Walter B. Pillsbury gives a full treatment of the subject in his book on Attention, 1908, and a condensed account of the matter in Chapter V of his Essentials of Psychology, 2nd edition, 1920.

Another full treatment is that of Titchener, in his Textbook of Psychology, 1909, pp. 265-302.

On the topic of distraction, see John J. B. Morgan's Overcoming of Distraction and Other Resistances, 1916.

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CHAPTER XII
INTELLIGENCE