another person's tone of voice, facial expressions, and dozens of other cues. This results in what experts call "cyber-disinhibition," where the impulsive circuitry of the emotional brain, usually kept in line by the social circuitry, is freed to express itself. This has long been known as "flaming," classically the sending of a rude, angry or abrasive email that says something the sender would never say face-to-face with the receiver. Flaming has been around as long as the Internet, and now shows up in venues like Twitter and Facebook, let alone sexting. This ups our need for what cognitive scientists call cognitive control -- particularly in the teen years, when the just-say-no circuitry of the prefrontal cortex lags behind the do-it-now circuits of the emotional brain. Cognitive control means we can reign in our impulses in view of the possible consequences. Cognitive control can be taught -- it's a byproduct of attention-training in which kids and teens practice keeping their mind on one point of focus, and noticing when their mind wanders off -- and bring their attention back to that one thing. The results, neuroscientists find, is to strengthen brain circuits for concentration and for reigning in impulse and negative emotions.