Why do your pupils get larger when you're on drugs?

Normally, our pupils dilate in response to changing light; as it gets darker, our pupils get larger. But they expand in size for other reasons as well, including when we're sexually aroused and when we're performing complex cognitive tasks. But it's also known that certain medications — including illicit drugs — can… » 12/07/12 10:40am 12/07/12 10:40am