Green light to talk to me FlowLight Team

Can’t you see I’m busy? A desk-mounted traffic light system automatically measures how hard a person is working to tell would-be interrupters when to stay well away.

The FlowLight system tracks keyboard strokes as well as mouse clicks and movement to detect whether a worker is in the zone or can be disturbed. If a person’s combined keyboard and mouse activity is within the top 9 per cent of their average activity range, then an LED attached to their desk glows red, warning colleagues not to bother them.

If the worker drops below the 9 per cent activity threshold, their LED turns green, indicating they are more open to interruptions at that point.


David Shepherd at ABB, an industrial engineering company, devised the system to keep the firm’s software engineers on track during the workday. Interruptions can be particularly annoying for so-called knowledge workers who have to think creatively and handle large amounts of information at the same time, he says. “When you interrupt them, it’s a disaster.”

So Shepherd enlisted the help of Thomas Fritz and his team at the University of Zurich in Switzerland to build a system that could cut down the number of interruptions software engineers experience. Fritz tested the system with 449 employees across ABB offices in 12 countries, finding that people typically experienced 46 per cent fewer interruptions when they were using the FlowLight system.

The results of the study are being presented at the May ACM Conference on Human Factors in Computing Systems in Colorado.

Guiding light

FlowLight isn’t intended to make people feel guilty about slacking when their light switches from red to green, says Fritz. To reduce the risk of this inadvertently happening, he designed the system so the light is only red for 13 per cent of each day, no matter how hard the person is working. And the system doesn’t discriminate between clicking for work and scrolling through Facebook or doing online shopping, for example.

Jelmer Borst at the University of Groningen in the Netherlands is a fan of FlowLight, but he thinks there might be a better way of judging how hard someone is working.

Tracking keystrokes and mouse clicks only measures time spent interacting with a computer, not time spent thinking, he says. He suggests instead using pupil dilation to measure how hard someone is working. The higher their cognitive load, the more dilated their pupils, he says.

Pupil-tracking cameras are probably too costly to use, says Shepherd, but his team is experimenting with other forms of biometrics. Future versions of FlowLight could use heart rate trackers to measure how hard someone is working, he says.

Shepherd has a FlowLight bulb on the outside of his office, which has been deterring untimely visitors for two-and-a-half years, he says. “You’ll hear footsteps and then you’ll hear them carry on past my door when they see the light.”

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