So one theory is--is a signal of mock aggression and collective aggression.

因此，一种理论是——这是假装侵略和集体侵略的信号。

And collective aggression--a lot of mob assaults, executions, lynchings, rapes are accompanied with the sound of laughter.

还有集体侵略——许多暴民袭击、处决、私刑、强奸都伴随着笑声。