7+6 



THE POPULAR SCIENCE MONTHLY. 



keep it from moving. A large screen is interposed between tlie 

 subject and tlie record to prevent him from indirectly seeing wliat 

 is going on. On the wall facing him, some eight feet distant, are 

 some small patches of color, the names of which he is asked to call 

 out. The colors are small enough to necessitate close attention in 

 their distinction, and the record of the hand, after the subject has 

 been employed in this way for a minute or two, is usually quite 

 significant. An average result is presented in Fig. 1. The hand 



moves clearly and directly 

 toward the wall where the 

 colors hang ; the move- 

 ment is at times halting 

 and uncertain, but its gen- 

 eral trend is unmistakable. 

 Moreover, the result can 

 not in general be antici- 

 pated, not alone because 

 there are marked differ- 

 ences between individuals 

 in the readiness with which 

 they will manifest invol- 

 untary movements, but 

 also because the intensity 

 of the attention and the 

 momentary condition of 

 the subject are imjDortant 

 and variable factors in 

 the result. With very 

 good subjects it becomes 

 quite safe to j^redict the 

 general nature of the re- 

 sult, and the different trac- 

 ings of the same subject 

 1 )ear a family resemblance 

 to one another. 



A more unusual but 

 very striking form of in- 

 voluntary movement is 

 shown in Fig. 2. As be- 

 fore, the subject's atten- 

 tion was fixed uj)on the 

 colors on the wall, but these were arranged in three rows, the 

 first being read from left to right, the second from right to left, 

 and the third from left to right again. The record plainly indi- 

 cates where the change of direction of reading took place ; the 

 correspondence between the movements of the hand and of the 



Fio. 2. — Readino Colors arranged in Three Rows. 

 Shows movement of the hand |)araliel with move- 

 ment of the attention. Time of record, 90 seconds. 

 The iirst line was read in this direction J, the sec- 

 ond in this J, tlie tliird in this J. At the turn from 

 the second to the third line the record is interrupted. 



