Operator Effort and the Measurement of Heart-Rate Variability

This paper discusses the usefulness of heart-rate variability (sinus arrhythmia) as an index of operator effort. Effort is involved if task performance requires the use of attention-demanding, controlled processing. This form of processing heavily uses a capacity-limited mechanism: working memory. Effort is also required if the current state of the subject deviates from the target or task optimal state because of fatigue, circadian rhythm, time of day, sleep deprivation, time on task, drugs, heat, or noise. Effort is involved whenever an attempt to resolve mismatch of target and current state takes the form of active manipulation of cognitive resources. We argue that spectral analysis of sinus arrhythmia is useful to obtain more insight into the physiological mechanisms that underlie heart-rate variability. In the present study, it is shown that the amplitude of the 0.10-Hz component of this signal systematically decreases as the load on working memory increases. Some suggestions are made to apply the methods and techniques discussed in this investigation.