Manifestations of Attention

The three major goals of attention listed here are indicative of the ways that atten-tional processing is observed or inferred in behavioral and cognitive situations. When a judgment of an object in a field cluttered with salient objects is made correctly, or one of a set of alternative responses is chosen, it is inferred that selective attention has successfully removed or attenuated the influence of the extraneous and confusing information. For example, identifying the center letter in the word COG requires that information arising from the locations near the center letter be prevented from entering the module (or sets of modules) that performs a judgment of identification. If selection by location does not occur, the entire word COG will presumably enter the identification module and be identified instead of the letter O. On the action side of cognition, selection of information from working memory is assumed to occur when pressing a particular function key on a computer keyboard when other keys are available, and during speaking when a particular word is chosen from alternative words as we pause before emphasizing a point. This manifestation of attention, then, may be referred to as simple selection.

When we observe a substantial increase in speed of responding to the onset of a given stimulus following the presentation of a predictive cue, it is inferred that attention has been concentrated prior to the onset of the stimulus on some processing module or area in the pathways between perception of the stimulus and evocation of the response. Modules that have been shown to be sensitive to predictive cuing are perception of the stimulus (as in cuing the location, color, and shape of an object), response generation (as in cuing a particular response), and working memory (as in cuing a word in a lexical decision task).The resulting effect of directing attention to a processing module is presumed to be a shortening of the time to process the appropriate information at the time when target stimulus information arrives at that module.

James (1890) described the latter case as "preprocessing" of the stimulus, and used it as a prototypical example of attentional "anticipation" or "preparation." In this chapter, this particular manifestation of attention will be denoted as preparation.

It should be noted that preparatory attention is usually directed to a particular feature of a stimulus, or to a particular response unit, or to a particular intervening operation, so that selective processing is required for this manifestation of attention as well as for the simple selection manifestation. However, it is the prolonged aspect of preparatory attention that marks it off from simple selective attention, which can be initiated quickly and without preparation, as in examining successive objects during search.

Preparation to process a stimulus, response, or mental operation almost always involves an expectation of an upcoming time at which the prepared-for processing is to be initiated. This temporal expectation is presumed to be represented in working memory along with a representation of the stimulus attribute or action plan that is to receive preparatory attention. For example, if we are preparing to see a green light flash at a street intersection, we not only have in working memory an expectation of when the light will occur, but we also have in working memory some representation of the green light, perhaps in verbal form. However, preparatory attention requires that an additional step be taken, which is that the representation of the green light in working memory must command a perceptual preparation for the green light, and/or command a motor preparation for pressing the gas pedal. Hence, when a person prepares for a particular type of processing, (from either external or internal instructions), it may not be clear to the person or to an observer whether the preparation is represented only abstractly in working memory as an expectation or is represented also as a preparatory state of the processing component itself. When instructions induce preparation at the site of the processing component, one expects faster processing than when instructions only induce a storage in working memory of the expected perception or action plan.

A third manifestation of the attention process corresponds closely to the third goal of attention considered here, which is the simple maintenance of processing without an accompanying expectation of an upcoming event. Inferring the presence of this particular manifestation of attention is more difficult than inferring the presence of preparatory or selective attention.

However, from the point of view of introspective experience of one's own atten-tional states, maintenance attention would appear to be as directly observable as are the attentional processes of preparation or selection. Other kinds of measurement methods available to the cognitive scientist, such as brain imaging by PET, fMRI, and electroencephalogram (EEG) could presumably provide more objective bases for inferring maintenance attention. However, currently the most effective methods of brain imaging are based on subtraction of measurements across carefully constructed behavioral tasks, which almost always involve specific behavioral goals.

As was the case for preparatory attention, maintenance attention almost always requires selection among items in sensory and memory sources. It appears then that selective processing is a property that unifies all three manifestations of attention.

The three manifestations of attention, selection, preparation, and maintenance, all apparently occur within a trial of a typical behavioral-cognitive experiment. An illustrative example of these manifestations is a trial of the word association task, in which a word is presented and the subject is required to generate the opposite of the stimulus word. Prior to the stimulus the subject's attention is manifest as preparation for perceiving a visual word in a particular location on a screen, and preparation for making a spoken response. as well as a preparation to process the stimulus word as an opposite. When the stimulus word is presented, the subject selects from a set of stored alternative associates, which involves a relatively brief operation of simple selective attention, and emits a verbal response. The response is then evaluated as to its appropriateness and feedback is given explicitly or implicitly. The subject then may shift attention to contemplate the feedback or to process his or her "feelings about the feedback" in the maintenance mode of attention.

Of the three manifestations of attention considered here, two of them, selection and preparation, seem to have been studied experimentally more than maintenance (for a review, see LaBerge, 1995b). This state of affairs may not seem surprising owing to the difficulty of measuring maintenance attention using the typical form of a laboratory task. In his famous chapter on attention,William James (1890) described the "two physiological" processes of attention as "the accommodation or adjustment of the sensory organs" and "the anticipatory preparation from within the ideational centers concerned with the object to which the attention is paid" (Vol. 1, p. 434). Moray (1959) listed selection and concentration (mental set) as the two different aspects of attention, and Posner and Boies (1971) listed alertness (general preparation) and selectivity along with processing capacity as the three components of attention. More recently Posner and Petersen (1990) described three major functions of attention as: (1) orienting to sensory events; (2) detecting signals for focal (conscious) processing, and (3) the maintenance of a vigilant or alert state.

C. Problems To Be Solved by Attentional Processing

In order to achieve the goals just described, attention must be able to restrict the processing of the enormous array of information that is continuously available from sensory and memory sources. Ambiguous and extraneous information can lead not only to inaccurate responses, but also can lengthen the time to respond. This problem exists not only for the system regarded as a whole, but also for particular modules that participate in cognitive processing, such as modules that specialize in processing location information and shape information on the stimulus side, and modules that specialize in configuring external and internal actions on the response side.

Another problem for attention to solve is to prolong the selection of information in the sensory and memory arrays until a particular anticipated action or event occurs, or simply for its own sake without anticipating some future action or event. But under some circumstances sustained attention may be counter-adaptive, as in the example of the animal attending exclusively to eating while being stalked by a predator. Therefore, to be adaptive, the attentional processes must be subject to interrupts. An interrupt may be regarded as prioritizing attentional selection toward a particular class of events. The clearest examples of interrupts are sudden changes in luminance or sound produced by the abrupt appearance of objects (Yantis, 1993; Yantis & Jonides, 1990), which frequently signal highly significant events in the daily life of animals and humans. An object that signals its presence by an abrupt onset may subsequently become the target of sustained attention, but then attention to this object in turn becomes vulnerable to interruption by sudden changes in the sights and sounds of still other objects.

The three problems just described, restricting of processing to specific inputs, prolonging this restriction, and interrupting such restrictions, do not exhaust the hurdles that confront an attention process if it is to do its job and be an effective part of the processing system, but they would appear to be among the major ones. Other problems for attention are prompt termination of selective processing of one object once an appropriate judgment has been made (e.g., with respect to its identity or color); rapid shifts to selectively process another object, preferably an object that has not yet been scanned, as apparently occurs in rapid search and in rapid, fluent reading; and rapid shifts between two or more tasks that require simultaneous monitoring.

D. Summary of the Present Cognitive Neuroscience Framework for Understanding the Attention Process

This initial section of the chapter provides a framework for inquiry into the attention process by combining concepts and methods of the cognitive science disciplines of cognitive psychology and neurobiology. The first question deals with the goals of the individual's processing system that are met by attention, and the second question deals with the set of problems to be solved by attentional operations if they are to benefit the life of the individual. Three goals of the attention process were stated: accurate and fast judgments of objects and ideas and the sustaining of desired mental processing. Attention was said to meet these three goals with three corresponding manifestations of attention: simple selection, preparation, and maintenance. Common to all three manifestations of attention is the selective property, but the duration of selection is typically more prolonged in the manifestations of attentional preparation and attentional maintenance.

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