Worker, Interrupted: The Cost of Task Switching

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Gloria Mark

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We found there is significantly more stress. We did a laboratory experiment where people did a typical office task: they had to answer a set of e-mail. In one condition, they were not interrupted. In another condition, we interrupted them with phone calls and IM. We used a NASA workload scale, which measures various dimensions of stress, and we found that people scored significantly higher when interrupted. They had higher levels of stress, frustration, mental effort, feeling of time pressure and mental workload. So that's the cost.

There was no significant difference in number of errors between those who were interrupted and those who were not. But I'll tell you something very interesting that we found -- when people were not interrupted they worked slower. Here's how we interpret that -- when people know they can expect interruption they get into a mode of working faster to compensate. You know you're going to be continually interrupted so you compensate by working faster, but the cost of that is stress.

How do you explain the stress?

It's a feeling of just not being able to keep up. There was very high powered lawyer on the east coast who told me that every Sunday morning he wakes up before the rest of his family, clears off the dining room table, lays out all his casework and spends the entire Sunday just catching up on what he wasn't able to complete during the week. That's another dimension -- the inability to just get away from work and take a break. It's what I call invisible work: the work that your colleagues and managers don't see, the extra work you have to get done just to keep up with the demands of the workplace.

Are we becoming more superficial thinkers?

I argue that when people are switching contexts every 10 and half minutes they can't possibly be thinking deeply. There's no way people can achieve flow. When I write a research article, it takes me a couple of hours before I can even begin to think creatively. If I was switching every 10 and half minutes, there's just no way I'd be able to think deeply about what I'm doing. This is really bad for innovation. When you're on the treadmill like this, it's just not possible to achieve flow.

But many people tout the information revolution as a great spawning ground for creativity -- we're coming into contact with new ideas, forging new connections, tapping into new networks. Do you buy any of that?

You have to put that in perspective. Let me give you an example. Eleven years ago I was a researcher at the Boeing company I studied a virtual world that was being deployed so people in the distributed company of Boeing would be able to meet others share expertise. It was basically like Second Life. We deployed this and we could not get anyone to use it. They went there out of curiosity and then they left and never came back. Eleven years later with Second Life, with all due respect, we're seeing exactly the same thing. People come, they're curious and then they don't come back.

Certainly, technology is giving us access to a lot more different people, but how many of these end up being quality relationships? That's the question we really have to ask.

You're the expert -- how do you protect productive time?

I stay home. I do have to go into the university on some days but I try to schedule appointments so that I can stay home as much as I can, because that's the only way I'm not going to be interrupted.

What advice do you give to people who feel like they can't keep up?

Limit your web usage. Be disciplined. I am the most productive if I limit web usage to twice per day, once in the morning and once at night. To be more realistic, it's usually like four times a day that I check e-mail. If I do that, I can be really productive.

Be honest: have you been checking e-mail during this conversation?

I have to confess, I did once or twice.