Saturday, May 02, 2009

Book Review: "The Imprinted Brain" - A fascinating genetic theory of mental illness

Book Review: "The Imprinted Brain: How Genes Set the Balance of the Mind between Autism and Psychosis" by Christopher Badcock

Review by Todd I. Stark

A bold new theory of mental illness that could revolutionize our understanding, if it is right.

[See my reviews on Amazon.]

This is a deeply fascinating theory. I gave it lots of stars because of the importance of its ideas, even though it is not a great book in literary or stylistic terms.

The relatively uncommon collaboration of a sociologist (Badcock) and a biologist (Crespi) produced a compellingly simple and symmetric theory of the biology of the human mind which remains remarkably explanatory and coherent around just a few central ideas:

1. The "selfish gene." William Hamilton's insight that genes can sometimes serve their own reproductive ends as much as or more than those of the organism they build.

2. The "imprinted gene." Some genes may be inherited by either parent but only be expressed when inherited from one parent vs. the other.

3. The clinical observation that autism and psychosis are expressed in opposite versions of the same kinds of symptoms.

4. The theory that autistic symptoms represent an extreme of thinking in mechanical terms, and psychosis an extreme of thinking in mentalistic terms, with the two kinds of illness forming a single spectrum of disorders from autistic at one end to schizophrenic at the other.

This is not one of those relatively dull or unlikely theories about how schizophrenics might really be geniuses, or how mental illness might somehow be adaptive. The speculations of the imprinted brain theory go well beyond that sort of thing, making it distinctively broad and potentially testable. Although the book has a few philosophical turns in it, the technical journal articles by Badcock and Crespi make it clear this is a scientific theory that will live or die on empirical data, not primarily a philosophical idea.

The theory itself is half about how paternal imprinted genes serve their own reproductive ends by increasing growth and testosterone and by laterallizing the brain and helping to produce thinking that is optimized for dealing with inanimate things in particular ways. The other half of the theory is about how maternal genes serve their own reproductive ends by cutting back on growth, reducing testosterone, and fostering the development of a kind of thinking optimized for interpreting human intentions.

The theory explains the symptoms of autism as an "extreme male brain" which deals well with things but poorly with people. The symptoms of paranoid schizophrenia are seen as "cancers of the mind" resulting from an "extreme female brain," the extremely fertile creation of human intentions and minds around us from little basis. The idea that the autistic end of the spectrum may be an exaggeration of what we think of as stereotypical male cognitive processes has been suggested by many others since the autism was first identified, but the possibility of the other end of the spectrum being a symmetric case of mentalistic overdrive is a little more original. It also seems to be less well supported by the genetic data so far. But the possibility that a beautifully symmetric theory like this might possibly be validated is the kind of thing theorists get very excited over.

The author put a lot into this relatively small book and made it very readable. The style however is a bit lacking and sometimes can be dull and sometimes abrasive in contrast to the fascination of the content itself. I got the feeling at various points that the author couldn't help throwing in his own editorial comments about pet peeves that might be addressed by aspects of the theory, and I think this sometimes hurt the tone of the book. With such a powerful theory it is very tempting to wield it excessively just to see what it can do.

Overall, though, this book provides a reasonable balance between technical presentation and narrative exposition. It isn't a journal article, although it is based on material that has filled a number of journal articles, and it is not a breezy introduction with award winning science writing. It is a general readership account of a technical theory that has both deep scientific and broader cultural implications ... if it turns out to be right.

The book gives a solid introduction to the patterns of symptoms in various mental illnesses and the historical interpretations that help align each of them with their theory. They introduce just enough genetics so that you can understand why they feel "imprinted genes" help explain the complex idiosyncratic inheritance pattern seen in autism and schizophrenia. They discuss the spectrum of symptoms from several different angles so that you can see just how broadly explanatory this theory could potentially be. The authors briefly discuss some cultural implications of their theory for religion, feminism, science, and so on, a deep area that they only touch on very superficially.

The end of the book raises the interesting possibility that certain exceptional kinds of geniuses may be savants at both ends of the spectrum, extreme male and female brains at the same time, capable of both the overdeveloped mechanical cognition of autistic savants and the overdeveloped intentional sensitivity that the authors hypotheize may represent "psychotic savants."

The book is scattered with supporting quotes from erudite psychotics and high functioning autistics describing in their own words how they think and experience the world.

Reading this book I got a feeling that the theory *could* very well be right and that it seemed to make sense of a lot of otherwise very diverse and sometimes puzzling findings in genetics and psychiatry. I think it's entirely accurate to say that this theory has the potential to revolutionize our understanding of mental illness, especially its genetics, and provide a coherent framework where previously we had only scattered loosely related diagnostic categories and quibbles over them.

If I were to deliberately seek out a fault here, other than the sometimes annoying cultural jabs at religion and feminism, it is that the imprinted brain theory seems to explain too much while taking too much for granted. Explaining all of the dimensions of mental illness through an all-encompassing dimension of cognitive abilities seems to explain too much about thinking and not enough about motivation. Mechanistic thinking is not just thinking about things, it is a fascination, an absorption in things, and likewise for mentalistic thinking about people. The book never really talks about how the different cognitive subsystems relate to the motivation to use them, which seems to be just as important, especially in the case of savants, who provide a significant area of data for the theory. This is a topic that I've seen addressed in Crespi's journal articles, but was not really touched on in the book very much.

As far as validation of the overall theory, I think it will depend a lot on whether both both ends of the spectrum of disorders are found to be the genetic result of a common disease pathway resulting from many different variations of rare alleles or a particular conjunction of common ones. If either end depends on rare alleles, its evolutionary significance is much less likely. The beautiful symmetry of this theory depends very much on both ends of the disorder spectrum having evolutionary significance.

See also Badcock's Edge article:

and the following books on some of the less well known speculative evolutionary genetic ideas underlying this theory:

Genes in Conflict: The Biology of Selfish Genetic Elements

Genomic Imprinting and Kinship (The Rutgers Series in Human Evolution, edited by Robert Trivers, Lee Cronk, Helen Fisher, and Lionel Tiger)

There is some good theoretical backgound to the evolution of reasoning and what we can learn about it from autism in:

Human Reasoning and Cognitive Science (Bradford Books)