The monkeys came from three different groups (it was difficult to find one large group) and had been raised in some degree of captivity.

ECONOMIST: Health indicators

When facing a "loss" either way, the monkeys preferred the chance of getting three half of the time--even though the expected payoff in all cases was the same.

FORBES: Magazine Article

But if ten million monkeys sitting at typewriters can reproduce the works of Shakespeare, it stands to reason that three million bored iPhone owners would push enough buttons to find a backdoor this simple.

FORBES: Careful, iPhone Owners: Simple Backdoor Lets Anyone Bypass Password Protection

After three months the level of dopamine in their brains had dramatically increased and were similar to those found in younger monkeys.

BBC: Woman's hand