I vaguely remember reading about a study where a person walked out into a cornfield that was frequented by crows every morning. Every day he'd carry a loaded ri

I vaguely remember reading about a study where a person walked out into a cornfield that was frequented by crows every morning. Every day he'd carry a loaded rifle, but on some mornings the rifle would be internally disabled. Although there was no way to tell visually if the rifle was capable of firing or not, the crows would immediately disperse on days when it was, and would ignore the man on days when it wasn't. The assumption was that they based their reaction on unconscious body language, which seems rational enough.