Suggestion is the name given to the psychological process by which one person may guie the thoughts, feelings or behaviour of another. For nineteenth century writers on psychology such as William James the words "suggest" and "suggestion" were used in senses very close to those which they have in common speech; one idea was said to suggest another when it brought that other idea to mind. Early scientific studies of hypnosis by scientists such as Clark Leonard Hull led to the extension of the meaning of these words in a special and technical sense (Hull, 1933).