Could there be a sonic weapon which broadcasts the sound of a yawn over the battlefield to cause a momentary wve of yawns across the enemy soldiers?

Perhaps there are other hardwired sympathetic responses that can be taken advantage of in this way. I suspect that, the same way that pickup artists have their little book of tricks for manipulating women, there might be a collection of psychological tricks that can be used on enemy soldiers to hack their biology.

But the most entertaining to me, is the yawn cannon. Just writing about it makes me want to yawn. I've yawned three times now already.