Throughout history, most of what was to be learnt, by most people, was learnt in everyday life. Children watched and imitated adults, negotiating what was acceptable or desirable. Younger copied older siblings, peer groups mutually tried out actions and behaviour. Some children have been noticeably quicker than average in reproducing adult skills, and some noticeably slower. A few have not acquired the normal skills and behaviour, long past the expected time, regardless of rewards and sanctions.