Suggestion is the psychological process by which one person guides the thoughts, feelings, or behaviour of another. Nineteenth century writers on
psychology such as
William James used the words
"suggest" and
"suggestion" in senses close to those 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
Clark Leonard Hull and others extended the meaning of these words in a special and technical sense (Hull, 1933). The original neuro-psychological theory of hypnotic suggestion was based upon the
ideo-motor reflex response of
William B. Carpenter and
James Braid.