“… when still a baby, the elephant is tethered by a very thick rope to a stake firmly hammered into the ground.
The elephant tries several times to get free, but it lacks the strength to do so. After some time, the animal gives up trying, believing that it cannot be free.
At this point, the trainer changes the thick rope to a thin one but the elephant makes no attempt to run away. Even when the elephant reaches adulthood, it continues to be tethered by a thin rope, reconciled to its captivity. ”
[source : http://tinyurl.com/84cems (with thanks to the passing on author)]