In the heart of consciousness is subjectivity, this sense of having a self that observes one's own organism and the world around that organism. That is really the heart of consciousness.

When you deal with something like compassion for physical pain, which we know is very, very old in evolution - we can find evidence for it in nonhuman species - the brain processes it at a faster speed. Compassion for mental pain took many seconds longer.

When we talk about emotion, we really talk about a collection of behaviors that are produced by the brain. You can look at a person in the throes of an emotion and observe changes in the face, in the body posture, in the coloration of the skin and so on.

There's that effect that is very physical, very down there at the synaptic level, which really means microscopic cellular level, but also molecular level, because all of those structures are operating on an electrochemical basis and so the changes there are very important.

When you experience the emotion of sadness, there will be changes in facial expression, and your body will be closed in, withdrawn. There are also changes in your heart, your guts: they slow down. And there are hormonal changes.

The autobiographical self has prompted extended memory, reasoning, imagination, creativity and language. And out of that came the instruments of culture - religions, justice, trade, the arts, science, technology.

We're seeing it the same way, we're hearing the same way, we have the same conception of the situation. And so, for all purposes, we are operating with a very similar perception.