Multitasking (as done by human beings) considered harmful to productivity?

Question

What evidence or studies suggest or confirm the idea that human multitasking, i.e. people attempting to perform several tasks at once, is harmful to productivity? Is there any evidence to the contrary?

Answer 1

Yes. Basically, everytime you are multitasking you are actually context-switching which is generally less productive in the long run. Have a look at: http://www.amazon.com/Myth-Multitasking-Doing-Gets-Nothing/dp/0470372257

Answer 2

Great blog post on this topic by Joel Spolsky:

http://www.joelonsoftware.com/articles/fog0000000022.html

Explains the concept of why multitasking damages productivity in a very clear way.

Answer 3

You will want to read Flow. Basically, in order to achieve the state of optimum productivity, you need some wind up time in the beginning to get into it. Just as an example, let's say you need 20 minutes of windup to get to peak productivity. If you frequently switch between different tasks, that means more of your work time is spent on the "windup" rather than optimal productivity. The book has studies to back this up.

Answer 4

Definitely harmful. Check out http://en.wikipedia.org/wiki/Human_multitasking:

[...] while there is a great deal of evidence showing the negative effects of multitasking on cognitive tasks [25] [26] [27] [28] [29], there is no evidence showing that multitasking has a positive or neutral effect on these tasks.

• Koch, I., Lawo, V., Fels, J., & Vorländer, M. (2011). Switching in the cocktail party: exploring intentional control of auditory selective attention. Journal of Experimental Psychology. Human Perception and Performance, 37(4), 1140–1147.
• Marois, R., & Ivanoff, J. (2005). Capacity limits of information processing in the brain. Trends in Cognitive Sciences, 9(6), 296–305.
• Strayer, D. L., & Drews, F. A. (2004). Profiles in driver distraction: effects of cell phone conversations on younger and older drivers. Human Factors, 46(4), 640–649.
• Tombu, M. N., Asplund, C. L., Dux, P. E., Godwin, D., Martin, J. W., & Marois, R. (2011). A unified attentional bottleneck in the human brain. Proceedings of the National Academy of Sciences of the United States of America, 108(33).
• Wood, N., & Cowan, N. (1995). The cocktail party phenomenon revisited. How frequent are attention shifts to one’s name in an irrelevant auditory channel. Journal of Experimental Psychology: Learning, Memory, and Cognition, 21(1), 255–260.