Attentional capacity is a common feature of models of attention; critically evaluate the use of this concept in models such as Kahneman (1973)

Attentional capacity is a common feature of theoretical models of attention; critically evaluate the use of this concept in models such as Kahneman (1973).

“It is the taking possession in the mind, in clean and vivid form, of one out of several simultaneous possible objects or trains of thought. Focalization, concentration of consciousness are of its essence. It implies withdrawal from some things in order to deal effectively with others”. Attention as defined by James (1890, pp 403-404).

James’ definition encompasses the numerous cognitions involved in attention. It can be the selection of a single focal interest to attend to or a number of things all going on at once. It involves the brain managing and allocating these functions to maximum efficiency, both consciously and without conscious awareness. It is a definition that holds to a paradigm that has led theory production since; the concept of attentional capacity. Is attentional capacity limited so we can only attend to one thing at a time or can we deal with several things at once? Do we necessarily have to select some things and withdraw from others, and if so, on what criteria? Two main schools of though have arisen that view attentional capacity as fixed or flexible.

Young and Stanton (1997) believe that selective attention models have focussed on the idea that the brain is a limited capacity processor. This paradigm is based upon the posit that if the demands are greater than the resources allocated to deal with it, then performance decreases. Implicit in this notion is the concept of a filter, which at some point in processing selects or deselects information incoming from the senses. The selected information undergoes processing and an output response in the form of behaviour occurs. There have been many models of attention each of which places this theoretical filter at various places in the information processing model and these have been categorised as either early or late selection according to the location of the filter. Broadbent (1958) places the filter early in the process where it deselects all but the consciously attended to information, Treisman’s model (1960) is similar but allows the filter to send through some unattended information in an attenuated form, and Deutsch and Deutsch (1963) propose a model where the filter is much later in the process and depends on factors such as salience.

However, early serial processing ‘bottleneck’ models are not without problems. In order for a theory to be adequate it must explain observable behaviour. Broadbent’s model is not supported by studies such as Gray and Wedderburn’s (1960) fractured digit experiments that demonstrate that participants can recall words that the experimenter believes them to not have attended to. Treisman’s model proposes that attentional capacity is limited as less important stimulus inputs are attenuated according to the demands of the task. However, if this is the case, how can we explain multi-tasking? Deutsch and Deutsch (1963) developed a model where the filter is later in the flow of processing as is based on salience, but it is argued that this is an uneconomical model.

The everyday experience of attention leads towards a more parallel processing approach as we can automate some functions and even perform several functions at once. Clinical studies of agnosic patients (Habekost and Rostrup, 2006) and tachistoscope experiments (Sperry, 1968) also demonstrate that attention can be below consciousness. Case studies of people with Savantism show that their attentional capacity seems to be way beyond the norm allowing them to perform incredible feats of memory. So, could we all possess some of this enhanced mental capacity but that it just untapped? (Snyder, Mulcahy, Taylor, Mitchell, Sachdev and Gandevia, 2003). It is possible that only a fraction of attention is conscious (Von Wright, Anderton and Stenman, 1975.) The implications of this are that the capacity is greater than thought, as conscious attention is only the ‘tip of the iceberg’.

Kahneman (1973) proposes a more fluid model of attention based on the assumption attentional capacity is not fixed. This challenges the notion of attention dependent upon a single limited capacity processor. The model suggests that attentional capacity increases (or decreases) in response to arousal levels, the task, individual differences in disposition, and momentary intentions. This process is subject to an evaluation and assignation factor to allocate resources thus suggesting that processing is parallel. Experience and experimental studies show that attentional capacity can permit multi-tasking as long as the task demands do not exceed the available appropriate cognitive ...

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Many of the limited capacity models are based on dichotic listening experiments. Participants are told to attend to inputs to one ear and shadow the message. As they have to repeat the message it is assumed that it would be too effortful to switch over to listen to the unattended ear. However, Mowbray (1964) claimed that shifts in attention to the unattended channel could easily be possible and that this is what accounts for the reports of inputs from the unattended channel. Kahneman’s model would predict that attention can be constantly assigned and reassigned and this is borne out by fractured digit experiments. The results from dichotic listening studies rely on self-reports from participants that could be subject to inaccuracies. Models of attention have to rely on implied processes and inferences from the response from participants. Additionally, it is very difficult to adequately conceptualise the processes involved in attention using a simple information-processing model, as the multiple complexities of cognition cannot be seen.

Sperry (1968) performed visual attention studies with comissurotomy patients and participants whose corpus callosum was still intact. These demonstrated that attention is often unconscious and importantly that function is lateralized asymmetrically, possibly with each hemisphere having its own conscious attention and perception of events. Some of the results from the dichotic listening studies could have been due to differences in lateralization of function and also which ear the message was presented to. Individual differences between participants may result in variations in lateralization according to Clements, Rimrodt, Abel, Blankner, Mostofsky, Pekar, Denckla, and Cutting (2006). So the results from dichotic listening experiments (and limited capacity theories from which they were built) could have been skewed by these factors. Kahneman’s model predicts that attentional capacity is subject to individual differences and thus processing uses the available resource resulting in variations in capacities across participants.

Developments in cognitive neuropsychology and the use of fMRI scanning have provided contemporaneous visual representations of individual levels of contra or ipsilateral variations in attention according to handedness (Kim, Ashe, Hendrich, Ellermann, Merkle, Ugurbil, and Georgopoulos, 1993). Habekost and Rostrup (2006) found that patients with brain lesions have impaired visual attention processing in their contralesional hemifield but that ipsilateral function was preserved. Both pieces of research provide supportive evidence for Kahneman’s model of the flexible way in which functioning is organized throughout the brain. His model implies that the brain has several specialist processors throughout and with the recent use of MRI imaging this idea is borne out as the scanner can see active areas of brain functioning. These cognate, specialist processors throughout the brain would account for participant’s ability to multi-task and seemingly divide their attention.

Other physiological evidence of divided attention comes from Von Wright, Anderton and Stenman (1975). They demonstrated a GSR response in participants to words that had been previously paired with an electric shock when they were presented to the unattended ear in a dichotic listening test. As GSR is a function of the involuntary nervous system, this could not be under the participant’s control. This is can be construed as compelling evidence for attentional capacity with more processing power than thought, as the participants demonstrated an observable, involuntary (and possibly unconscious) response to the stimulus in the unattended ear. However, the research still assumed that participants obediently only attended at all times to the information sent to whichever ear the researcher told them to attend to.

Upon consideration, a much simpler explanation of recall from the unattended ear could be that it is as a result of basic physiology. Cochlear neurons would have been stimulated by sound waves and sent action potentials to the brain irrespective of the allocation of attention. This may account for some of the recall from the unattended ear in dichotic listening studies.

Van der Heijden and Bem (1997) argue that the study and conceptualisation of attention has been flawed by a “virtus dormitiva” (1997, p 1). They suggest that the explanation has overemphasised only one aspect of an observed phenomena. In the case of attention, early research indicated that people appear to be limited in what they can attend to and that this had led to a model based on filtration and limitation. Methodologically, some of the experimental methods used could have just been too effortful and impossible to do as they compete for the same cognitive resource (Allport, Antonis and Reynolds, 1972). Allport et al found that participants struggled to learn a list of words when they were spoken to them while trying to listen to a message in the other ear in shadowing tasks. However, if the task does not compete for the same resource then attention can be divided, so clearly the selective attention models do not adequately explain the process fully. Navon and Gopher (1979) argue that some tasks are simply not possible to perform based on the limits of human performance. If dichotic listening is the type of task Navon and Gopher refer to, then the results would have been skewed to demonstrate that attention was limited. Minor changes in replications could produce very different results. For example, Spelke, Hirst and Neisser (1976) demonstrated that very effortful multi-tasking could occur successfully if participants are allowed to practise. Anyone who owns a Nintendo DSTM and plays Dr Kawashima’s Brain TrainingTM will appreciate the practical application of this theory. Clearly, attentional capacity is more malleable than previously thought.

Young and Stanton (2002) concur with Kahneman’s model and support a malleable attentional resource theory. This stipulates that attentional capacity changes in response to the requirements of the task. In driving simulator studies they found that mental workload decreased as some tasks became automatic. Interestingly, they found that the most important factor in attentional capacity is the workload. Their participants were more efficient at completing tasks in the driving condition of their experiment than in the non-driving condition suggesting that familiarity and practise actually increase attentional capacity by automating some functions to make the process more efficient.

People expect to have cars with satellite GPS systems, cup holders, digital music docking stations and other gadgets that all increase demands on attentional capacity. Borrowing from Kahneman’s notion that capacity is not fixed, Young and Stanton’s research goes further to suggest that the capacity is malleable enough to cope with several tasks as a result of practise and automation. However, in January 2008 the Criminal Justice System Sentencing Guidelines Council make the following recommendations regarding those who cause death by driving. They propose that cases involving “momentary inattention” (2008, p 17) should result in sentencing that would leave someone with a criminal record. In their opinion, the use of a mobile phone handset whilst driving constitutes a “gross avoidable distraction” (2008, p 8). Clearly, the research must be careful in the assertion that attentional capacity is malleable without precise reference to occasions where task demands exceed capacity, as they evidently do with potentially fatal consequences.

The implications from Kahneman’s model are that attentional capacity is not fixed. However, it cannot be said the attentional capacity is unlimited either. While experimental research can be flawed and lacking ecological validity, it provides replicable studies that have produced various approximations of models of attention, none of which are completely perfect or without flaws. More research is required to answer questions about which tasks compete for the same attentional resource and overloading capacity. Also, can these results truly be generalized due to the debates about individual differences? Under what circumstances can attentional capacity be increased by practise? Similarly, what circumstances cause it to fail?

A final consideration is that in order to move forward towards an adequate model of attention, van der Heijden and Bem’s article also warns about the “methodology of bad focus” (1997, p1). Models should not aim to remove the inconsistencies of previous models (such as limited attentional capacities or filters) only to refocus the paradigm towards a concept of attentional limitlessness.

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