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Compare and contrast early vs late selection models of attention essay

Specifically, it is concerned with some of the theories that have attempted to explain attention by using ideas from information processing theory. Of the most influential theories in the field, the majority fall into two broad categories: Although, the latter are arguably the most favoured nowadays, it is the former which we shall concentrate upon, since they have probably been the most influential.

It is worth noting at the outset that both bottleneck and capacity theories are based on the idea that humans have limited information processing capacity: Capacity models, on the other hand, are a weaker version, in that information can be processed via many channels but that there is a fixed capacity limit to be distributed amongst the channels. Before launching into a detailed analysis of the three most influential bottleneck theories which emerged in the late 1950s and early 1960s, it would be helpful to establish a perspective from which to make the comparison.

As a start, therefore, it does not seem unreasonable to ask a fundamental question: Without a good idea of what attention is, and especially its relationship to perception and consciousness, we are in a poor position compare and contrast early vs late selection models of attention essay compare theories.

A very early definition recently described as an "elegant summary"; Underwood, 1993 is that of William James over 100 years ago: Focalization, concentration of consciousness are of its essence. It implies withdrawal from some things in order to deal effectively with others" James, 1890. James's definition neatly exposes a problem that dogs the field of attention: Dixon 1981 is almost a lone voice in squarely confronting this issue, noting that one legacy of behaviourism is that the conscious mind is virtually a taboo subject.

Add to this the idea that the effects of attention are largely preconscious, hence dangerously close to the 'unconscious' of psychoanalytic theory, and one has a double taboo whammy that makes many uneasy and obscures much that is important and interesting. One outcome of this unease is the varying ways in which researchers in the field conceptualise 'attention' and 'consciousness', often doing so in order to skirt around some of the fundamental problems just described.

Some theorists have made an explicit differentiation between attention and consciousness. For example, Johnston and Heinz 1968 view attention as "the systematic admission of perceptual data into consciousness. This seems a compelling idea, and especially fits with the bottleneck theories of selective attention, unfortunately there are some problems with it.

Firstly, there is the problem that attention seems sometimes to be under conscious volition and at other times often annoyingly not. This raises the key question: A second problem is that the view of attention as a kind of selection process before ideas are allowed into consciousness where, presumably, most high level semantic processing, planning and decision making is performed does not fit with certain empirical findings, especially in the field of subliminal perception.

If we ally this to the popular view of attention as "the concentration and focusing of mental effort Matlin, 1983 ", then we have a notion of attention which can be quite separate to consciousness.

In other words, if attention is a concentration of mental effort, and mental effort can be exerted unconsciously, then attention, at least in part, acts separately to consciousness. As an alternative, attention can be viewed in the highly restrictive sense of only being necessary for information that is novel and important.

This introduces the ideas of acquisition of skill and automaticity which are performed without conscious control which Reason, 1979, calls open loop control. As we shall see later, this has important implications for the efficacy of the ubiquitous dichotic listening paradigm.

Treisman 1988 takes this view, seeing attention as being necessary for the integration of perceptual features that form objects i. The third problem with the Johnston and Heinz definition is more practical, in that not everybody has adopted it e. Best's definition just presented. This may seem an obvious point, but introduces an important and often overlooked idea: It is all too easy to impose one's own conceptualisations on certain words e.

It is as if one were to compare and contrast a Jackson Pollock with a Raphael on one's own notions of "beauty", "meaning" and "harmony". Theories of Attention From issues associated with a defintion of "attention", let me now move on to compare the clearest and the most influential bottleneck theories of selective attention: At a basic level, these theories appear to explicitly show that the locus of the bottleneck in a person's information processing system is either 'early' perceptual limitations or 'late' response limitations.

We shall see later that this may be too crude an assessment, and shall also briefly consider other possibilities that arise from the work of Johnson and his colleagues which have been seen as resolving this 'early' verses 'late' problem. For both historic and conceptual reasons, the easiest way to start a comparison of the three theories is to look at them in two pairs: Comparing Broadbent's and Treisman's theories Comparing Broadbent's and Treisman's theories is a relatively straightforward affair since Treisman's model is a direct amendment of Broadbent's.

Let me firstly give an brief outline of each model. Incoming stimuli, briefly held in a sensory register, undergo preattentive analysis by a selective filter on the basis of their physical characteristics. Those stimuli selected pass along a very limited capacity channel to a detection device where semantic analysis takes place.

Those stimuli not selected 'filtered' out are not analysed for meaning and do not reach consciousness.

This is, therefore, an early selection theory, and an 'all or nothing' view of perception. Incoming stimuli, briefly held in a sensory register, undergo preattentive analysis by an attenuation filter on the basis of crude physical characteristics the information resulting from this analysis is compare and contrast early vs late selection models of attention essay to conscious perception and for reporting by the subject, regardless of what happens to the message beyond this point.

Those stimuli selected attended to pass along a limited capacity channel to a detection device a pattern recognizer, comprising a number of 'dictionary' units where semantic analysis takes place. Unattended stimuli are attenuated the signal strength is lowered before passing along the limited capacity channel to the detection device, where they are semantically processed if they meet certain criteria.

This is, therefore, an early selection theory, and an attenuation model of attention.

These theories have far more ideas in common than they do differences, yet it is the differences which are the key aspects. The two major differences are outlined in the following two paragraphs. Broadbent's filter is all-or-nothing it does not allow through unattended messageswhereas Treisman's filter allows unattended messages through, but in an attenuated form. Treisman proposed this amendment to account for a number of empirical findings which were not explained by Broadbent.

For instance, Moray 1959 had found that "subjectively 'important' messages such as a person's own name can penetrate the block [the all-or-nothing filter]: A similar finding by Oswald et al 1960 found that a person's own name and critical names presented to a sleeping subject elicited a clench response which had been previously conditioned.

Treisman 1960using a dichotic listening with shadowing procedure, found that if different sentences in the two ears are suddenly switched, then the subject shadows one or two words of the unattended message before reverting back to shadow the attended ear. Clearly, certain unattended messages can be processed semantically, hence the need to modify the physical characteristics filter.

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Broadbent's is a simple single filter model, whereas Treisman's can be thought of as a two-stage filtering process: Treisman's explanation as to the way these threshold settings perform a filtering operation explains the findings of Moray, Oswald and Treisman described above, and many other similar findings. The dictionary units have the two mportant properties of having thresholds that differ, and which are variable. Some units, those which respond to biologically or emotionally important signals, have permanently lowered thresholds.

Hence, even very attenuated signals because they are not being attended to can trigger a unit which is 'tuned' to that signal. This explains the reason why one's own name can attract one's attention in a previously unattended message. On a more biological level, this explains the sensitivity that mothers have for the noises their babies make, even when virtually out of earshot. In addition to these semi-permanent threshold differentials, there is the transient variation in thresholds due to the expectations of the subject i.

The occurrence of a particular signal will, if it triggers a dictionary unit, lower the threshold for other signals which in the past have been associated with it.

Hence, highly probably words e. Comparing Treisman's model and Deutsch and Deutsch's model Let us move on to a more problematical task: There are two key points to consider.

Firstly, Deutsch and Deutsch's theory is based on the same empirical data as Treisman's theory, but is reinterpreted from a different perspective.

Secondly, Deutsch and Deutsch saw Treisman's model as being flawed in that the dual filtering process is redundant - why have the lower level filter, if the same job can be done by suitably controlling the thresholds of the dictionary units?

Let me briefly outline Deutsch and Deutsch's theory. Almost every incoming message in a sensory register reaches "the same perceptual and discriminatory mechanisms whether attention is paid to it or not; and such information is then grouped or segregated by these mechanisms". Discriminatory or classifying mechanisms become excited by particular attributes of the incoming message depending on preset weightings of importance.

The discriminatory mechanism with the highest weighting will transfer this weighting to the other classifying mechanisms with which it has been grouped or segregated.

Since there will normally be activity in a number of classifying mechanisms, a "diffuse and non-specific system is necessary" which takes up a level, at any one time, corresponding with the level of the 'highest' discriminatory mechanism. This highest level sets a criterion by which all other levels are compared.

Hence, only the discriminatory mechanism with the highest level activates the appropriate outputs storage, motor response and inhibits the outputs associated with the other discriminatory mechanisms.

Further, the general level of arousal will alter access output systems.

Discuss the validity of early and late selection models of attention.

Hence, for a low level of arousal e. At first sight, and accounting for major differences in terminology, this looks very similar to Treisman's theory. The 'discriminatory mechanisms' with their 'weightings of importance' look remarkably similar to Treisman's 'dictionary units' and 'thresholds'. One obvious difference is that Deutsch and Deutsch have no low level physical characteristics filter.

Another difference is that all the 'discriminatory mechanisms' including physical compare and contrast early vs late selection models of attention essay semantic classifying structures in Deutsch and Deutsch's theory are triggered, whereas Treisman has only those 'dictionary units' with signals above a threshold being triggered. However, since Deutsch and Deutsch have only the highest level being capable of further processing output responsethis amounts to the same idea as Treisman, whose threshold settings are altered depending on those units being triggered.

So what is all the fuss about? The question then is: Why is Treisman's theory seen as typifying 'early' selection and Deutsch and Deutsch's as typifying 'late' selection? Support for the idea that both theories are basically the same comes from Moray page 35, 1969 who in reviewing early and late selection theories, quotes a personal communication with J. Deutsch in 1968, in which: So why this misinterpretation in analysing the two theories.

I believe the problem stems from the fact that the two theories come from different areas of psychology, and consequently are couched in the different language and conceptualisations. Treisman is wholeheartedly a cognitive psychologist using the tricks of the trade dichotic listening, shadowing, reaction times, memory tests to tease out the way different units in the mind process information.

Deutsch and Deutsch, on the other hand, are from the biological school and I believe have never touched a pair of dichotic listening headphones in their lives.

To use an artificial intelligence analogy, one could say that Treisman favours a traditional serial processing approach, whereas Deutsch and Deutsch are from the connectionist school of parallel distributed processing and neural networks.

The difference is highlighted when one reads their original papers. Whereas Treisman is written in "information processing speak", Deutsch and Deutsch's language is in terms of organisms, behaviours and neurophysiology in fact their original paper contains a substantial section on the neurophysiological evidence relevant to their ideas. It is an astonishing, and little known, fact that Deutsch and Deutsch original 1963 paper on attention contains neither the word "consciousness" nor the word "conscious".

In the first, "Selective attention: In the second paper, "Comments on 'Selective attention: To add insult to injury, Deutsch and Deutsch go on to criticise Treisman's amendment of Broadbent's theory, by arguing that the reduced signal-to-noise ratio of unattended messages rather than reducing the load on the signal-recognition system would actually increase it, since signal detection theory says that the noisier the signal, the more analysis is required to extract it.

No doubt Treisman, Deutsch and Deutsch are highly intelligent and knowledgeable people, and it is not my place to try and resolve their differences.