[Texting] discourages thoughtful discussion or any level of detail. And the addictive problems are compounded by texting's hyperimmediacy. E-mails take some time to work their way through the Internet, through switches and routers and servers, and they require that you take the step of explicitly opening them. Text messages magically appear on the screen of your phone and demand immediate attention from you. Add to that the social expectation that an unanswered text feels insulting to the sender, and you've got a recipe for addiction: You receive a text, and that activates your novelty centers. You respond and feel rewarded for having completed a task (even though that task was entirely unknown to you fifteen seconds earlier). Each of those delivers a shot of dopamine as your limbic system cries out "More! More! Give me more!
Daniel J. Levitin, The Organized Mind: Thinking Straight in the Age of Information Overload
addiction, text-messaging, texting