 Difficult to measure consciousness.  A state of consciousness is referred to as a hypothetical construct.  I.e., a concept used to describe something that is believed to exist, but that cannot be directly observed or measured.  Psychologists infer what they know about an individual’s SOC from information provided to them, behaviour that is demonstrated of physiological changes that can be measured.

 EEG  Brain wave patterns can vary in frequency.  High frequency = more brain waves.  Low frequency = fewer brain waves.  Brain waves can also vary in amplitude.  High amplitude = bigger peaks and troughs.  Low amplitude = smaller peaks and troughs.  4 different brain wave patterns: › Beta, alpha, theta, delta.  Each has a different combo of frequency and amplitude, indicating different kinds of brain activity.

Beta : high frequency, low amplitude. Alpha : high frequency (but lower than beta), low amplitude (but larger than beta). Theta : medium frequency, and mixture of high and low amplitude waves. Delta : low frequency and highest amplitude.

 In some ASCs, heart rate increases from that recorded in normal waking consciousness and in others, decreases.  E.g, while meditating, heart rate tends to decrease or when using a substance, increases.

 Body temp is less variable than heart rate.  General pattern identified indicating that body temperature changes with some ASCs (most predictable during sleep).  Body temp decreases by 1oC when sleeping.

 GSR: a physiological response that indicates the change in the resistance of the skin to an electrical current.  Electrodes attached to sides of a finger or palm of a hand.  Electrodes enabled detection and measurement of how easily the electrical current passes through the skin.  Changes in GSR are closely associated with emotional experiences.  High emotional arousal = increased sweating = increased electrical conductivity.

 Measures of physiological responses can provide useful information about an individual’s SOC, BUT can be misleading if used as the only indicator.  Changes in physiological responses occur for many reasons.  Therefore, they are used in conjunction with observations and self-reports from individuals to obtain more accurate information.