Individuals who rate high on the so-called Anxiety Sensitivity Index, or ASI, have a high degree of what's known as interoceptive awareness, meaning they are highly attuned to the inner workings on their bodies, to the beepings and bleatings, the blips and burps, of their physiologies; they are more conscious of their heart rate, blood pressure, digestive burblings, and so forth than other people are.

To some people, I may seem calm. But if you could peer beneath the surface, you would see that I'm like a duck--paddling, paddling, paddling.