Polaja's Assignments - Cognition

Just some essays and such that I have written at university and recieved good marks in... This is one for Cognitive Psychology.

In terms of doing more than one task at a time, why are there limits to human performance?

In contemporary society, multitasking is seen as an essential skill, however it has long been considered nearly impossible to carry out the processing of two tasks simultaneously (Mei-Ching, Ruthruff & Johnston, 2006). A poignant example in the literature regards the interference caused by talking on a mobile phone whilst driving (Karatekin, Couperus & Marcus, 2004; Schumacher et al., 2001; Wickens, 2002). This interference, termed dual-task interference, has been the subject of many studies in attention and the way that the human brain processes task-related information (Tombu & Jolicœur, 2005). Tombu and Jolicœur (2005) describe dual-task interference as occurring when the attempt to carry out two tasks simultaneously results in either one or both of the tasks suffering in performance. In an effort to understand why these limits to human performance exist, this essay proposes to critically examine the progression of central bottleneck, central capacity, and multi-resource theories of attention. In addition, the question of whether people can overcome this limitation and effectively learn to multitask will be assessed.

The central bottleneck theory was the first developed to explain the cognitive interference found in dual-task studies that made use of the dual-task paradigm (Wickens, 2002). Research in the field of attentional limitations of multitasking has generally been conducted under the dual-task paradigm, which requires the participant to respond to two tasks under time pressure and with inadequate preparation time (Band & Van Nes, 2006). The results of these tasks are measured in terms of accuracy and reaction time, which are then compared to single-task trials of the tasks (Chipunza & Mandeya, 2005). This dual-task paradigm has been used to effectively study attention in speech production (Oomen & Postma, 2001), major depression (Thomas, Goudemand & Rousseaux, 1999), implicit and explicit learning (Shanks, Rowland & Ranger, 2005), time perception (Brown, 1998; Brown & Bennett, 2002), and mental disorders and illnesses (Johannes et al., 2001 Moriarty et al., 2003). The central bottleneck theory proposes that there are three stages of processing, which Tombu and Jolicœur (2005) describe as: the initial perceptual stage, the central processing stage, and the final response stage. The core assumption of this theory is that while the initial and final stages can be carried out parallel with any other stages, the central processing stages can only be processed serially (Band & Van Nes, 2006; Tombu & Jolicœur, 2005). This serial processing is thought to create a structural bottleneck, as when task one is making use of the processing resources, the processing of the second task is delayed (Oomen & Postma, 2001; Tombu & Jolicœur, 2005). Evidence supporting this theory is widespread and still found in research today, even though different theories have been developed to explain the limitations in human performance (Anderson, Taatgen & Byrne, 2005; Ruthruff, Johnston, Van Selst, Whitsell & Remington, 2003; Sangals, Wilwer & Sommer, 2007).

Although much support has been found for the central bottleneck theory, there have been some minor criticisms from researchers who have proposed slight changes to the model. In their review of Hazeltine, Teague and Ivry (2002), Anderson et al. (2005) present that their findings could be predicted by the central bottleneck theory if that theory was expanded to include a memory or learning aspect. This would allow the theory to encompass top-down processing as well as current bottom-up processing. If this were then coupled with the brief central bottleneck and variable duration stages that come with practice, it would be an addition that would make it very difficult to ascertain the difference between this adapted theory and an account that did not make use of the central bottleneck (Anderson et al., 2005). Another example of a minor adjustment to the theory is presented by Sigman and Dehaene (2006) who propose that for the central bottleneck model to account for their results, there would have to be two additions, although by no means do they cite their interpretation of the model as the best or final. The first of these consisted of a stage where task-setting would occur, which was designed to account for the lengthening of task one response times when the two tasks were presented at a short interval (Sigman & Dehaene, 2006). The second proposed modification included the addition of a task-disengagement process, which is intended to account for the cognitive changing between response modalities and the time that this takes (Sigman & Dehaene, 2006).

The central capacity sharing model was developed soon after the central bottleneck theory, and shares many of the same components (Wickens, 2002). Tombu and Jolicœur (2005) explain that in this model, the central processing unit is a parallel processor rather than a serial processor, but extremely limited in capacity. The differing aspect of this model as compared to the central bottleneck model is that the interference is not conceptualised as occurring because of the serial processing of multiple tasks, but instead by the tasks requiring the use of more resources than are available (Chipunza & Mandeya, 2005). This model also has the potential to work as a serial processor, depending on the amount of time that elapses between the presentations of the first and second tasks, making it difficult to differentiate from central bottleneck models (Tombu & Jolicœur, 2003). Tombu and Jolicœur (2003) anticipate this criticism and provide evidence of research in which the distinction of the two models is made clear, concluding that the central capacity sharing model can not only account for the predictions of the central bottleneck model, but also slower reaction times for task one as seen in real-world situations. However, in their modifications to the central bottleneck model of processing, Sigman and Dehaene (2006) may have rendered the need for this unnecessary.

A more serious criticism of the central bottleneck theory can be found in the development of the multiple-resource theory, which can be viewed as an extension of the central capacity sharing model (Tombu & Jolicœur, 2003). This theory claims that the central bottleneck theory is a ‘simple’ explanation and cannot account for the variability in task performance as seen across individuals (Chipunza & Mandeya, 2005; Wickens, 2002). To highlight the inadequacy of the central bottleneck, Wickens (2002) provides the example of performing tasks such as whistling, or tapping fingers or feet. These tasks cause little to no interference with the processing of other tasks that may be carried out at the same time, a prediction not supported by the central bottleneck model (Wickens, 2002). Wickens (2002) goes on to explain that this theory of the reasons behind the limitations of human performance is centred on the notion that there are multiple resources available for processing incoming information, and that they are all relatively independent from one another. An illustration of this theory can be found in research that suggests that dual-task visual and verbal coding of information may be possible to achieve simultaneously, as the different modalities require different brain structures for processing (Chipunza & Mandeya, 2005; Hazeltine et al., 2002). Evidence that can be seen to be against this theory of attentional limitations can be seen in the study of Meinhardt and Pekrun (2003), who found that the processing of events that are emotionally arousing can compete with task-related resources. Chipunza and Mandeya (2005) however, are careful to point out that this model does not necessarily predict that either of the two tasks will not interfere with the processing of the other, just that they will both be performed with a greater efficiency than two tasks that require the same modality for processing.

Each of these attentional models attempts to account for the reasons behind dual-task interference and researchers from each of these viewpoints have studied the effects of practice to see whether or not dual-tasking can be achieved though learning. Researchers trying to either prove or disprove the central bottleneck theory have dominated the research on the effects of practice on dual-task interference, and it has been generally shown that practice does reduce the bottleneck effect of increased reaction times for the second of the dual-tasks (Mei-Ching et al., 2006; Ruthruff et al., 2006; Sangals et al., 2007). In an endeavour to bring the focus of research back to practical issues; Heil, Wahl and Herbst (1999) voiced the concern that researchers seemed to be attempting to assign tasks into the central bottleneck model instead of investigating why they do and do not conform. Another aspect that has been highlighted is that it is equally important to take into account the individual’s goals, motivation and the amount of mental effort that they are willing to exert to accomplish these tasks (Karatekin, Couperus & Marcus, 2004). This reiterates the conclusion of Shumacher et al. (2001) that personality traits, inherent abilities, or responding patterns may have an effect on whether dual-task interference remains after practice.

There have been many different theoretical explanations for this practice effect, such as task automatisation, task integration, and stage-shortening (Mei-Ching et al., 2006; Ruthruff, Van Selst, Johnston & Remington, 2006). Task automatisation refers to a task no longer needing to make use of the central processor as it has been linked to a stimulus-response band elsewhere in the brain; this notion has only received modest support from the research (Sangals et al., 2007). Ruthruff et al. (2006) describe task integration as an amalgamation of the two separate tasks into one overarching task that will reduce the competition for resources, a notion that was not supported by their data. By far the most supporting evidence has been found for the stage-shortening explanation of practice effects, which proposes that the central bottleneck is not eliminated by practice but is made shorter through the stages of the tasks not requiring as much time to be processed (Ruthruff et al., 2006). Mei-Ching et al. (2006) believe that it is this shortening of the central bottleneck that has led many researchers to believe inaccurately that the central bottleneck can be eliminated, whereas it merely remains latent, with the underlying structural limitation still there. This notion has been supported in terms of tasks that are presented to different sensory modalities, effectively disregarding the multiple-resource theory of attentional limitations in favour of a central bottleneck view (Sangals et al., 2007).

The study of the limitations to human performance, when it comes do doing more than one task at a time, has focussed mainly on the structural aspects of the brain. Multiple-resource and central bottleneck theorists hold one idea in common, that there are limited resources that the brain can effectively use to process and respond to tasks (Band & Van Nes, 2006; Wickens, 2002). The major difference between these views is that central bottleneck theorists conceptualise this limitation as occurring when two or more tasks have to be processed through a central processor (Tombu & Jolicœur, 2003), while multiple-resource theorists believe that there are multiple resources available to process different tasks (Chipunza & Mandeya, 2005). Research into the effects of practice on dual-task interference has not been able to confirm the supremacy of either viewpoint (Mei-Ching et al., 2006). However, research has shown that practice is effective in reducing the amount of interference caused by performing two tasks at once, an improvement which in the busy world of today is a prerequisite for success.

References:

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