The impulse to constantly check a mobile phone for messages is similar to the feeling people get when they're playing slot machines at a casino, according to a psychology professor.

Steve Joordens, who teaches at the University of Toronto's Scarborough campus, says devices like iPhones and BlackBerries are powerful tools because they allow people to instantly connect with their social networks.

Earning a positive social connection, such as receiving a friendly message or getting passed a link to a funny online video, can feel almost like earning money.

"Social reinforcements are often seen as the currency of the [online] realm," Joordens told Metro Morning contributor Jason Osler.  "So that text from that somebody you met two days ago -- maybe it could wait, but at the same time, if you see that text, it can give you a real jolt, like 'Oh, she didn't forget me.'"

These social rewards -- and how randomly they come -- can keep people tethered to their smartphones like gamblers at a slot machine, Joordens said.

"The reason [slot machines] are so addictive is because a person's pumping in the money, they're pulling the arm, [and] they never know when that will pay off. But they know it will. So randomness has this way of promoting addictive behaviour. You keep waiting for that reward."

Ryerson new media student Keegan Shim knows the feeling well. He has a BlackBerry and estimates he sends and responds to at least 50 text messages a day, not including emails. Shim, 21, said he often feels the need to text during classes and will even respond to a text that wakes him up in the middle of the night.

"Nowadays, I feel like a phone is an extension of my body," he told Osler. "For some reason I just can't be without my phone. If I leave my house and I forget my phone at home, you definitely feel like you're missing something."

How often do you check your mobile phone messages? Do you think you're addicted to your phone? Let us know in the comments below.