References
On images: Galton, as above; D. Hume, A Treatise of Human Nature, 1739, bk. i., pt. i., § 1; J. E. Downey, An Experiment on Getting an After-image from a Mental Image, in Psychological Review, viii., 1901, 42; E. B. Titchener, Lectures on the Experimental Psychology of the Thought-processes, 1909, Lect. 1; Text-book of Psychology, 1910, 194 ff.
On feeling: H. Spencer, The Principles of Psychology, i., 1881, ch. ix.; The Data of Ethics, 1887, chs. vi., vii.; J. M. Baldwin, Mental Development in the Child and the Race: Methods and Processes, 1906, ch. xvi., § 3; W. Wundt, Outlines of Psychology, trs. C. H. Judd, 1907, §§ 7, 12; E. B. Titchener, Lectures on the Elementary Psychology of Feeling and Attention, 1908, Lects. 2-4; Text-book of Psychology, 1910, 225 ff. For experimental methods: Titchener, Experimental Psychology, I., i., 1901, ch. vii.; ii., 1901, ch. vii.; C. S. Myers, A Text-book of Experimental Psychology, i., 1911, ch. xxiv.