I tend to look at my phone when I am nervous or bored but have you ever caught yourself pulling out your iPhone, or your Droid, or your BlackBerry and looking at the screen, even though it didn't vibrate or ring?

Yeah . . . everyone does it.

According  to CNN and a study in the journal "Personal and Ubiquitous Computing", the average smartphone user checks their phone 34 times a day for NO REASON.  It's just out of habit.

And when you check it, you do it for about 30 seconds.  Most of the checks happen in clusters . . . a few times within 10 minutes.

Loren Frank is a neuroscientist at the University of California, San Francisco.  He says there's a simple reason why we constantly check our phones.

One, our brains like the feeling of getting an email or text or new Facebook message.  When you see that a new message has arrived, you get a quick happy feeling . . . it's like getting a present.

And once our brains get accustomed to that positive feeling, reaching for the phone moves to a part of the brain called the striatum . . . that's the part that controls habits.