THE ACQUISITION OF SKILL IN ARCHERY. 109 



at intervals of 2 minutes, or in each case as soon as the preceding shot had been 

 measured and recorded. Twelve shots were fired thus each day for 30 days. 

 The subjects had no opportunity to observe each others' methods of shooting 

 from a distance of less than 40 yards. Discussion of methods of shooting was 

 prohibited, but not with perfect success. The result of each man's practice 

 was posted daily and for group B (page 111) a prize of $5 was offered to 

 the subject making the best score on the greatest number of days. 



For the continuation of the work in Baltimore a safer and more convenient 

 range was necessary. A plot of open ground, 40 yards in length by 8 in width, 

 was laid out and the buildings shown in plate 8, figures 1, 2, and 3, were put 

 up at opposite ends of this. The small shed (figure 2), which serves to pro- 

 tect and isolate the subject, is 12 feet high and 12 feet wide by 8 feet deep. It 

 is equipped with racks for arrows, bows, etc., and a small telescope for use in 

 rifle practice. The target shed is somewhat larger, 14 feet high by 12 by 12 

 feet (plate 8, figures 1 and 3). Three feet back from the open front of this shed 

 is a pile of baled straw, packed tightly from the floor to the roof. The space 

 behind this straw partition is used for the storage of extra equipment. The 

 front of the shed is provided with large swinging doors, padded on the inside 

 with heavy quilted canvas mats. When these are opened, as in the photo- 

 graphs, a surface 14 by 24 feet is exposed, which will catch and hold the arrows 

 wherever they strike. The 4-foot straw target is mounted in the center of 

 the baled straw and a 10-inch paper bulls-eye marks the center of this. Plate 

 8, figure 1, shows the appearance of the target-shed from the opposite end 

 of the range. 



In the main experiment rifle practice was used as an index of the relative 

 ability of the subjects under the same conditions of practice. An efficient 

 single-shot air-rifle was used at a range of 40 yards. The 4-foot steel-faced 

 target used with this is shown in plate 8, figure 3. A constant supply of 

 paper targets was provided, a separate one being used for each subject's daily 

 practice. The entire equipment could be swung out of the way readily in 

 preparation for arrow practice. As the bullet holes in the paper are not 

 clearly visible at 40 yards it was necessary for the experimenter to watch the 

 target through a telescope and report the position of each shot to the subjects. 



COMPUTATION OF AVERAGES AND COMPARISON OF INDIVIDUAL 

 AND GROUP RECORDS. 



A series of records of shots with the bow or rifle invariably shows a great 

 range in the accuracy of the shots, even in the case of subjects who have 

 acquired a considerable degree of skill. With increasing skill the range of 

 variation decreases, but the relative amount of variation as measured by the 

 coefficient of variation remains practically constant. This is illustrated by 

 the record of one subject given in table 33. 



Some of this variation may be the result of the learning process itself (the 

 successive trial of different methods), but the greater part of it is certainly due 

 to chance external agents, such as variations in the strength of the wind, 

 weight of the arrows, tightness of the nock on the string, tension of the bow, 

 temperature, and extent of fatigue. As a result the average of any small 

 number of shots does not give a fair measure of the skill of the individual, and 

 the use of such averages as a measure of the initial and final accuracy and 

 amount of improvement does not lead to trustworthy results. 



