cognitive capacity is reduced whenever our phones
are within reach, whether it’s turned on or off.
Although these devices have immense potential to
improve welfare, their persistent presence may come
at a cognitive cost.
Results from two experiments
indicate that even when people are successful at
maintaining sustained attention — as when avoiding
the temptation to check their phones — the mere
presence of these devices reduces available
Moreover, these cognitive costs
are highest for those highest in smartphone
McCombs Assistant Professor
Adrian Ward and co-authors conducted experiments
with nearly 800 smartphone users in an attempt to
measure, for the first time, how well people can
complete tasks discussing the practical implications
of this smartphone-induced brain drain for consumer
decision-making and consumer welfare.
In one experiment, the
researchers asked study participants to sit at a
computer and take a series of tests that required
full concentration in order to score well.
The tests were geared to measure
participants’ available cognitive capacity — that
is, the brain’s ability to hold and process data at
any given time.
Before beginning, participants
were randomly instructed to place their smartphones
either on the desk face down, in their pocket or
personal bag, or in another room.
All participants were instructed
to turn their phones to silent.
The researchers found that
participants with their phones in another room
significantly outperformed those with their phones
on the desk, and they also slightly outperformed
those participants who had kept their phones in a
pocket or bag.
The findings suggest that the
mere presence of one’s smartphone reduces available
cognitive capacity and impairs cognitive
functioning, even though people feel they’re giving
their full attention and focus to the task at hand.
“We see a linear trend that
suggests that as the smartphone becomes more
noticeable, participants’ available cognitive
capacity decreases,” Ward said.
“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
It’s a brain drain.”
Imagine if phones knew when to
let us focus.
In another experiment,
researchers looked at how a person’s self-reported
smartphone dependence — or how strongly a person
feels he or she needs to have a smartphone in order
to get through a typical day — affected cognitive
Participants performed the same
series of computer-based tests as the first group
and were randomly assigned to keep their smartphones
either in sight on the desk face up, in a pocket or
bag, or in another room.
In this experiment, some
participants were also instructed to turn off their
The researchers found that
participants who were the most dependent on their
smartphones performed worse compared with their
less-dependent peers, but only when they kept their
smartphones on the desk or in their pocket or bag.
Ward and his colleagues also
found that it didn’t matter whether a person’s
smartphone was turned on or off, or whether it was
lying face up or face down on a desk.
Having a smartphone within sight
or within easy reach reduces a person’s ability to
focus and perform tasks because part of their brain
is actively working to not pick up or use the phone.
“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
For more information
Brain Drain: The Mere Presence of One’s Own
Smartphone Reduces Available Cognitive Capacity
The University of Texas at Austin