When Keller and Marian Breland, two psychologists who became animal trainers, decided that it would be cute to have a pig drop a big wooden coin into a box, they found that ________.
◦ food was not an effective reinforcer for the pig and so learning didn't occur
◦ when given edible roots as reinforcers, the pig learned the task in less than ten trials
◦ the pig displayed instinctive drift by dropping the coin and pushing it around with its nose
◦ the pig showed intrinsic interest in the task and so reinforcement was unnecessary