The objective of this issue is to introduce the readers of Ergonomics to the unique benefits of a psychophysiological approach. The collecting of physiological data, of course, is not new to the field of ergonomics. For example, the study of circadian rhythms, energy expenditure, and efficiency of movement involve physiological assessment and are clearly relevant to ergonomics. However, as a scientificc approach, psychophysiology attempts to go beyond the correlational relations between physical and physiological responses and to include the study of physiological indicators of subjective states such as perceived task demand,
alertness and mental effort. Psychophysiology attempts to ask more integrative questions regarding the relations among behavioural, psychological and physiological variables. In addition, psychophysiological
methods and theories emphasize the importance of the nervous
system and how the neural modulation of physiological systems promotes or limits the range of specific behaviours. Thus, within a psychophysiological approach, subjective states such as fatigue and
eOEort may be translated into a measurable neurophysiological substrate that would limit the range of behaviour within the workplace.