You’re dumber when your smartphone is within reach

Your smartphone might be making you dumb, a study from the McCombs School of Business at The University of Texas at Austin found. It doesn’t have to ring, buzz, or vibrate either — just having your device nearby is enough to reduce your cognitive capacity.


And we would’ve gotten away with it if not for you meddling scientists!
Image credits Alexandr Borecký.

A team of researchers from McCombs, led by Assistant Professor Adrian Ward recruited almost 800 participants to measure if and to what degree the presence of a smartphone nearby can influence a person’s ability to solve tasks — even when the devices aren’t in use.

The participants were required to take a series of tests on a computer, designed to require full concentration on the part of the testee. The final score would reflect the participants’ available cognitive capacity, a measure of how much information a brain can store and work with at one time. Before taking the test, however, they were randomly asked to place their phones either face down on the desk with the computer, store it in a bag or pocket, or just leave it in another room. All groups were asked to turn their phone to silent so any observed effects would come down to the presence of the phone alone, not random notifications.

Who’s smart now?


Overall, the team found that testees who left their phones in another room “significantly outperformed” those who had placed the phones on the desk, and these in turn slightly outperformed the participants who had their phone in a pocket or bag. The results suggest that the mere presence of the devices is enough to drain somebody’s mental resources and impair their cognitive capacity, even though the participants felt that they were completely immersed in the task presented to them.

And that feeling of single-minded concentration could be exactly why the participant’s processing power dipped.

“We see a linear trend that suggests that as the smartphone becomes more noticeable, participants’ available cognitive capacity decreases,” says Ward. “Your conscious mind isn’t thinking about your smartphone, but that process — the process of requiring yourself to not think about something — uses up some of your limited cognitive resources. It’s a brain drain.”

After establishing what the baseline smartphone-effect looks like, the team investigated how someone’s self-reported feelings of smartphone dependence (how strongly he or she believes to need the device to pass a regular day) influence cognitive capacity. For this step of the study, different participants were asked to take the same computer tests as the first group and were randomly assigned to keep their smartphones either face-up on the desk where it would be easily visible, in a pocket or bag, or in another room. Some participants were also asked to turn off their phones.

Those who reported higher levels of smartphone dependency fared worse than the other participants, the team reports, but only when their devices were kept on their person or on the desk. Whether the phones were turned on or off didn’t seem to matter, nor if it was placed on the desk lying face up or face down — all that was needed to reduce a participant’s ability to focus and perform a task was to have a smartphone somewhere visible and within reach.

Unlike other similar research, however, the team says it doesn’t come down to us delegating some cognitive processes over to the devices and losing on brain ‘exercise’ in the meantime — rather, it’s a matter of self-control. It’s a bit scary to think that we’ve become so attached to the things that your brain actually has to give up part of its processing power to keep the urge of picking them up at bay.


“It’s not that participants were distracted because they were getting notifications on their phones,” said Ward. “The mere presence of their smartphone was enough to reduce their cognitive capacity.”

The full paper “Brain Drain: The Mere Presence of One’s Own Smartphone Reduces Available Cognitive Capacity” has been published in the Journal of the Association for Consumer Research.

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