Although the term "IQ" is no longer much in vogue with IQ experts, you still hear it often enough on the street. Ask 20 people what it means, and most of them will likely say "intelligence." Press for a longer definition and you might hear, "It's your intelligence score."

That concept--intelligence score--is one that's worth deconstructing.

What's in a phrase?
In our quest for the meaning of IQ, let's leave aside the multiple-intelligences argument for now. That's the recent theory that says there are eight to ten--and maybe more--types of intelligence. And it makes the term "smart" even more ambiguous.

If the concept of "smart" is hard to nail down, "smarter" at least makes intuitive sense. No matter how you define intelligence, some people surely have more of it than others.

And if  "smarter" makes sense, then it must be possible, at least theoretically, to measure "exactly how much smarter."

But when you start talking about "exactly how much smarter," you rely, I think, on a certain underlying image of intelligence and intelligence testing.

Is the brain like a bottle?
In this image, the brain is a container, and intelligence is a substance in it. An intelligence test, therefore, is like a dipstick. Shove it into the brain, pull it out, and what registers on the measuring stick is the amount of "smarts" in that brain.

But this image isn't accurate, is it? Interesting as poetry, maybe, but not really descriptive of what's happening.

After all, intelligence clearly isn't in the brain, it is the brain. It's less like the oil in the engine and more like the efficiency of the engine as a whole. Every aspect of the engine affects its efficiency, from how finely milled the surfaces are to the grade of oil in the block to the design of the engine.

So how can such a many-sided totality be measured?