The study of human attention may be divided into three components. These are alertness, selectivity, and processing capacity. This paper outlines experimental techniques designed to separate these components and examine their interrelations within comparable tasks. It is shown that a stimulus may be used to increase alertness for processing all external information, to improve selection of particular stimuli, or to do both simultaneously. Development of alertness and selectivity are separable, but they may go on together without interference. Moreover, encoding a stimulus may proceed without producing interference with other signals. Thus, the contact between an external stimulus and its representation in memory does not appear to require processing capacity. Limited capacity results are obtained when mental operations such as response selection or rehearsal must be performed on the encoded information.

Components of attention

Components of attention.

Temporal information is essential for effective perception and action in the dynamic environment in which we exist. However, our ability to use information about time intervals flexibly to direct attention to an expected point in time has until recently been unexplored. Here we report a series of behavioural, neuroimaging and electrophysiological experiments that investigate and define the ability to orient attention in the temporal domain. These studies reveal that we are able to orient attention selectively to different time intervals, enhancing behavioural performance. These effects are mediated by a left-hemisphere dominant frontal-parietal system, which partially overlaps with the networks involved in spatial orienting. The optimisation of behaviour by temporal orienting appears to be achieved via motor-related mechanisms, in contrast to the typical perceptual enhancements produced by spatial attention. From a more general perspective, these findings illustrate the flexibility of attentional functions in the human brain.

Orienting attention in time.

This chapter1 surveys some current experimental evidence regarding the neurophysiological basis of habituation and attention in the auditory system. The principal focus is upon electrophysiological studies in man although a number of relevant animal studies will also be reviewed.

E. Haines

Papers

Evoked response correlates of expectancy during vigilance.