more

Models of Madness

In today's post John Read  (in the picture above) presents the recent book he co-authored with Jacqui Dillon , titled Models of Madness: Psychological, Social and Biological Approaches to Psychosis. My name is John Read. After 20 years working as a Clinical Psychologist and manager of mental health services in the UK and the USA, mostly with people experiencing psychosis, I joined the University of Auckland, New Zealand, in 1994. There I published over 100 papers in research journals, primarily on the relationship between adverse life events (e.g., child abuse/neglect, poverty etc.) and psychosis. I also research the negative effects of bio-genetic causal explanations on prejudice, and the role of the pharmaceutical industry in mental health. In February I moved to Melbourne and I now work at Swinburne University of Technology.  I am on the on the Executive Committee of the International Society for Psychological and Social Approaches to Psychosis and am the Editor...
Read more