William James devoted much thought to the problem of the mechanism of learning, habit, association, etc., and his conclusions are set forth in several passages in his Principles of Psychology, 1890, Vol. I, pp. 104-112, 554-594, and Vol. II, pp. 578-592.

Another serious consideration of the matter is given by William McDougall in his Physiological Psychology, 1905, Chapters VII and VIII.

See also Thorndike's Educational Psychology, Briefer Course, 1914, Chapter VI.

On the whole subject of association, see Howard C. Warren, A History of the Association Psychology, 1921.

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CHAPTER XVII
PERCEPTION