According
to this article in the NYT, the art of texting reduces one's IQ:
“The act of texting automatically removes 10 I.Q. points,” said Paul Saffo, a technology trend forecaster in Silicon Valley. “The truth of the matter is there are hobbies that are incompatible. You don’t want to do mushroom-hunting and bird-watching at the same time, and it is the same with texting and other activities. We have all seen people walk into parking meters or walk into traffic and seem startled by oncoming cars.”
Judging by some of the conversations one hears on mobile phones, especially on the move in trains etc by loud peoples, actually talking reduces IQ by a lot more