Why is multitasking so hard? The cost of shifting attention
Doing two things at once really means switching between them fast. Task-switching research explains what each switch costs.
You answer messages, listen to a meeting and edit a document at the same time. It feels like everything is getting done, yet afterward little of it sticks. Cognitive science explains why fairly clearly.
A checkpoint that lets one thing through
When people do two simple tasks almost simultaneously, their response to the second is noticeably delayed. Reviewing such studies in 1994, Harold Pashler argued that the stage of choosing a response is a bottleneck that handles one task at a time. Even when two things seem to happen at once, the critical step is waiting its turn.
A cost every time you switch
In 1995 Robert Rogers and Stephen Monsell had participants alternate between two tasks. Responses were slower and errors more frequent when the task changed than when it repeated. Telling people what was coming and giving them time to prepare did not make this switch cost disappear entirely. Swapping the rules in your head takes time, and holding those rules involves working memory and the prefrontal cortex.
Hands-free doesn’t help
In a 2001 driving-simulator study by David Strayer and William Johnston, talking on a cell phone made drivers miss signals or react late more often. Results were similar with hands-free phones. The problem was attention, not hands.
Does practice make perfect?
In 2009 a Stanford team compared people who habitually use many media at once with those who do not. Surprisingly, heavy media multitaskers were slower on a task-switching test and more easily distracted by irrelevant information. Multitasking more often did not make people better at switching.
In short
Rather than handling several things at once, the brain switches between them quickly and loses a little time and accuracy with each switch. Turning off notifications during important work is less a matter of willpower than a choice that respects how the brain is built.
Sources
- Dual-task interference in simple tasks: data and theory. Pashler H. Psychological Bulletin 116, 220–244 (1994)
- Costs of a predictable switch between simple cognitive tasks. Rogers RD, Monsell S. Journal of Experimental Psychology General 124, 207–231 (1995)
- Driven to distraction: dual-task studies of simulated driving and conversing on a cellular telephone. Strayer DL, Johnston WA. Psychological Science 12, 462–466 (2001)
- Cognitive control in media multitaskers. Ophir E, Nass C, Wagner AD. PNAS 106, 15583–15587 (2009)
