Page:Mind (Old Series) Volume 11.djvu/66

 V. EESEAKCH. STUDIES OF RHYTHM. By Prof. G. STANLEY HALL and JOSEPH JASTROW. Psychophysical Laboratory, Johns Hopkins University, Baltimore. IN a series of observations undertaken in the psychophysical rooms of this University by Mr. J. M. Cattell, single letters of 1-75 diopters were cut out of a book of Snellen's optotypes and pasted in horizontal rows 1 cm. apart on a white background around the revolving drum of a Ludwig kymograph. Care was taken that there should be no repetition of letters or of sequences and that the letters should not spell or suggest any words. These letters were viewed at a constant distance of easy accom- modation through a screen placed as near as possible to the drum, by means of a slit 1 cm. wide and of variable horizontal length. The revolution of the drum gave thus the 'conditions of normal reading except that instead of the eye moving along the line of letters the line moves in the opposite direction across the field of vision, the eye remaining stationary. By varying the width of the aperture or slit, the rate of movement of the drum and the size of the letters, several interesting determinations elsewhere to be reported were made. One striking result, some- what incidental however to the main object of these observations, was that under the same conditions the names of the letters could be pronounced more rapidly than the letters could be counted. With the slit open, e.g., 1 cm., exposing thus one letter at a time, the average time of many records each in nine different persons was O248 and O2S3 sec. per letter at the most rapid possible rate of pronouncing the names of and of counting series of fifty letters respectively. As in naming letters we can foresee no sequence but only the interval, while in counting we foresee the succeeding number-names and have only to match a series of visual and an established series of motor impressions, this time-relation was not foreseen. In a later series of obser- vations yet unfinished, Mr. G. T. Kemp counted linear sets of from three to thirty black squares pasted upon strips of white pasteboard. The eyes were brought before a long slit closed by the arm of a long horizontal lever held in position by a magnet, while the attendant placed any slip in the slide where it was instantly seen as (after an avertissemenf) the lever fell. The ob- server had to press a key as soon as the counting was finished, and the attendant only to set the Hipp-chronoscope and record the results. As the whole series to be counted was seen from the first and the position of the first spot to be counted was predetermined, and as all erroneous results were excluded by the recorder and all