"A number of studies have revealed that game playing triggers dopamine release in the brain, a finding that makes sense, given the instrumental role that dopamine plays in how the brain handles both reward and exploration."
Why Technology Is So Addictive, and How You Can Avoid Tech Burnout, article. (Don't miss the video.)
"Like video games, we can develop a dopamine release from many kinds of addictive behavior. Checking email is one in particular. You may not like spending long amounts of time in your inbox, but you probably think about checking it pretty often. When you hear that ding (or vibrate), you know there's something waiting for you."