The suggestion also arises as to whether those performances which do not cohere closely with performances in general are such as involve the sensori-motor apparatus to a special degree, as distinguished from the central nervous system. Those functions which depend relatively little upon equipment of eye, ear, or hand, but essentially upon the sensitivity and integrity of the cortical neurones, might be expected to cohere closely, constituting what we should properly call intelligence. Where performance depends largely on sense organs and muscles, the correlation with functions largely independent of sensori-motor apparatus might be expected to be only as great as the tendency to general organic quality would bring about. Certainly drawing, music, and mechanical ability, for example, involve eye, ear, and muscle to a much greater extent than does the detection of absurdities in life situations, or the learning of symbolic significances. The mechanical technique of reading clearly involves the sensori-motor apparatus to a much greater extent than does the comprehension of what is read. It would be valuable to determine to what extent a hierarchy of correlations would be consistently maintained in the use of tests, selected for graduated degrees of involvement of equipment accessory to the central nervous system.[8] REFERENCES BAERWALD, R.—_Theorie der Begabung_; Reisland, Leipzig, 1896. BINET, A., and SIMON, TH.—“Théorie nouvelle de la démence”; _L’année psychologique_, 1909. BROWN, WM.—“Some Experimental Results in the Correlation of Mental Abilities”; _British Journal of Psychology_, 1909–10. BURT, C.—“Experimental Tests of General Intelligence”; _British Journal of Psychology_, 1909–10. BURT, C.—_Mental and Scholastic Tests_; London County Council, 1921. HART, B., and SPEARMAN, C.—“General Ability, Its Existence and Nature”; _British Journal of Psychology_, 1912. HART, B., and SPEARMAN, C.—“Mental Tests of Dementia”; _Journal of Abnormal Psychology_, 1915. HOLLINGWORTH, H. L.—_Judging Human Character_; D. Appleton and Co., New York, 1922. MCCALL, W. A.—_Correlation of Some Psychological and Educational Measurements_; Teachers College, Columbia University, 1916. MCCALL, W. A.—_How to Measure in Education_; The Macmillan Company, New York, 1922. MOORE, T. V.—“The Correlation between Memory and Perception in the Presence of Diffuse Cortical Degeneration”; _Psychological Monographs_, 1919. RÉVÉSZ, G.—“Ueber das frühzeitige Auftreten der Begabung”; _Zeitschrift für angewandte Psychologie_, 1919. RUGG, H. O.—_Statistical Methods Applied to Education_; Houghton Mifflin Co., Boston, 1917. SIMPSON, B. R.—_Correlations of Mental Abilities_; Columbia University, 1912. SPEARMAN, C.—“The Proof and Measurement of Association between Two Things”; _American Journal of Psychology_, 1904.