You know that thing where someone you don't know is waving at you and you wave back, then you realize they were waving at the person standing directly behind you? You smile, perhaps look a bit confused, but above all else you're humiliated by the encounter. Why does that happen? It's a mistake that everyone makes all the time, and for some reason it's still an awkward, shameful experience of outsize proportions. We need to work on not feeling so bad when we accidentally wave back.