Testing One Thumb, One Eyeball Mobile Use

by Luke Wroblewski November 26, 2012

People use their smartphones anywhere and everywhere they can, which often means distracted situations that require one-handed use and short bits of partial concentration. Effective mobile designs not only account for these one thumb/one eyeball experiences but aim to optimize for them as well.

It's no secret smartphones get around: at home, throughout the day, at work, while watching TV, during commutes, and beyond. 39% of smartphone users even admit to being on their mobiles in the bathroom, which means the other 61% are liars. But whether we admit it or not, mobile experiences do happen everywhere. And that often includes distractions.

Whether you're on a crowded street corner or on the couch watching TV, chances are you're giving your phone just some of your attention. It's also quite likely that attention doesn't last long. The average person looks at their phone 150 times a day. Most of these are brief interactions lasting a few minutes at best.

Designing for this reality of mobile use requires a laser-like focus on speed and simplicity. But how do you know if you're hitting the mark with a design? Timed, one-handed tests are one way to tell. When designing our new app Polar for Apple's iOS, we did just that.

The core tasks in Polar are voting on and creating photos polls. So these are the interactions we timed and tested with one-handed use. Our goal was to allow anyone to vote on 10 polls or to create a new poll in under sixty seconds using only one thumb. As you can see in the video above, we were able to do just that. In fact, we're often closer to the thirty second mark.

A first time user may take more time as there's usually some context they need to absorb but once someone goes through the flow once or twice, we found under sixty seconds to be easily achievable. Interesting side note: the use of voice input to create a poll wasn't much faster than one-thumb typing in our tests (also seen in the video above).

"What we need to do to design is to look at the extremes. The middle will take care of itself." -Dan Formosa

Clearly there's more to testing and optimizing mobile interaction designs than timed, one-handed tests. But personally I consider this form of observation to be a great litmus test. If people can get things done in time sensitive, limited dexterity situations, they'll be even more efficient when we have their full attention and two-hands focused on our designs.