Over the past several years, there has been significant research in determining the state of the brain during hypnosis, including proving the difference between hypnosis and sleep.
Now, this study from reported in New Scientist and referenced here at Io9, describes a physical sign that a person is in a state of hypnosis, and, of course, it happens to involve the eyes. In hypnosis, according to this research, people have different eye reactions, including blink rates and pupil response, things that are impossible to fake or duplicate, things that are caused by changes in the brain activity under hypnosis.
"We found that during hypnosis, the frontal area was almost perfectly disconnected from the rest of the brain," says Kallio. "There are usually lots of connections but during hypnosis they were almost gone."
More than just an additional proof that hypnosis does exist, it also confirms the stereotype of the blank-eyed subject. The old saying "The eyes are windows to the soul" also comes to mind here.