Bio-feedback devices allow individuals to train on control an aspect of their autonomic physiology. Autonomic, in other words, means automated and controlled by lower brain functions and therefore not under out conscious control. This belief, however, is outdated – it proved to be a fallacy. Training a person to control such physiology as EED (brain waves), EKG (heart rate), blood pressure, and tension level proved to be possible once a method became established of showing a person (feedback) the physiological changes they are trying to control in real time.
It is interesting that the control of these functions cannot be accurately taught verbally. It is the training or the conditioning of the body using a bio-feedback device to feel a particular way or to get a feeling that controls these functions.
The types of bio-feedback devices available are numerous. The type that we will build in this chapter is a galvanic skin resistance bio-feedback device, see Figure 1. Galvanic skin resistance is a good indicator of stress level in the subject. But perhaps its most famous attribute is its use as a lie detector.