They studied how 26 healthy people walked a short distance (8.5 meters) in three scenarios: while walking normally, while reading texts on a cell phone, and while writing a text themselves. Eight cameras were positioned along the walking path to measure the speed and gait of how people walked, as well as the positioning of their heads, torsos and arms.

The paper itself has some amazingly intricate data on the rotation motion of the pelvis and thorax under each scenario. But suffice it to say: We walk much slower when handling a cell phone (even moreso while texting than reading), and we're not very good at sticking to a straight line. Not surprisingly, we tend to keep our heads down, our necks immobile, and our arms locked at our sides. We don't swing our arms, which can be a crucial part of staying balanced while moving.

Overall, we behave in a way that tries to optimize typing rather than walking, that's more geared toward keeping that little screen stable in our field of vision than keeping ourselves stable.

To illustrate this, here you can watch our own Amanda Erickson walk down a hallway in the Atlantic Cities office. On the left, she's walking normally. On the right, she's trying to type the same phrase used in the study: "The quick brown fox jumps over the lazy dog."

We did not have our own three-dimensional movement analysis system, so you'll have to parse the subtle differences with your eyeballs. But, clearly, it takes Amanda much longer to navigate the hallway while texting, she wanders off-course a bit, her arms barely move at all, and she's not taking in much of what's going on around her. She kind of looks like you could easily tip her over.

Now, picture a hundred pedestrians doing this same thing in a crowded, obstacle-filled public park.

Extra thanks in the name of science to Amanda and Paul Rosenfeld.

Top image: blurAZ /Shutterstock.com

This article is from the archive of our partner The Wire.