Dr. LANGLEBEN: We take those images and superimpose them on those (points to brain scan) to be able to accurately locate areas of changed activity.

DE SAM LAZARO: Functional MRIs were conducted on 35 subjects in two studies at Langleben's University of Pennsylvania lab.

Dr. LANGLEBEN: I was pleasantly surprised to see that there are parts of the brain that showed increased activity when the person is telling a lie. However, there was no part of the brain that showed increased activity when the person is telling the truth.

DE SAM LAZARO (to Dr. Langleben): So we are naturally inclined to tell the truth?

Dr. LANGLEBEN: Correct. In fact, when you think about it, this is expected because we know the truth and we don't know the lie, so it should require additional effort.

DE SAM LAZARO: Dr. Langleben cautions his work is still in its infancy and may never result in a reliable lie detector test. But ethicist Arthur Caplan says it may not need to be accurate to be used, or perhaps misused.

Dr. CAPLAN: If somebody says, for example, today, "I am not a pedophile," well, then I think you could show them stimuli and try to get measurements of their brain that might give you some information about whether that is true or not. I wouldn't use it to diagnose the condition, but for some purposes right now -- for job employment, or let's say you are trying to screen people for national security reasons or to enter religious orders. Maybe you don't care if it's 100 percent accurate. You are just going to avoid people who might be problematic. That technology exists today.

DE SAM LAZARO: So far, brain imaging technology has taken only baby steps out of the lab and into the outside world.

Adam Koval works for one of the first for-profit neuromarketing companies in the world. It is studying how consumers think and respond to marketing messages. It's information that could never be discerned from the focus groups most marketers use today.

ADAM KOVAL (Bright House Institute for Thought Sciences): There are a lot of inherent biases in focus groups, the need for someone to feel like they are presenting you with information that you want to hear. If you say, "Do you like this product?" They will say "Yes," but they can't articulate it on an analytic scale.

DE SAM LAZARO: Beyond commercial uses of brain imaging, there are also compelling social applications. Just as brain imaging can tailor effective marketing messages, it could also help create better antidrug campaigns, for example. The question Caplan says we'll ask increasingly is, "At what cost to our privacy?"

Dr. CAPLAN: I think our ability to protect our confidentiality and our privacy will be put in peril by this technology. Not because we can't legislate privacy, but those who have the goods will say you have to yield that privacy in order to get them. So you want this job? Yield this privacy.

DE SAM LAZARO: A couple decades from now, Caplan says neuro-imaging could revolutionize our whole concept of self. It could tell us that choices or behaviors we thought were of free will are actually predetermined, the result of our brain's wiring.

Slowly, it seems, the line is blurring where the neurons end and free will begins.

For RELIGION & ETHICS NEWSWEEKLY, this is Fred De Sam Lazaro in Atlanta.