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j. JACOBS : Numerals have the further advantage that school-children are accustomed to take them down from dictation, and this leads us to deal with the modus operandi adopted in obtaining our results. It was necessary, in the first place, to adopt some uniform rate at which the dictation should be given, as the power of apprehension varied with the rate of utterance. A sound every half-second was found to be a convenient rate, and a little practice with a metro- nome beating twice a second gives the experimenter a sense of the proper interval. The repetition was in the first experiments oral, but afterwards was taken in written form. If possible, two sets of the series of sounds should be given, and the highest num- ber correctly reproduced is to be regarded as the limit which we wish to find, and which we term here the span. The reading should be in a monotonous tone, so as not to give any perceptible accent or rhythm, either of which, it appeared, assists the power of repetition in a considerable degree. The papers, when handed in, were marked with the names of the " subjects," to which it was found useful to add their ages and, if possible, their places in form. Early in the inquiry it became evident that the power of repro- ducing a number of sounds increased steadily with age. Our materials enable us to draw up the following Table, which clearly shows the increasing power of school-girls in mastering nonsense- syllables as they grow older : Age, .... 11 12 13 14 17 18 19 20 Number of " Subjec ts . 3 711 912 13 6 2 Average of Syllables, . 5'3 5'3 57 5'2 57 6'1 7'2 7'0 Here there is a distinct rise from 11 to 13, and from 17 to 19, and a marked progress in the whole series from 5-3 at 11 to 7*0 at 20. The same gradual increase of span is also shown in the following results for boys and girls of various ages in reproducing numerals and letters : BOYS. GIRLS. Age, 11 12 13 13 17 18 19 20 "Subjects," . 70 57 47 60 32 28 4 3 Av. of Numerals, 6'5 6'8 8-8 8'3 91 9'9 9'4 9'0 Av. of Letters, 5-5 57 6'9 7*3 87 8*8 8-1 S'O 1 1 These are summaries of results by different observers and under vary- ing conditions. Later on a more extended and trustworthy set of observa- tions were made on the girls of the North London Collegiate School, with the following results : Age, . . .8 9 10 11 12 13 14 "'Subjects, . 8 13 19 36 41 42 42 Av. of Numerals, 6-6 67 6'8 7'2 7'4 7'3 7'3 Av. of Letters, .6 7 6'6 4'6 6'5 67 67 The answers were here written down, not taken orally as in the cases tabulated above. The uniform reduction of span at the corresponding ages 15 16 17 18 19 72 66 50 30 14 77 8 8 8-6 8'6 7'4 7'9 7'3 8'2 7'9