Wednesday, August 03, 2011

The Design of the Brain by Evan Lerner



From Print Magazine, this article takes a look at the human brain in terms of design - and the fact that the brain was not designed. Lerner mentions Kluge: The Haphazard Evolution of the Human Mind, by Gary Marcus, a cogent argument that the brain is not designed and is basically a collection of adaptations.

The Design of the Brain

by Evan Lerner

A look at the design of something that wasn’t designed at all.

Since you are reading this sentence, I will make a bold assumption and assert that you have a brain. This is neither sarcasm nor a metaphoric comment on your intellect or taste; this is about the roughly three pounds of squishy tissue between your ears.

Game show fans already have an inkling as to why; IBM finally showed off its natural-language-processing computer Watson on the game show Jeopardy! in February, where it demolished its fleshy opponents. That humanity could only sheepishly grumble about the computer’s buzzer reflexes is a tacit admission that it could basically read and understand the game’s clues as well as any human.

But this is only a bold, and not totally foolish, assumption under certain definitions of the word “read,” since computer programs have been scanning and memorizing this text long before it hit your optic nerves. In fact, everyone involved in the production of this article depends on that ability to effortlessly recall each character and the order it was entered, and to rearrange them into previous patterns at our discretion.

And while they might be able to read, what our computers have no hope at doing—and what Watson is perhaps only scratching the surface of—is coming up with the idea for this article in the first place. So far, the only machine we know capable of that kind of creative behavior is not the product of decades of meticulous engineering, but millennia of haphazard biological evolution. The brain wasn’t designed to think, analyze, or create. It wasn’t designed at all.

But that the brain is the only thing on the planet that can surprise its owner with a novel idea is one of our biggest unanswered scientific questions. What makes us more than meat-machines, programmed to sing, dance, and dream? What makes us human?


The Undesigned

The basic building blocks of the brain are neurons, long, branching cells that communicate with each other via electrochemical signals. The human brain has roughly 100 billion of them, or more than ten times the number of people on the planet. The organism with the simplest nervous system, the nematode, has 302.

To be totally reductionist, everything that happens in the brain can be boiled down to electrical signals in these neurons. The electrical signals cause chemicals known as neurotransmitters to jump the tiny gulf separating a neuron from one neighbor or another, which sets off new electrical signals in the recipient, and so on until you wiggled your left big toe or selected the next word in your sonnet. The difference lies in the pattern of neurons firing and the path through the various parts of the brain that pattern takes.

This process is more or less identical in humans and nematodes, as both species’ neurons are the product of the same slow, incremental changes of evolution. What separates the two species’ nervous systems can be traced back to surviving in the environments of our ancestors and those of a millimeter-long roundworm. Nematodes’ neural development could stop once life’s most basic functions—breathing, eating—were satisfied. The human hindbrain takes care of those, but to get to complex sensory processing, and then to poetry, painting, and neuroscience, the midbrain and forebrain needed to develop on top of it.

But when we concern ourselves with those uniquely human abilities, we’re really talking about the part of the forebrain known as the cerebral cortex and its Frontal, Parietal, Occipital, and Temporal lobes. Broadly speaking, they are respectively the centers of decision-making, spatial perception, vision, and speech. Of course, the actual mechanisms of all of the above involve both higher specialization within each of those lobes and interactions with many other parts of the brain.

The organization, interactions, and specificity of these regions seem so orderly, in fact, that it is tempting to think of them as being designed for their various purposes. But not only did these structures arise from the ground up, through millions of random mutations rather than a concerted effort, they did so in an environment that was largely devoid of the things we think they’re so purpose-built to interact with. To say there’s a part of the brain design for reading ignores the fact that there was nothing to read at the point it tookthe shape it has today.

“I think part of what designers do is try to reverse engineer the human mind to find out what kinds of things will tickle the brain,­­­­­” says Gary Marcus, professor of psychology at New York University, and author of Kluge, an account of the brain’s haphazard evolution. “I don’t think there’s a simple formula for it, because the brain itself is not a particularly simple system.”

In Kluge, Marcus outlines two overlapping thinking systems that evolution bestowed upon the brain: deliberative and reflexive. In the environment these systems evolved, both were useful—you’d need to deliberate with your fellow proto-humans about how to best corner your prey in order to eat, but allow your reactive systems to override your hunting strategy if you suddenly thought youmight be the one on the menu.
There's much more - read the whole article.


No comments: