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Unicycling Clowns, Train Wrecks, and Pilots Forgetting to Land

Cell phone use causes inattentional blindness during navigation tasks.

A woman falls down an open manhole while talking on her cell phone. A train operator misses the signals and causes an accident while texting. Pilots fail to notice signals from their plane for an hour and a half while playing with their computers. When people become oblivious to the world, they make potentially disastrous mistakes. How can people miss manholes, train signals, and airports? It couldn’t happen to you or me, could it?

For example, if a clown unicycled past while you were walking, you’d notice wouldn’t you? Probably not if you were talking on your cell phone. In a recent project, my students and I looked at just this question. One student wore a clown suit and unicycled near a common walking path. After people passed our clown, we asked if they had seen him. The good news? Most people saw the clown. Over half of people walking alone and people listening to music players saw the clown. More than 70% of people in pairs saw the clown. The bad news? Only 25% of people talking on cell phones reported seeing the clown. We also found that cell phone users walk more slowly, weave more, and make more direction changes than those not on cell phones. Cell phones disrupt even something as simple as walking. (The CBC aired a documentary titled "Are We Digital Dummies" in Nov, 2010 and included a recreation of our unicycling clown experiment. You can see that segment at this link.)

The cell phone users were generally surprised by how oblivious they were. When asked about that unseen clown, they would turn, look, and wonder how they could have missed him. You can imagine a similar surprised (and pained) response by the woman who fell down the manhole. I suspect the pilots were also surprised when they were interrupted by a flight attendant asking when they would land (Oops, did we miss the airport?). Cell phone conversations make people unaware of the world around them.

Failing to notice the unicycling clown (or Minneapolis if a pilot) is a powerful demonstration of inattentional blindness. When people are actively directing attention to one task, such as a cell phone conversation or a computer interaction, they may fail to become aware of things that pass through their visual field, such as the unicycling clown. The eyes look, but we don’t see. Inattentional blindness highlights a nice strength of human perception – the ability to focus attention. Being able to focus attention means you can ignore distractions and concentrate on the task at hand. If you want to measure your attention focusing ability, check out this cool video awareness test (

Focusing your attention is valuable if you are only performing one task. Dividing attention, however, by trying to do two things at once is risky. When people divide their attention, they perform both tasks more poorly. If you are walking, you want to see a unicycling clown because you don’t know if he’s carrying a cream pie. If you are driving a car, you need to be aware of the world around you. Using a cell phone during tasks such as these divides attention and causes inattentional blindness. When people talk on cell phones while using driving simulators, for example, they miss things like stoplights, their freeway exit, and the brake lights of the car in front of them (see my post "Hang up and drive").

If you are flying a plane, you should focus your attention on that task rather than dividing your attention between flying and using a computer. Luckily, the inattentional blindness of the pilots who were using their computers ended safely for the passengers. The pilots were able to return to the airport somewhat late (but without their jobs).

More from Ira Hyman Ph.D.
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More from Ira Hyman Ph.D.
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