Cognitive Science and Philosophy of Mind

Multi-Tasking Research

Dreher, J-C. and K.F. Berman (2002) 'Fractionating the Neural Substrate of Cognitive Control Processes', Proceedings of the National Academy of Sciences 99 (22): 14595-600.

This study observes two significant facts about task-switching and links them to underlying cortical activity via fMRI: 1) switching to a recently performed task takes longer than switching to one less recently performed, and 2) re-engaging in a sequence of tasks after an interruption transiently lengthens response time. These are in line with the theory that switching between tasks requires inhibiting one task and engaging with another: inhibition of the original task remains active for some time and must be overcome if that task is to be re-engaged. The study identifies the brain activity underlying both of these behavioural effects.

Just, M.A. et al. (2001) 'Interdependence of Nonoverlapping Cortical Systems in Dual Cognitive Tasks', NeuroImage 14 (2): 417-26.

This fMRI study indicates mutual constraint in the cortical association areas supporting apparently independent high-level tasks involving two different sensory modalities. In particular, "there is an interdependence among various parts of the cortex, determined in part by the cumulative demands that they impose on brain function in the performance of particular cognitive tasks. This perspective challenges the common assumption of neuroscience and neuropsychology that the modularity and interaction of various cortical systems if a function of only their fixed structural properties...and suggests instead that constraints apply within a dynamically configured large-scale netwrok recruited to perform the task or tasks at hand" (p. 426). The effective interference between visual and auditory tasks means that performance on both decreases when the activities are performed together. One implication of this is that both driving ability and conversational skills are impaired when driving and conversing at the same time. Another titillating implication might be that -- contrary to received wisdom -- the visual interactions counsellors experience with clients could actually impair their abilities to grasp what the client is saying. Impairment of language comprehension was more pronounced than visual impairment, with the brain's activation for listening some 53% lower when the subject was attending to a visual task at the same time.

Pashler, H. (1992) 'Attentional Limitations in Doing Two Tasks at the Same Time', Current Directions in Psychological Science 1: 44-8.

This study on the PRP, or psychological refractory period, suggests severe limits on the mental activities which subjects can perform at the same time, indicating that response selection is affected by a fundamental bottleneck that is virtually impervious to practice. See Schumacher et al. (2001) for a counterbalancing view.

Rubinstein, J.S.; D.E. Meyer and J.E. Evans (2001) 'Executive Control of Cognitive Processes in Task Switching', Journal of Experimental Psychology: Human Perception and Performance 27 (4): 763-97.

The upshot of this lengthy article reporting research on subjects' abilities to switch between disparate cognitive tasks is that performance degrades quickly with task complexity and that serial task processing is significantly more efficient due to the time lost in switching. The study supports a model of task switching that incorporates distinct stages for switching itself and for engaging the rules associated with the new task.

Schumacher, E.H. et al. (2001) 'Virtually Perfect Time Sharing in Dual-Task Performance: Uncorking the Central Cognitive Bottleneck', Psychological Science 12 (2): 101-8.

Challenging studies such as Pashler (1992), this article reports three experiments which demonstrate that at least some subjects can achieve, with practice, virtually perfect time sharing in dual-task performance of basic choice reaction tasks. The authors distinguish between 'conservative' and 'daring' task scheduling and indicate that, when required, conservative control may postpone one task while another is already underway, yielding the usual dual-task interference. Rather than a fundamental cognitive bottleneck, they suggest that, "personal preferences for cautious rather than daring task scheduling underlie individual differences in dual-task interference" (p. 102).

Shellenbarger, S. (2003) 'New Studies Show Pitfalls of Doing Too Much at Once', Wall Street Journal 27 February 2003.

This article reviews some of the recent research on multi-tasking -- including some of the articles included here in this section -- and cautions against too much of it. The author quotes David Meyer (a co-author of Rubinstein et al. (2001), for instance) as suggesting that the stress response induced by intense multi-tasking can interfere with short-term memory.