Times of our lives by Karen Wright, in the current Scientific American
Adrenaline and other stress hormones make the clock speed up, as do cocaine and meth. Parkinson's patients and dope-smokers have less available dopamine and experience slower time. States of deep concentration or extreme emotion may flood the system or bypass it altogether; in such cases, time may seem to stand still or not exist at all. Because an attentional spike initates the timing process, people with attention deficit hyperactivity disorder might also have problems gauging the true length of intervals.
Circadian rhythms are something else again. "Confined to a petri dish under contassnt lighting, human cells still follow 24-hour cycles of gene activity, hormone secretion and energy procution. The cycles are hardwired and vary by only a few minutes a day!
Most animals have extreme changes throughout the year, for hibernation, molting, and the all-important procreation. We humans get seasonable affective disorder. Big deal.
