Illustration: Paula Scher/Pentagram START
Previous: A State-By-State Look at Where Cell Phones and Driving Don’t Mix Trolling down the street in Manhattan, I suddenly hear a woman's voice.
"Who's there? Who's there?" she whispers. I look around but can't figure out where it's coming from. It seems to emanate from inside my skull.
Was I going nuts? Nope. I had simply encountered a new advertising medium: hypersonic sound. It broadcasts audio in a focused beam, so that only a person standing directly in its path hears the message. In this case, the cable channel A&E was using the technology to promote a show about, naturally, the paranormal.
I'm a geek, so my first reaction was, "Cool!" But it also felt creepy.
We think of our brains as the ultimate private sanctuary, a zone where other people can't intrude without our knowledge or permission. But its boundaries are gradually eroding. Hypersonic sound is just a portent of what's coming, one of a host of emerging technologies aimed at tapping into our heads. These tools raise a fascinating, and queasy, new ethical question: Do we have a right to "mental privacy"?
"We're going to be facing this question more and more, and nobody is really ready for it," says Paul Root Wolpe, a bioethicist and board member of the nonprofit Center for Cognitive Liberty and Ethics. "If the skull is not an absolute domain of privacy, there are no privacy domains left." He argues that the big personal liberty issues of the 21st century will all be in our heads — the "civil rights of the mind," he calls it.
It's true that most of this technology is still gestational. But the early experiments are compelling: Some researchers say that fMRI brain scans can detect surprisingly specific mental acts — like whether you're entertaining racist thoughts, doing arithmetic, reading, or recognizing something. Entrepreneurs...