EXPEEIMENTS ON " PEEHENSION ". 77

Steady advance is shown on the average throughout this Table except in the highest ages of the girls, where, however, the num- bers are too small to allow us to draw any definite conclusions. The progress must, however, stop at some time, and the familiar fact of minds getting ' stale ' after a certain age suggests the pos- sibility that the increase in the span ceases with the increase in the bodily growth. The most noteworthy result of the table is ths sudden leap of two syllables in the cyphering powers of the boys between the ages of 12 and 13. This may be due to greater practice in arithmetic. At any rate it raises them above the average for the girls of the same age, though they hold the reverse position as regards letters. No conclusions can be drawn as to the relative spans of the two sexes at the age of 13, as the subjects were drawn from two entirely different grades of society, and in the case of the boys (who were of the Jews Free School, Bell Lane, ) x racial influences may have been at work in producing earlier maturity. If, then, the span increases normally with age up to a certain point, it follow? that in any class of the population, and in the population generally, below that age there will be a fixed number of syllables, letters and numbers which can on the average be seized after once hearing by persons of each age. This number can be determined by the means referred to above, and might easily form an addition to the usual items of anthropometric inquiries. If this were done we should obtain a standard span for the various ages and conditions just as we do for height, weight, &c., a standard relative and not absolute, but still enabling us to ascertain whether a boy or girl were above or below the average, and even the rate of growth in this particular. Another fact came out with equal clearness as our materials accumulated. This was that, as a rule, high span went with high place in form. Thus, selecting 30 boys of 12 years old out of a class and taking the average of their span as regards numerals, this was found to be 9'1 for the first ten, 8'3 for the next ten, and 7*9 in the remainder. In another class, also of 30 boys of the same age, the averages of the three sets of ten were in order 7 '6, 7'1 and 6 - 3 respectively. Eight girls of the same age, taken in their order in class, gave for the first four an average of 8-2 for numerals against 8*0 for the last four, while the span for letters remained constant. With 12 girls of 13 years of age the first six had an average span of 8*3 against 7*8 for the last six in the case of numerals, while for letters the two sets were again equal. But the generality of the relation comes out clearly in the following (of the girls) may perhaps be taken as a mark or even as a measure of the cerebral process involved in translating sounds into their visual symbols. 1 The experiments were made by Mr. Louis Cohen, one of the masters of the school.