Attention was described by William James (1890, cited in Eysenck & Keane, 2000, p.130) as “the taking ownership of the head, in clear and graphic form, of one out of what seem several simultaneously possible objects or trains of thought. Focalization, concentration of consciousness is of its essence.” This definition emphasizes how attention is a selective process. It seems clear from common sense that we cannot attend to all stimuli at once, so some sort of selection must take place as to what information we attend to and process further and what is disregarded. Since the 1950s, there has been a great deal of research into selective attention, both auditory and visual.
Several different theories and models of selective attention have been proposed. One key and ongoing debate in attention research has been that between early and late selection theories, i.e., at what stage of processing a stimulus does selection occur? This essay will compare and contrast early and late selection models of attention.
The main examples used to illustrate similarities and differences will be Broadbent’s (1958) filter theory model (as cited in Driver, 2001), which was the first cognitive model of auditory attention and an extreme example of early selection, and the rival late selection model proposed by Deutsch and Deutsch (1963). It will then move on to evaluate these, along with other models, including Treisman’s (1960, as cited in Driver, 2001) attenuation model, as to how well they are able to explain the phenomenon of selective attention.
Both early and late selection models of selective attention were originally derived from research into auditory attention, attempting to explain how the human auditory system is able to process various dichotic listening experiments that were conducted (Driver, 2001; Naish, 2010).
In this experiment, participants had different messages played into each ear and were asked to shadow, i.e., repeat the message from only one ear. They would then be asked questions about what they remembered from the message that had been played into the other, non-shadowed ear. In most cases, it was found that participants could recall almost nothing about the message in the non-shadowed, i.e., unattended ear (Driver, 2001, p.55).
Driver (2001, p.55) demonstrates how both early and late selection models can be represented as very simple two-phase flow diagrams, illustrating how different early and late models of selective attention all appear to be based on Broadbent’s (1958, as cited in Driver, 2001) original filter theory. Both early and late selection models can be thought of as having a selective filter or bottleneck (McLeod, 2007; Eysenck & Keane, 2000), which extracts the attended information for further processing while filtering out irrelevant (unattended) information. Both types of model assume that initial processing of all stimuli takes place in parallel, prior to the bottleneck filter, after which the selected information is thought to undergo deeper, sequential processing. The main difference between early and late selection models is the position of the bottleneck.
Broadbent’s (1958, as cited in Driver, 2001) model assumes that the bottleneck occurs very early in processing (close to the stimulus end if the model is represented as a flow diagram). It is assumed that only simple physical properties of a stimulus are extracted in the parallel pre-attentive phase prior to filtering. Therefore, the unattended stimulus does not undergo any processing for meaning, but only for simple physical features, such as the location of the speaker or whether the voice was male or female.
These simple physical features are all that can normally be remembered about the unattended message by participants in dichotic hearing undertakings. Broadbent (1954, as cited in Naish, 2010) also discovered that if both messages were really short, participants could retrieve the message from the unattended ear. This led to the premise that there was a centripetal buffer, a really ephemeral memory shop besides known as imitative memory, which could keep on to unattended stuff for merely a few seconds prior to selective filtering (Naish, 2010).
By contrast, late choice theoretical accounts, e.g., Deutsch and Deutsch (1963), topographic point the constriction much nearer to the response terminal of processing. Their theoretical account assumes that all incoming stimulations are automatically processed and analyzed for significance, regardless of whether they are consciously attended to or non, with selective filtering happening merely after significance has been extracted. Late choice theoretical accounts provide a possible account for consequences obtained in some dichotic hearing experiments where processing of unattended stimulations did look to take topographic point.
For illustration, Corteen and Wood (1972, as cited in Naish, 2010) paired electric dazes with certain words so that a learned voltaic tegument response (GSR) took topographic point. Subsequently, when these words were once more presented to the unattended ear (without electric dazes), the GSR still occurred for these words every bit good as other words from the same class, bespeaking that treating for significance had so taken topographic point. Late subdivision theories could besides be used to explicate the cocktail party consequence (Naish, 2010), i.e., if someone is go toing to one conversation at a party and their name is mentioned in another conversation in the room, they are able to hear their name and exchange their attending to the other conversation.
The above illustrations lead us to see some restrictions of a rigorous early choice theoretical account such as Broadbent’s (1958, as cited in Driver, 2001) filter theory. Whilst this theoretical account explains the consequences of early tailing experiments (Driver, 2001), the inflexible nature of Broadbent’s theoretical account means that it cannot to the full account for the cocktail party consequence, or for the findings of a figure of experiments in which changing grades of processing of unattended stimulations are observed to take topographic point.
One such survey was carried out by Treisman (1960, as cited in Driver, 2001) in which she found that while shadowing a message played into one ear, participants would sometimes exchange to shadowing the other, antecedently unattended ear when the message they had been shadowing was switched over. Treisman went on to develop an alternate selective attending theory (Treisman, 1960, as cited in Naish, 2010 & Driver, 2001) which argued that unattended stimulations were not wholly filtered out but turned down or attenuated. Normally, this would make them too weak to be available for semantic processing, but in certain circumstances, e.g., when words from the unattended message had particular significance.
Such as one’s own name or words relevant to the accompanying message, these words would hold a lower threshold for designation and hence would be processed. Treisman’s theoretical account can be considered an early choice 1, as it is fundamentally a modified version of Broadbent’s (1958, as cited in Driver, 2001) filter theoretical account, where the fixed constriction is replaced by a more flexible “attenuator” (Eysenck and Keane, 2000). Treisman’s theoretical account can be used to explain the cocktail party effect as well as the other experimental findings mentioned above. In the study by Corteen and Wood (1972, as cited in Naish, 2010), words associated with electric shocks would probably be very important to the participants; therefore, the threshold would be low enough for identification to occur.
The selective attention models discussed above have all had a great deal of influence in attention research and have certainly been useful in helping our understanding of how certain processes might happen. Broadbent’s filter theory (1958, as cited in Driver, 2001) in particular has been vastly influential, with many subsequent models of selective attention in auditory and visual research being based upon its simple, logical structure. However, it should be noted that in real life, selectively attending to information is a very complex process carried out by the brain and cannot be fully explained by such a simple computational model.
This point has been made by Allport (1980, 1987, 1992, as cited in Driver, 2001) and will be returned to later. There are a number of methodological issues that can be used in criticism of selective attention theories, particularly of Broadbent’s theoretical account (Driver, 2001). One of these is that in early dichotic hearing experiments, participants were unfamiliar with the shadowing task, so it would have placed heavy demands on their processing capacity just to be able to shadow the accompanying message (Eysenck and Keane, 2000). Second, participants in these early experiments were questioned retrospectively about the message played to the unattended ear.
Their studies show that knowing very little about the message could be due to participants having forgotten it, rather than there being no processing of the message at all. This problem was addressed in subsequent research by designing experiments in which indirect measures of processing were used. One example mentioned previously was Corteen and Wood (1972, as cited in Naish, 2010), where GSR was measured, giving results inconsistent with Broadbent’s theory.
Another important methodological issue, and according to McLeod (2007), a problem with all dichotic hearing experiments, is the possibility that participants could simply switch their attention from one channel to the other, leading researchers to falsely conclude that the unattended message was being processed. This point is also emphasized by Lachter, Forster and Ruthruff (2004), who attempted to control for this phenomenon in visual attention experiments, and whose findings support Broadbent’s (1958, as cited in Driver, 2001) filter theory.
Driver’s (2001) review provides many examples of similarities between auditory and visual attention research in terms of the early versus late selection debate. Sperling (1960, as cited in Driver, 2001) found evidence for a very brief short-term memory buffer, which was equivalent to Broadbent’s echoic memory, and termed ‘iconic memory’. Rock and Gutman’s (1981, as cited in Driver, 2001) findings were consistent with early selection models derived from shadowing experiments and were also subject to the same methodological concerns, as they used retrospective questioning to assess whether unattended information had been processed.
Treisman’s (1988, as cited in Driver, 2001) feature integration theory can be said to bear a strong resemblance to Broadbent’s (1958) model. This is illustrated very well by Driver (2001, p.55), where he simplifies it into a two-stage flow diagram consisting of extraction of physical features, followed by integration of features for the selected object. Rival late selection theories include those of Tipper (1985, as cited in Driver, 2001) and various others, as reviewed in Driver (2001), and were based on studies involving negative priming effects, as well as other indirect measures suggesting that unattended stimuli were fully processed.
A possible resolution to the longstanding early versus late selection debate was proposed by Lavie (1995, 2000, as cited in Driver, 2001) in the form of a perceptual load theory, which, based on the assumption that the system had limited capacity, could integrate findings in favor of both early and late selection models.
Lavie conducted an extended reappraisal of the literature, as well as conducting her own experiments, and argued that results supporting late choice were usually obtained in situations of low perceptual burden, for example, an undemanding task involving one target and one distractor. The system would, therefore, have spare capacity for processing non-target information. Conversely, in situations where perceptual burden is higher, as in more difficult target identification tasks, an early choice account tended to be more appropriate, as little or no spare capacity would be available. Evidence from neuroscience should also be considered in this evaluation.
Woldorff et al. (1993, as cited in Naish, 2010) recorded data from event-related potentials (ERPs) in the brain following auditory stimulation. The results provided very strong evidence in support of both early choice and fading; attending away from a stimulation reduced the strength of the signal in the brain. Driver (2001), who was once in favor of late choice, now argues that late choice has been definitively falsified by evidence from neuroscience. Driver (2001) also reviews further evidence from neuroscience, which reminds us that attention is a complex process involving different brain areas and top-down, as well as bottom-up processes; hence it cannot be adequately represented by simple box flow diagrams.
In conclusion, it can be argued, on the basis of the evidence presented in the above discussion, that an early choice model provides a better explanation of the way in which we attend to information than a late choice one. As there is evidence for fading, perhaps Treisman’s (1960, as cited in Driver, 2001) fading theory is more appropriate than Broadbent’s (1958, as cited in Driver, 2001) theory. Finally, it must be restated that attention is a very complex set of processes and cannot be fully explained by any of the simple models discussed here; however, they have been very useful in aiding our understanding.
