Page:Mind (Old Series) Volume 11.djvu/387

 386 J. M. CATTELL : of experiments, determining the time the light reflected from a printed letter must work on the retina in order that it may be pos- sible to see the letter. These experiments show that there is a great difference in the legibility of the several letters ; out of 270 trials W was read correctly 241, E only 63 times. In this case the whole time was short, 1 to l-5<r, and the difference in the time for the several letters correspondingly small. When how- ever we determine the entire time needed to recognise the letter, we may expect to find the time considerably shorter for a simple and distinct symbol than for one complicated or easily confused with others, just as the time is shorter for a colour than for a letter. 1 The speech-organs as well as the hand were used in these experiments. Here however a slight complication is added, as we cannot be sure that a difference in the time for the several letters is to be referred only to the perception-time, it being pos- sible that the time needed to name the several letters or to register the different motions may be different. This difference in time can however only be very small, as the observer knew what letter he had to name, so there was no choice between different motions, as in the experiments to be considered in the next section of this paper. Tables XXII. -XXIV. (placed, with others, at the end of this paper) give the results obtained at different times, the motion being made both with the hand and the speech-organs. A shortening in the time through practice will be noticed in these Tables ; if we take Table XXIII., which contains the most determinations and times representing about the average of the three Tables, we find the perception-time for a capital letter of the size in which this is printed to be 119<r for B, 116 for C. The Tables contain the results of a great many experiments, but not enough to determine finally the time for the several letters ; if however the four series made with the hand on E and M are averaged together, we find that it took B 19, C 22<r longer to see E than to see M. The order for the five letters on which four series were made is M A Z B E, which (except the position of Z) agrees with the order of legibility established in the paper refenvd to. Similar determinations were made with the small letters, the results being given in Table XXV. It seems from this Table 1 I have not been able to determine accurately and finally the percep- tion-time for different alphabets and for the several letters. In these experiments the different letters cannot well IK- used in the same scries, and further in half the cases no mca.-ure.meiit is mail.-. As the difference in the times is small and the variation of the series not inconsiderable, a lar^e number of experiments must lie made before tin- difference in the time for the several letters can be determined with certainty. This is however not only a subject of scientific inteiv-t, but also of j^ivat practical impoitance ; it is to be ho] >ed that it will be thoroughly investigated by independent ex- perimenters.