It's been 10 years since the first iPhone was sold in stores — and the millions of people who now own one likely won't dispute that having the internet, social media and countless apps at their fingertips can sometimes be a distraction.

But new research shows that even when people aren't using them, simply having smartphones nearby compromises their ability to think and perform other tasks.

"The present research identifies a potentially costly side effect of the integration of smartphones into daily life: smartphone-induced 'brain drain,'" says the study, published in the Journal of the Association for Consumer Research.

Researchers at the McCombs School of Business at the University of Texas at Austin measured the cognitive performance of 520 undergraduate study participants through two tasks: the completion of math problems while remembering a sequence of letters, and the completion of a pattern sequence.

Adrian Ward

Even when people are 'avoiding the temptation to send a text message or check Twitter or watch a cat video,' the mere presence of their smartphones reduces the cognitive capacity they have to perform tasks, says psychologist Adrian Ward, the study's lead author. (McCombs School of Business/University of Texas at Austin)

Some of the students had been told to leave their belongings, including their smartphones, in the lobby outside the testing room. Others were allowed to keep their phones with them in their bags or their pockets. A final group kept their smartphones and were told to place them face down on the desk.

Under all three circumstances, the participants were told to turn both the ringer and vibrate functions off.

The study found that the participants who had their smartphones on their desks performed significantly worse than those who left their phones outside the room, suggesting decreased cognitive capacity. And those who had their phones in their bags or pockets performed somewhere in the middle.

The results suggest "our smartphones can reduce our ability to do other tasks just when they're in our environment, not just when we're using them," Adrian Ward, a psychologist and the study's lead author, told CBC News.

That's because people are so used to having constant access to text messages, emails, social media, apps, information and entertainment that the very act of trying to ignore the presence of the device providing those things takes brain power in and of itself, he says.

"Even when you're being successful at, you know, avoiding the temptation to send a text message, or check Twitter, or watch a cat video — whatever it happens to be — just having [your smartphone] in the environment, having that opportunity for distraction, reduces the cognitive capacity you have for the task at hand," Ward said.

Nathaniel Barr, a cognitive psychologist and professor of creative thinking at Sheridan College in Oakville, Ont., has also done research on the relationship between smartphones and how people think. He has no affiliation with the University of Texas at Austin study.

Benefits vs. drawbacks

While he said he agrees with the study's findings, Barr emphasized the importance of noting the cognitive benefits that smartphones provide, along with the potential costs — especially when looking at their use in workplaces or schools.

"I agree with their conclusions that, in a lot of instances, it probably makes sense to set these devices aside," Barr said. "But I also think that that should be qualified by the type of work you're trying to do: whether you need your sole focus or whether you need to seek other sorts of information outside of your own head.

Nathaniel Barr

Nathaniel Barr, a psychologist and professor at Sheridan College in Oakville, Ont., says he agrees with the study's conclusions but notes that the cognitive impact of smartphones — both positive and negative — need to be weighed in individual workplaces and educational settings. (Nathaniel Barr)

"In a purely computational-power-of-your-brain-type setting, yeah, it's probably best to have your phone away," he said. "If it's something where you're continually having to outsource answers or find actual content … it probably makes sense to have these devices handy."

Ward acknowledges the study focused on specific cognitive tasks that require high levels of concentration, and noted more research is needed to determine how the presence of smartphones affects how people think in different types of work environments, classrooms and social situations.

The question, he said, is how to use smartphones in the most constructive way possible from a brain power perspective. 

"I don't think that the answer there is throwing your smartphone to the bottom of the ocean," Ward said.

"It's important to know how they're affecting our cognition and when, so that we can address that and sort of draw some boxes potentially around the technology in our lives and take back the reins."