726 



SCIENCE. 



[N. S. Vol. XVIII. No. 460. 



through 360 degrees and was divided so that 

 the ilhision for each of the long lines was de- 

 termined without reference to the next long 

 line. It was found that the illusion is not the 

 result of equal deflections in opposite direc- 

 tions of the neighboring lines. In some cases 

 one of two neighboring lines is not deflected 

 at all, or even in a direction opposite to that 

 usually assumed. The important deflection is 

 in every second long line. Rotation through 

 various angles shows that there are four posi- 

 tions in which deflection is great, four in 

 which it is small. 



Statistics of American Psychologists: Pro- 

 fessor J. McKeen Cattell, Columbia Uni- 

 versity. 



Professor Cattell described the methods he 

 has employed to select 1,000 American men of 

 science for scientific study. Among about 

 4,000 scientific men, there are about 200 psy- 

 chologists. The methods by which they were 

 arranged in the order of merit were explained, 

 and the possibility of measuring degrees of 

 scientific merit by the positions and probable 

 errors was discussed. Some statistics were 

 then given in regard to the academic origin, 

 course and distribution of the psychologists. 

 They were educated at 76 different colleges, 

 this large dispersal indicating that in general 

 psychologists are not greatly influenced by the 

 institutions at which they study. The num- 

 bers who pursued graduate studies at different 

 institutions were: Berlin 35, Leipzig 35, Co- 

 lumbia 31, Clark 31, Harvard 30, Cornell 25, 

 Yale 16, Johns Hopkins 13. Of the 200 psy- 

 chologists, all but eight are engaged in teach- 

 ing or administrative educational work, being 

 distributed among 77 institutions. Statistics 

 were also given in regard to publications, from 

 which it appears that the United States con- 

 tributes about one seventh of the more im- 

 portant publications, leading in experimental 

 psychology. The paper will be published in 

 the Atnerican Journal of Psychology. 



The Participation of the Eye Movements in 

 the Visual Perception of Motion: Professor 

 Raymond Dodge, Wesleyan University. 

 Photographic registration of the eye move- 

 ments has exposed the poverty and inaccuracy 



of all introspective data with respect to their 

 number, velocity and amplitude. While it 

 shows that, even if our consciousness were full 

 and exact in all three respects, it would be 

 either useless or misleading as a datum in the 

 visual perception of motion. 



Every pursuit movement of the eyes is a 

 definite muscular reaction to retinal stimula- 

 tion. As such it is evidently conditioned both 

 in direction and in velocity by some definite 

 characteristics of the stimulus which occasions 

 it. Since its accuracy can never transcend 

 the accuracy of the data on which it occurs, 

 it follows that the kinesthetic factor from a 

 reactive pursuit movement could never correct 

 nor materially augment the data furnished by 

 the stimulus. 



Moreover, the reaction of the eye involves 

 a long- reaction interval, about 160-170 a-. 

 This suggests both the relative unimportance 

 of the actual motor response and a consider- 

 able elaboration of the sensory data in what 

 seems like a simple reaction. But any reac- 

 tion interval at all renders it impossible for 

 the actual eye movement to parallel the move- 

 mept of the object of interest either in velocity 

 or in amplitude. 



Experimental verification of the above takes 

 two forms : Whenever all other sensory data 

 for the perception of motion are suppressed, 

 except the hypothetical kinesthetic factor, 

 there is no immediate perception of motion. 

 And whenever the former are distorted by eye 

 movements, the appearance of motion is re- 

 spectively decreased or increased, entirely with- 

 out correction by kinesthetic data. 



On the Horopter: Dr. Geo. T. Stevens, New 



York City. 



A horopter will be formed when the two eyes 

 are so adjusted as to enable the image of the 

 point fixed to be located exactly at the maculas 

 of the two retinas. It follows that horopters 

 succeed each other in endless variety and with 

 amazing rapidity. With every glance a new 

 horopter is developed. Two tenets constitute 

 the essential foundation for the doctrine of the 

 horopter the theory of actually horizontal and 

 actually vertical meridians of the retinas and 

 a doctrine of corresponding points. 



