15. Tactile adaptation. Support two fingers on the edge of a table, and lay on them a match or some other light object. Let this stimulus remain there, motionless, and notice whether the tactile sensation remains steady or dies out. What is the effect of making slight movements of the fingers, and so causing the stimulus to affect fresh parts of the skin? 16. Temperature sense adaptation. Have three bowls of water, one quite warm, one cold, one medium. After holding one hand in the warm water and the other in the cold, transfer both simultaneously to the medium water and compare the temperature sensations got by each hand from this water. State the result in terms of adaptation. 17. Overtones. These can be quite easily heard in the sound of a large bell. What use does the sense of hearing make of overtones? REFERENCES For a somewhat fuller discussion of the topic of sensation, see Warren's _Human Psychology_, 1919, pp. 151-214; and for a much fuller discussion, see Titchener's _Textbook of Psychology_, 1909, pp. 46-224. {243} For a really thorough consideration of the facts and theories of color vision, see J. Herbert Parsons, _An Introduction to the Study of Colour Vision_, 1915. For a more complete statement of the Ladd-Franklin theory, see the article on "Vision", in Baldwin's _Dictionary of Philosophy and Psychology_, 1902. For a recent study that has revolutionized the psychology of the sense of smell, see _Der Geruch_, by Hans Henning, 1916, or a review of the same by Professor Gamble in the _American Journal of Psychology_, 1921, Vol. 32, pp. 290-296. For an extensive discussion of the "Psychology of Sound", sec the book with this title by Henry J. Watt, 1917. For a full account of taste, see Hollingworth and Poffenberger's _Sense of Taste_, 1917. {244} CHAPTER XI ATTENTION HOW WE ATTEND, TO WHAT, AND WITH WHAT RESULTS