May 8, 1896.] 



SCIENCE. 



685 



the "University, made an address reviewing 

 the work of the University in relation to 

 the social and political growth of the city. 

 The last speaker was President Eliot, who, 

 in the name of the universities of America, 

 congratulated Columbia University on its 

 setting commensurate with the worth of its 

 intellectual and spiritual influence. 



PSrCSOLOGIOAL NOTES UPON SLEIGHT-OF- 

 HAND EXPERTS. 



The determination of the influence of 

 special kinds of occupation and training 

 upon the delicacy, range and quickness of 

 sensory, motor and mental powers is an 

 important and interesting problem. Obser- 

 vations of this kind must first be directed 

 to the determination of the average capa- 

 bilities of average individuals and then be 

 extended by a study of the influences of 

 age, sex, heredity, training and a multitude 

 of other factors upon the growth and perfec- 

 tion of special powers. Last of all will 

 come the study of small, special groups of 

 persons and of the individual himself At 

 all times, however, an individual with ex- 

 ceptional powers in any direction is quite 

 certain to attract attention and arouse in- 

 terest; psychological tests made upon such 

 virtuosi are desirable, even if in indi- 

 vidual cases they suggest no very decided 

 conclusions. 



Having recently enjoyed visits at my 

 Psychological Laboratory from Messrs. 

 Hermann and Kellar, the widely-known 

 prestidigitators, I put together the results 

 of the series of tests to which they kindly 

 submitted. As the time at my disposal for 

 these tests was limited, I selected such as 

 might be supposed to be related to the 

 processes upon which their dexterity de- 

 pends, and such as seemed most likely to 

 yield definite results. 



Beginning with tests of tactile sensibility, 

 I determined the distance at which two 

 points of an aesthesiometer placed upon the 



forefinger of the right hand could be recog- 

 nized as two. This distance was for Mr. 

 Hermann 3.5 mm. and for Kellar 2.5 mm. A 

 comparable average result, obtained from a 

 considerable number of miscellaneous in- 

 dividuals, was about 2 mm., indicating a 

 somewhat coarse sensibility for the two 

 special subjects. The attempt to arrange 

 in their correct order a series of 5 weights 

 increasing by -^ of their weight was unsuc- 

 cessful in the case of Mr. Hermann, but was 

 successfully carried out by Mr. Kellar. The 

 attempt to arrange weights difliering by ^ 

 was entirely unsuccessful for both of them. 

 In a general series of tests, 92% of those 

 tested arranged the former series correctly, 

 and 66 % the latter. The weights were es- 

 timated by lifting them between thumb and 

 forefinger. A test of sensitiveness to tex- 

 tures was also made. The fingers were 

 passed across a surface composed of wires 

 wound closely side by side. Mr. Kellar was 

 tested with a series in which each surface 

 was \ coarser than its neighbor, and with 

 one in which the differences were only \. 

 He arranged the first correctly, but was en- 

 tirely mistaken in the arrangement of the 

 second. Mr. Hermann tried only the finger 

 differences which he also failed to arrange 

 properly. I next tested the same sensi- 

 bility by having the subject feel between 

 the thumb and forefinger, as in feeling the 

 thickness of paper, a set of single wires of 

 various calibres, mounted upright on wooden 

 blocks. In one series the differences were 

 f , in another i. Both Mr. Hermann and 

 Mr. Kellar succeeded in arranging both 

 series correctly, but this was also done by 9 

 out of 10 persons who were tested in the 

 same way. Still another form of tactile and 

 motor capacity was tested by requiring the 

 subject to arrange in order a series of bars 

 of varying length by passing the forefinger 

 across them. Both Mr. Hermann and Mr. 

 Kellar passed this test successfully in the 

 series varying by -^-^ of their average length; 



