Our brains have the capacity to carry out a huge variety of different tasks including those that involve arithmetical calculation and spatial orientation. Nevertheless, research shows that there are limitations on the extent to which the brain can handle rapidly switching between tasks, as is often required from the ever-increasing demands that are placed on our lives (1). We know at least that the complexity of the tasks we undertake greatly influences the speed at which the brain can switch from one task to the next. This is precisely what Joshua Rubinstein from the Federal Aviation Administration and his colleagues David Meyer and Jeffrey Evans from the University of Michigan demonstrated in a practical study published in the Journal of Experimental Psychology several years ago (1).
In their task-switching model Rubinstein, Meyer and Evans proposed that switching between tasks requires that the brain go through what they called ‘executive control processes’. Such processes, they concluded, involve two distinct phases. The first phase–’goal shifting’–describes how the goals and objectives of one task are removed from the immediate memory in the brain and replaced by those of an upcoming task. The second phase–’rule activation’–defines how the brain then sets the rules of engagement through which the goals and objectives of the subsequent task are going to be achieved.
Rubinstein and colleagues suggested that together these two phases ensure that the brain is appropriately configured for efficiently transitioning between tasks. Yet their own research also indicated that in many cases our immediate memories are not large enough to hold more than one set of rules at a time and that simultaneous activation of these rules [e.g. speaking on the phone and driving a car, for instance (2)] could potentially lead to errors in judgment and decision making.
Decreased task familiarity can also greatly increase the time taken to switch from one task to another. Even when an individual is familiar with the goals and rules of an upcoming task, switching time is significantly affected by task complexity, with more complex tasks obviously requiring more time to switch. What does this research mean for the way that we live out our lives? As Rubinstein and his colleagues have noted:
Daily life often requires performing multiple tasks either simultaneously or in rapid alternations as when people prepare meals while tending children or drive automobiles while operating cellular telephones.
In fact, more and more, our lives require us to change rapidly between tasks such as driving and answering the phone. For now it is difficult to determine the exact time cost associated with switching between activities. But, that there is a cost is clear. In the words of one reviewer from the American Psychological Association “the mind and brain were not designed for heavy-duty multitasking” (2).
As a Technical Services Scientist working at Promega, my daily schedule is anything but routine. I do everything from helping customers choose the correct tools for their application to troubleshooting experimental data and analyzing results. The tasks that I perform over the course of a given day are legion, so transitioning between them can be time consuming. Findings such as those outlined in the above study can become relevant not only for how I organize my time but also for how I maintain a desired quality of service.
1. Rubinstein, J.S. et al. (2001) Executive Control of Cognitive Processes in Task Switching. Journal of Experimental Psychology 27, 763–7.
2. The American Psychological Association (2006) Multitasking-Switching Costs.