In times gone by, mahouts would train their elephants to stand and wait patiently by taking them — as babies — through a “conditioning” process. First, they would lead the babies out to where the adult elephants were working and tie a large chain around their necks and to a large tree. Playful, intelligent and curious the babies would try all sorts of ways to get free of the chain but eventually they learned that with a chain around their necks they could not escape. The mahouts would then exchange the chain for a heavy rope, and the elephants were bright enough to notice the difference and their escape attempts would begin again, albeit will less vigour. After a while, they would decide that with the rope around their necks they couldn’t escape. Once again, the mahouts would change the rope for a thin twine and this time the baby elephants would only make a token effort to escape — after all, they were learning that with something around their necks and around a tree — they were stuck. When they finally stopped their attempts to wander off, the mahouts would replace the twine with a simple, short lead attached to a small wooden handle. They would use this to lead the elephant to where they wanted them to stand, and just let go of the lead. They no longer tied the lead to anything — the elephants were intelligent enough (?!) to know that if there was anything around their necks they were stuck.
Here is an experiment you can do with your children (if you are reckless) or just take my word for it. Fill a small fish aquarium with a family of fleas, keping a tight glass lid on the top. Watch them jump so high they bump into the glass ceiling. Over time, they learn to jump less high and avoid banging themselves against the glass lid. A while later, you can remove the lid and the fleas will not jump out. They have learned the limits of their world.
Never happens to humans of course!!