Okay, imagine this. You have an end-of-day deadline for a project. You’re nowhere near done. You also have a backlog of emails to process. It’s lunch time. You need to eat. What do you do?
If you’re like many people, you multitask. You respond to email on your phone while walking to get food. You bring your lunch back to the office and work on the project. It feels like you made the best use of your available time. Sound about right?
By now you may know the many dangers of such multitasking. (If not, I wrote a short book that covers them.) But there’s another that isn’t often discussed: multitasking makes us worse at managing our time. It does this by further eroding our already bad ability to estimate task duration.
Let me elaborate.
We’re already pretty bad at estimating task duration. We’re too optimistic by far. Daniel Kahneman and Amos Tversky called it the “planning fallacy.” In one study, for example, 30% of students predicted how long it would take them to complete their theses. On average they were off by 64%, estimating 33.9 days versus the actual 55.5.
Multitasking worsens the problem. When we let ourselves to multitask, it feels as if we’ve multiplied time. This in turn leads us to over-schedule ourselves, because multitasking is an out. “I can always finish that presentation while attending that webinar,” we say. So you put both on your to-do list. Then you do both at the same time, and the quality suffers.
With our devices and apps demanding attention, it’s hard to avoid multitasking. But its probable impact on task duration estimation is another reason to try.