Vilayanur S. Ramachandran, MD, PhD, is eclectic in his scientific pursuits. The University of California, San Diego, psychology and neuroscience professor has written more than 120 papers on topics including phantom limbs, synesthesia, mirror neurons and autism. He's renowned for using unusual behavioral phenomena as a window into some of humanity's knottiest questions about the nature of consciousness and the self--an approach he takes in his new book, "The Man with the Phantom Twin: Adventures in the Neuroscience of the Human Brain" (Dutton Adult, 2008).

However, Ramachandran is perhaps most famous for discovering the mirror-box technique for stroke rehabilitation. With this procedure, patients watch a reflection of their hand moving in a mirror, which gives the illusion that a person's paralyzed hand is moving in response to the brain's commands. Among amputees, the procedure alleviates phantom pains. Among stroke victims, the mirror box technique can even lead to the recovery of limb function--perhaps by tapping into former mirror neuron circuits that have only been partially damaged by stroke, according to a recent study in the Archives of Physical Medicine and Rehabilitation (Vol. 89, No. 3).

Mirror neurons, those that fire both when a person performs an action and when that person sees an action being performed, may lay the foundation for observational learning, empathy and even humanity's unrivaled ability to make cultural advances, Ramachandran posits. Mirror-neuron dysfunction could even be at the root of autism, according to a study he co-authored for Social Cognitive and Affective Neuroscience (Vol. 2, No. 1).

In this interview, Ramachandran makes a case for bringing more psychologists into the fMRI lab--and basing more brain-imaging work on hypotheses gleaned from cognitive and behavioral findings.

Will neuroscience supplant psychology?

I wouldn't say that. However, neuroscience will make psychology much more scientific, with more predictive power--leading to a deeper understanding of mental phenomena than psychology could achieve on its own.

Psychology has been going on for quite a long period of time, so why does it have this somewhat dismal record answering basic questions about the mind? We don't know, for example ... what is empathy? Psychology has found that you empathize with people you like, and you don't empathize with people you don't like. With neuroscience you can understand it at a deeper level than just describing where and when it happens. Autism may be caused by a lack of these mirror neurons or empathy neurons--which explains a lot of the puzzling symptoms of autism. These kids have trouble with pretend play--they can't pretend to put themselves in someone else's shoes because of a lack of these neurons. They have difficulty with imitation. They lack emotional empathy in social interactions--all symptoms that can be explained in terms of mirror neurons.

When you discover a neural basis, it allows you to explain a whole host of other phenomena that initially seem unrelated. This doesn't eliminate psychology, it complements it.

How might neuroscience help answer psychology's most intractable questions?

Psychology, by itself, has made tremendous strides--in developing an understanding of color vision, for instance. But it has left a lot of simple questions unanswered, like: Why do we sleep? Why do we laugh? Why do we cry?

The problem is that you can have an explanation in biology at two different levels. One is a "black box," or non-reductionist approach. An example of this is behaviorism, which gives you a model of what's going on at the same level as the phenomenon you are studying.

Or you can go one step below and say, What are the component parts and how do they interact to produce these phenomena? The advantage of this approach is that not only does it explain the phenomena you are talking about, it opens up a host of other possible explanations.

In biology, for example, Mendelian genetics--where you have pea plants and genes--could only get you so far. Sooner or later, you need to open it up and see what's inside. You have to discover the structure of the DNA molecule--an advance that gave birth to modern biology, because it told you about enzymes; it told you about ... the machinery underlying cell physiology.

In psychology, the nearest thing to that happening is neuroscience. Through neuroscience, we are going to have explanations, deeper explanations with far-reaching consequences, of phenomena like empathy, self-awareness and language.

What are the major limitations of brain-imaging research?

Thinking is very difficult, and when you have fancy technology, you get the illusion you are making progress: You put someone in a machine and you get some pretty pictures. It's come to the point where, even if you have an experiment with consequences that blow your mind, some journals won't accept it unless you have images.

But I think the opposite is more prevalent: where psychologists are resentful of neuroscience taking over the field. I call this neuron envy. All the new imaging technology is going to revolutionize the field, especially if it is accompanied by intelligent, conceptual hypotheses. You should think, This is what psychologists have discovered about how memory works, so this is what should happen in the brain. Let's see if what we expect plays out at the brain level.

The key is do not go on fishing expeditions. Have specific, testable hypotheses. That's not currently happening; 98 percent of brain imaging is just blindly groping in the dark.