On the Media from NPR recently ran a piece called "Your Brain on Commercials." (This sounds like a reference to the famous anti-drug commercials with the tag line: 'This is your brain on drugs.')

A company called EmSense hooks people up to a machine and then records how their brain responds while they watch an ad. The goal is to work out how people are really responding, not how they say they are responding. In the example NPR uses, EmSense could determine what portions of the ad produced a negative reaction in the test subject (in this case, the reporter).

Sounds good, doesn't it? Just hook someone up and you'll know exactly what they're thinking. But these are not mind-reading machines; all they're tracking are bodily reactions. The "whys" of the reaction are unknown (and so far unknowable) relying just on a machine.

There's a societal tendency to look at high tech equipment and the trappings of science and feel that this combination will deliver a truth that is otherwise unknowable. What it actually delivers is a lot of data that is subject to interpretation.

So this approach has some obvious limitations as to the depth of information it provides and the guidance it can give. I'm not saying it's useless — far from it — but it should be used with other more traditional techniques.

There is also a moral question about studying people's brains in action in terms of its invasiveness and how subject it is to abuse. This is a concern, though I doubt the current technology is informative enough for it to be a big problem.