Our DD was experimenting with tantrums well before her 1st birthday. We'd put her on timeout in response, and my MIL thought we were being cruel to do so to a child at such an early age, who clearly couldn't know any better. Then DD would spend an afternoon with MIL, where she'd learn fussing or tantrums could be productive, so she'd have to come home and experiment again.
By the time the "terrible twos" arrived she'd pretty much finished with that line of experimentation. We could take her anywhere, and she drew tons of positive attention wherever she went.
