On imagery, synesthesia, etc., see Gallon's Inquiries into Human Faculty and Its Development, 1883, pp. 57-112; and for more recent studies of imagery see G. H. Betts on The Distribution and Function of Mental Imagery, 1909, and Mabel R. Fernald on The Diagnosis of Mental Imagery, 1912.

On the diagnostic use of the association test, an extensive work is that of C. G. Jung, Studies in Word-Association, translated by Eder, 1919.

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CHAPTER XVI
THE LAWS OF ASSOCIATION