ABSTRACT
In a very influential article, Lindsley (1960) described patterns of EEG activity produced across behavioral states ranging from deep sleep to high alertness. Table 5.1 is adapted from Lindsley and shows his conception of a behavioral continuum, its characteristic EEG waves, associated states of awareness, and corresponding behavioral efficiency. Lindsley attributed an important role to the ascending reticular activating system (ARAS) in regulating states of attention, consciousness, sleep, and wakefulness. The functions of the ARAS also play a part in activation theory that describes the relation between levels of physiological activity and performance (see chap. 2). In 1960, Lindsley wrote:
Attention is closely allied to arousal and wakefulness and, like wakefulness and consciousness, appears to be a graded phenomenon extending from general alerting, as in the orienting reflex, to specific alerting, as when attention is focused upon a given sense mode and dominates sensory input to the point of exclusion of other sense modes. Still higher or more finely focused attention may be restricted to a limited aspect of a given sense mode. (p. 1589)
This description of attention in general and specific form serves as a model for contemporary psychophysiologists in the context of activation theory, which considers the relationship between physiological arousal and performance (chap. 2). However, also of relevance is the Lacey’s theory of stimulus intake and directional fractionation (also see chapter 2). Recall that, in the Laceys’ formulation, there were decreases in some physiological activities (e.g., heart rate) and increases in others (directional fractionation) as people paid attention to stimuli. Thus, Lindsley’s definition of attention fits the view of an activation theory in which there is a continuum of arousal, from very low to very high, with greater degrees of arousal related to more efficient stimulus processing, up to a point, after which further arousal leads to a downturn in performance. However, the Laceys pointed out that there are times when a unitary system of arousal does not describe the data because of situations where one physiological system increases in activity and another shows a decline. This is the situation they described as directional fractionation (see chap. 2).
