Well, i know one of the earliest octo experiments was for two octos to be put in adjacent tanks. Scientists put a red ball and a white ball in the tank of one of the octos, called the demonstrator.The scientists would then reward the demonstrator octo for attacking the white ball with food. They would "punish" the octo with an electric shock if it attacked the red ball. They then allowed the second octo, called the observer to watch the demonstrator. Turns out that without any previous conditioning the observer attacked the white ball almost every time. I don't know if that's a "trick" (which is really not the correct term, but who cares), but I thought It was pretty interesting.