Multitasking vs. Task Switching
Which is easier: Texting while driving or stirring two pans over the stove while occasionally chopping some vegetables for a salad?
In the first instance, you are attempting to do two completely separate tasks, texting and driving. Both tasks require intense concentration as they rely on both the prefrontal cortex and fine motor skills. It's no wonder why texting while driving often has deadly consequences: it isn't possible to text and drive, but you can text or drive.
What about the next example? You are still doing more than one thing at once (in fact, you are managing three tasks) but it doesn't seem as stupid, and in fact we probably do this kind of thing fairly often.
Definitions and Differences
It turns out there is a distinction between multitasking and task switching:
Task switching denotes shifting your full attention from one activity to the next, whereas "multitasking" refers to the attempt to do two or more different tasks at one time.
Most research conducted on multitasking has concluded that a majority of the human population cannot give full attention to two or more tasks requiring a modicum of concentration, especially tasks which require sensory information (visual, auditory, etc).
The same research found that the "cost" of task switching is slightly reduced when tasks are similar and repeated, versus switching between a variety of novel activities (1) And yet, substantial slowing of performance was observed in both multitasking and task switching.
“Psychologists tend to liken [task switching] to choreography or air-traffic control, noting that in these operations, as in others, mental overload can result in catastrophe.”
— American Psychological Association (2)
In experiments done for the Cognitive Neuroscience Society, young adults switched between different tasks, such as solving math problems or classifying geometric objects. For all tasks, the participants lost time when they had to switch from one task to another. As tasks got more complex, participants lost more time. As a result, people took significantly longer to switch between more complex tasks. Time costs were also greater when the participants switched to tasks that were relatively unfamiliar. They got up to speed faster when they switched to tasks they knew better. (3)
Although switch costs may be relatively small (sometimes just a few tenths of a second per switch) I believe it add up to large amounts when agents switch repeatedly back and forth between two chats on different topics. Thus, concurrency may seem efficient on the surface but may actually take more time in the end and lead to more errors. (4)
- Monsell, Stephen, and Jon Driver. Control of Cognitive Processes: Attention and Performance XVIII. Chapter 12. Cambridge, MA: MIT, 2000. The MIT Press. Web. 04 Feb. 2016. Full book available here.
- "Multitasking: Switching Costs." American Psychological Association. N.p., 20 Mar. 2006. Web. 28 Jan. 2016.
- Rubinstein, J., Evans, J. & Meyer, D. E. (1994). Task switching in patients with prefrontal cortex damage. Poster presented at the meeting of the Cognitive Neuroscience Society, San Francisco, CA, March, 1994. Abstract published in Journal of Cognitive Neuroscience, 1994, Vol. 6.
- Meyer, D. E. & Kieras, D. E. (1997b). A computational theory of executive cognitive processes and multiple-task performance: Part 2. Accounts of psychological refractory-period phenomena. Psychological Review, 104, 749-791.