Auto-Nod

When you're talking with someone, and you're distracted, bored, disinterested, etc. you put yourself on "Auto Nod" by periodically nodding at them (with the occassional "uh huh" or "really?") to give the impression you're paying attention, when in fact you're plotting their demise, your escape, wondering what's on TV tonight, pondering the difference between "affect" and "effect" etc.