Fascinating! Never really thought about this before, thanks for the link.

(Come to think of it, this seems very song-dependent. For instance, I definitely find myself clapping on 2&4 to "Thriller" and "I Heard It Through The Grapevine". But I think I'd still clap 1&3 to some of my favorite classic rock and metal songs. Also, I felt 1&4 pretty strongly in that Harry Connick Jr. clip. Maybe they're just clapping too fast: if they were only doing half the claps, I think 2&4 would feel more natural.)