At two months, Nim was scaling the walls. 'His physical prowess just escalated,' says Stephanie. 'If he wanted to defy you, he had the upper hand in every way. We tried to spank him - just stop him.' In despair, she tried psychological tactics. When he behaved badly, she walked out of the room. The threat of abandonment made Nim panic. He stopped whatever he was doing and ran after Stephanie for a reassuring hug. He learnt to sign 'sorry', and did so often. Nim became a major attraction for Columbia students, eager to baby-sit the chimp or simply hang out with the LaFarges. At night, joints were passed around the living room as Nim jumped up and down on the water bed. Sometimes Nim would take a puff on the joint and inhale with pleasure. (A few years later, he would ask for a joint in sign language by combining three signs: 'stone'; 'smoke'; 'now'.)