The tests on which Figures 6, 7, and 8 were based included practically all which were reported in the researches used. They were as follows: Norsworthy (_159_), perception of 100-gram weight, cancelling A's (boys), ideas remembered from four simple sentences, memory of related and of unrelated words, part-wholes, genus-species, opposites and reverse of opposites given the next day, “a-t” test. J. Allen Gilbert (_108_), taps in 5 seconds, fatigue in tapping, visual reaction time, color-discrimination reaction time, reproduction of 2-second interval. Smedley (_51_, No. 3), strength of right-hand grip (boys), taps in 30 seconds (boys), ergograph; visual, auditory, audio-visual, and audio-visual-articulatory memory for digits. W. H. Pyle, Standards of Mental Efficiency (J. of Educ. Psychol., 1913, IV., 61-70), uncontrolled association, opposites, part-wholes, genus-species, digit-symbol and symbol-digit substitution, memory for concrete and for abstract words, memory of Marble Statue selection, (only boys' norms used for each). Pyle and Anderson combined by Whipple (_220_) two word-building tests (boys). Anderson as given by Whipple memory for letter squares. D. F. Carpenter, Mental Age Tests (J. of Educ. Psychol., 1913, IV., 538-544), substitution of colors in forms and of numbers in forms, perception time in marking A's, concentration, _i. e._, difference in time of last test under distraction, memory of pictures of objects, all tests devised by Carrie R. Squire. Stenquist (_54_), construction test. Sylvester (_191_), form-board test. [Illustration: FIG. 6. _Tests of the Development of Memory Processes. Medians at Each Age of the Central Tendencies of the Tests._] [Illustration: FIG. 7. _Different Types of Development. Medians at Each Age of the Central Tendencies of the Tests._] [Illustration: FIG. 8. _Forty Curves of Development. Distribution at Each Age of the Central Tendencies of the Tests._] In Fig. 6 curves A and B are Smedley's tests; curve C includes in addition Norsworthy's unrelated words, Pyle's memory for concrete and abstract terms, Anderson's letter-squares, Carpenter's memory for pictures, and Gilbert's for the time interval; curve E includes Pyle's two and Carpenter's two substitution tests; curve F includes Pyle's Marble Statue and Norsworthy's memory for related words and for sentences; curve S is Norsworthy's; curve D is the combination of these 17 tests.