Evaluate critically the evidence in favour of late selection.

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Shikha Gosain

Evaluate critically the evidence in favour of late selection

The debate concerning the locus of attentional selection has been a moot point ever since Deutsch and Deutsch (1963) contested Broadbent’s theory of early perceptual selection with their theory of late response selection (1958). The production of competing data and competing explanations over whether selection occurs early or late has been relatively unsuccessful in facilitating our understanding of attention. However, it has become increasingly apparent that the degree of processing achieved by information in visual displays is dependent on a variety of factors and, therefore, a clear-cut distinction between early selection and late selection may be inappropriate. In particular Miller (1991) identified that the processing of unattended stimuli depended on how much of the attentional capacity was engaged by the attended items. This concept was investigated further by Lavie (1995) who reviewed evidence for the effect of load (number of items) on performance in a variety of selective tasks. Lavie (1995) proposed that whether attention is early or late depends on the demands of the task. Lavie’s work directs us to a promising compromise between a strict early or late selection theory. This essay will firstly outline the main principles of the early selection and late selection theories. Evidence for late selection will then be presented and evaluated in terms of the demands of the experimental tasks employed and it will be demonstrated that overall the results obtained under low perceptual load will be consistent with late selection. Contrasts with evidence for early selection will also be discussed where appropriate.

The early selection approach claims that visual perception is capacity limited and therefore requires early attentional selection in order to proceed. In this case, rudimentary characteristics such as physical features are used to distinguish selected items from non-selected items and unattended stimuli are considered unperceived. Although the early-selection approach has warranted a great deal of empirical support, automatic processes have become the focus of attention theories. It is automatic perception that underpins the late selection theory, which states that visual perception occurs in parallel regardless of attention. According to this theory, selection occurs late in the process and allows for full perception of all the stimuli before a relevant response is provided.

In order to directly address the issue of the locus of selection, irrelevant processing needs to be assessed and indirect measures of unattended processing are typically used to gain support for late selection. The Stroop task (Stroop, 1935) is thought to provide direct evidence for late selection. Stroop found that when the name of a colour is written in an incongruent ink colour, subjects are slower to read the word than when the ink colour does not conflict with the colour represented by the word or when the word is not the name of a colour. This demonstrates that the ability to respond selectively to one aspect of the Stroop stimulus is interfered with by the other aspect. It is thought that subjects cannot avoid processing the meaning of the word when responding to its colour and the word automatically activates its response. Although conscious control can prevent the response from being made overtly, there is a time cost while the intended response, ink naming, gains control of overt action. In this way the Stroop effect has generally been interpreted as an indication of parallel processing of the relevant and irrelevant dimensions which is an inherent part of late selection.

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According to Lavie (1994) the parallel processing that occurs in the Stroop task is attributable to the fact that the task is characterized by an especially low level of perceptual load as well as poor physical distinction between the relevant and irrelevant stimuli. Lavie claims that early selection requires the perceptual load of the task to be sufficiently high to exceed the upper limit of available resources in addition to a clear physical distinction between relevant and irrelevant information. Therefore, the Stroop task does not allow the failure of the early selection process to be attributed to either the ...

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