Why such an odd title for a post in a blog about issues relating to autism, neuroscience and mental health issues?  Lately I’ve been thinking about how things are classified. In particular, how the medical establishment classifies mental illnesses, and how diagnoses are meted out.  Many of you chafe at the idea of being defined by a list of behaviors, and rightly so. At what point does a set of behaviors switch from being one’s personality to being an illness? My brother is very low functioning. Does he have autism? Is he retarded? Both? Am I autistic too? High functioning? Do I even have autistic personality traits?

I have much work ahead of me to try understanding the rationale behind the new Diagnostic and Statistical Manual of Mental Disorders (DSM-5). I have no doubt that many smart people worked faithfully on this complicated issue. But before I get into this, I want to review the problems facing classifications of things in general.

Sorting again

I have this problem over and over again: do I sort my books by height, so all the tall books go on the bottom shelf and everything looks nice, or do I sort them by subject, running the risk that the Atlas of the World would be right next to the my teeny set of Pocket Maps of the Appalachian Trail? There are so many subsets of my STUFF, that I am frequently at a loss, with no underlying organizing principle. I don’t think I’m the only one with this problem.

Taxonomy

Taxonomy is the practice and science of classifying things.  Stephen Jay Gould wrote a very interesting essay called Linnaeus’s Luck?[1], in which he discusses the problems faced in classifying plants and animals. Certain scientists looked on this effort as mere ‘stamp collecting’, as if there was a pre-determined slot into which each organism could fit. Louis Agassiz, great scientist of the mid 19th century was of similar mind. Not a believer in evolution, Agassiz thought that each species represented a single expression of God’s will; to know taxonomy was to know God.

Linnaeus

Linnaeus’s Luck, Gould tells us, refers to the fact that Linnaeus’s classification system for modern taxonomy was brought into the world in 1758, when creationist theories were in authority (a full 100 years before Darwin) and survived the transition to the system of branching used by modern evolution theory.

Although the particulars of Linnaeus’s system are not really relevant to this post, it is worth mentioning briefly. Linneaus used two names to describe each species: the generic name (genus) first, followed by the ‘trivial’ name. One can think of his system as a set of nested Russian dolls. Gould gives the example of the domestic dog: If the domestic dog (Canis familiaris) species is in the inner box genus, the next outer box is called the order (Carnivora); the next box surrounding the order box is the class (Mammalia); the next box is the phylum (Chordata); finally the outermost box is the kingdom (Animalia). The organism in the inner-most box has all the traits contained in each surrounding box.

Keep in mind, the problems noted above were in classifying plants and animals: physical entities with physical traits that could be examined by anyone. Behavior on the other hand is not a physical trait and is variable from person to person and not consistently observed. This gives one an idea of the complexity of classifying behaviors.

We need a Linnaeus for taxonomy of behavior. Is that even possible?

Today DSM, tomorrow my room! (maybe vice versa)