Hello everyone. I'm new to this site so please excuse any faux pas I may inadvertently commit.

What I want to know is whether or not Mass Hallucinations actually occur, and what psychologists think causes them. By Mass Hallucinations I'm referring to perception of auditory and visual phenomena without a stimulus by more than one person (or a group). i.e. can hallucinations be shared by groups of people? I'm not referring to things like groups of people experiencing the same symptoms, pains, etc.

Thank you,
sethosayher