Mailbag: Thrifty brains

Re: The thrifty brainotype.

I have a question about your article "The thrifty brainotype" found at: http://johnhawks.net/weblog/topics/minds/philosophy/clark-2011-thrifty-brains-nytimes.html

Instead of having the whole brain evolve as a single type (information processing efficiency vs energy efficiency) why have only parts of the brain be one way or the other? Given our brain has evolved from much earlier brains, why couldn't a distant ancestor evolve a very energy efficient brain, a later ancestor evolve a visual processing portion that's extremely information processing efficient and then as we come into being take these pieces and keep some pieces and discard others?

Is there any reason why the issue is being discussed as a single whole brain archetype, and not as a piecemeal "some of this and some of that" type?

Thanks so much for this question. I agree entirely, on a functional and evolutionary level of analysis, there is no reason why different cognitive systems should be constrained in the same way. I take Clark's model as a heuristic of how "brain" might be organized along information processing lines, but I think the heuristic fails at the level of a whole organism.

In contrast, the "expensive brain" heuristic really does apply at the organismal level because brain tissue uses energy, and the brain mass is a useful (if imprecise) way of considering energy consumption.

I don't think we can break up the brain into functional modules uncritically, but there are only certain ways in which it is useful to consider it as a whole.