by Winafred B. Lucas, Ph.D.
The effort to document physiological correlates of inner states is relatively recent. It began with three biofeedback instruments: the temperature meter, the OSE, which measures stress and relaxation through skin resistance; and a simple electroencephalogram. (The first electroencephalographic recordings picked up only one brain wave pattern at a time—the dominant one—and for a while it was not clear that the brain actually produced waves on different levels at the same time). Gradually various feedback devices made it possible to measure and record bodily changes that before that time had been considered unavailable to consciousness. Their measurement and recording opened the door to an expanded understanding of physiological self-control.