Papousek began his studies by using milk in the normal way to reward the babies and so teach them to carry out some simple movements, such as turning the head to one side orthe other. Then he noticed that a baby who had had enough to drink would refuse the milk but would still go on making the learned response with clear sign of pleasure . So he began tostudy the children s responses in situations where no milk was provided. He quickly found that children as young as four months would learn to turn their heads to right or left if the movement switched on a display of lights — and indeed that they were capable of learning quite complex turn to bring about this result, for instance, two left or two right, or even tomake as many as three turns to one side.