"Easy Pupil" action

[gintarė]

It was when I was eleven. I can remember one game or a sort of experiement. It was usually done in school in pauses between classes: one pupil sat on the window sill. Three others stood around on three sides. In front of him, on the left and the right. Pupil on the window closed his eyes. Everyone of the three boys clasped his hands like that:

They pointed they hand-guns at the kid's head. Then one of the participants gave a signal with his head. And they picked up the window pupil high just on their fingers. Actually they tossed him up! He became like a down. But if somebody laughed or suppressed laughter the experiement went bad. The window-pupil got unexpectedly heavy
Could somebody explaine what it was? Thanks!

[Horny Goat]

This is such a common experiment that kids do as soon as they learn it but I don't think anyone can explain it. I wonder if Randi & co. can explain it.

[Nahemah]

It's scientifically explainable:

http://www.abc.net.au/science/articles/ ... 257305.htm

Timing is everything. Hence the chanting etc.