When you hold a smartphone in your hands, you have the world at your fingertips; but this doesn’t mean that the little gadget is empowering your brain. Actually, it might be having the opposite effect. A recent study conducted by researchers at the University of Texas at Austin suggests that just having your smartphone in viewing distance lowers your cognitive capacity and overall brain power. 
The team at UT Austin gave people a test that gauged attention control and cognitive processes. They found that the ability to maintain and process data improved dramatically when the person’s smartphone was in another room during the test. Participants who kept their phones locked away in a pocket or bag also performed better on the tests than those who were within glancing distance of their smartphone.
Even if a smartphone was turned off or was put face-down, it still appeared to zap the owner’s cognitive resources. 
Adrian Ward, one of the researchers behind the recent study, says:
“It’s not that the participants were distracted because they were getting notifications on their phones. The mere presence of their smartphone was enough to reduce their cognitive capacity.” 
Let’s pause for a moment. Be right back.
OK, thanks for waiting. I wanted to put my phone in another room.
In light of the study’s findings, it kind of makes sense that a group in Colorado called Parents Against Underage Smartphones, or PAUS, wants to ban smartphone sales to children under 13. The process wouldn’t be terribly different from that used to limit sales of tobacco and alcohol to adults. Under PAUS’s proposed ballot initiative, retailers would be required to submit verification reports to the state government on the intended user of the smartphone. Retailers who repeatedly fail to comply could be fined.
Now such a ban might never happen; many people think that the proposal goes too far, and there are legitimate reasons to be against such a rule. (Would retailers honestly report selling a phone to children under 13, anyway?) But the UT Austin study really makes you wonder… what are these smartphones doing to kids’ developing brains?
After all, a 2016 study found that just thinking about mobile devices disrupts kids’ sleep.
“We see a linear trend that suggests that as the smartphone becomes more noticeable, participants’ available cognitive capacity decreases. 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.” 
Kind of like willing yourself not to think about sex. Oops, you just failed. That’s a split second of your life you could have dedicated to just thinking about sex.
If this sounds like phony baloney, consider this: Those who were the most dependent on their phones performed the worst on tests, but none of them felt that the location of their phones had any effect on their concentration level or cognitive abilities.
 Psychology Today
 Science Alert