Footnote to the preceding

"Mind reading" has always been regarded, for the most part, as a parlor trick. But the line between amusing trickery and intrusive technology has just gotten a little blurrier.

Supporters of a controversial technique called "brain fingerprinting" claim it can be used to reveal your deepest secrets, even against your will. I'm engaging in a certain level of hyperbole there, of course, but in a broad sense it can indeed read your mind.

We organize the world around us through pattern recognition. Something we're experienced before thus presents a pattern we've experienced before - with the result that our brains deal with it differently than with something we've not experienced before. If it's something we have experienced, a characteristic brain wave (called a p300 wave) indicates recognition. Brain fingerprinting works by detecting that wave, the involuntary and instant response to a known pattern.

In short, it's supposed to tell if you already knew something - unreleased details of a crime scene, for example - or not. By the same token, it could also be used to reveal political associations and other areas not directly related to criminal activity.

The FBI has already tested it and its developer, one Dr. Larry Farwell, calls it "highly scientific" and says it has proved 100% accurate in certain tests.

It does have limitations, which will perhaps limit its potential for abuse - or may instead produce it. A big one is that the test supposedly reveals the previous presence of certain information in the subject's mind, information such as, again, the layout of a crime scene. But studies of memory, particularly the problem of "false memories" and the surprising find of how easily they can be created, have revealed that memory and imagination are closely linked: Test subjects who imagined a certain kind of experience showed the same areas of their brains being active as those who recalled an actual one.

What that means is that an innocent suspect who has thought about the crime and who imagined it with some degree of accuracy could react to a picture of the crime scene with recognition and be labeled guilty. The technique thus should only be used to exonerate (since lack of prior knowledge should be an indication of innocence), not to accuse. But that, of course, doesn't mean it will be.

That's especially true in political cases, including "terrorism" investigations, where people have sometimes been connected to terrorist acts simply (and solely) on the basis that they were familiar with the perpetrators of them.

The day of literal "thought crimes" creeps closer.