Febeuaky 5, 1897.] 



SCIENCE. 



221 



THE LAW OF SIZE-WEIGHT SUGGESTION. 



In 1893 Dr. J. Allen Gilbert, working under 

 my direction, obtained measurements on the 

 size-weight illusion. A cylindrical block of 82 

 mm. diameter and of 55 g. weight was com- 

 pared with a series of blocks of 35 mm. di- 

 ameter but of various weights. The subject 

 first lifted the large block, and then picked out, 

 by lifting, that block of the series which ap- 

 peared to be equal in weight to the larger one. 

 The error in weight thus made was due to the 

 suggestive effect of the difference in size. 



These were the first measurements made on 

 the size-weight illusion (' Studies from the 

 Yale Psychological Laboratory,' 1894, II., 

 43).* 



The problem was then investigated in detail 

 by Dr. C. B. Seashore (' Studies from the Yale 

 Psychological Laboratory,' 1895, III., 1). TwS 

 sets of cylindrical blocks were made. Set A 

 varied in diameter, but had a uniform weight 

 of 80 grams. Set B varied in weight, but were 

 of a uniform size of 43 mm. The subject, lift- 

 ing the block between thumb and finger, was 

 requested to select for each block in Jt a block 

 of equal weight in B. In this way the effect of 

 size on apparent weight was determined. 



In the ' Studies' for 1894 1 had already pointed 

 out the possibility of establishing the law of 

 suggestion in such experiments. I now find it 

 possible to do so on the basis of Dr. Seashore's 

 work. 



h 

 The curve conforms closely to the form y^ — 



X 



which is the equation of a hyperbola referred to 

 its asymptotes as axes with the constant h de- 

 pending on the nature of the experiment. The 

 actual measurements differ from the values re- 

 quired for this formula only by a small quan- 

 tity z^f(x), which expresses tha apparent in- 



* Professor Binet has called attention to the fact 

 that he anticipated Gilbert by one month in measur- 

 ing suggestion by his experiments on the length of 

 lines. This, however, was quite a different form of 

 suggestion. If the question is to be raised as to the 

 first measurements of suggestion in any form, I am 

 justified in claiming priority over Binet by the ex- 

 periments briefly indicated in the Educational Review, 

 1893, v., 61. 



— d. 



crease in the diameter of the block due to the 

 contrast with the constant length.* 



If the blocks of the B series be made of the 

 constant diameter c and those of the A series of 

 the constant weight d, and if we denote by a 

 the difference in size acting as a suggestion, by 

 i the resulting illusion and by fc a constant de- 

 pending on the nature of the experiment, then 

 we have the general law 

 fc 

 s -\- c 



which can be called the law of size- weight sug- 

 gestion. Thus, in the first set of experiments c 

 was 43 mm., d was 80 g., and k was determined 

 by the facts : that the blocks were looked at 

 while lifted; that the subjects were ignorant 

 of the illusion, etc. In the other sets of ex- 

 periments by Dr. Seashore k took other values. 

 E. "W. Scripture. 



Yale University, 



January 1, 1897. 



SCIENTIFIC LITERATURE. 

 Bound the Year: A Series of Short Nature-Studies. 



Professor L. C. Miall, F. R. S. Pp. 290. 



Macmillan & Co. Price, $1.50. 



The book is precisely what its title promises. 

 Its author is a cultivated and observant scholar 

 who loves nature and records her various 

 phases after the manner of the old-time natur- 

 alist, though rectified by new-time science. It 

 reminds one of White's Natural History of 

 Selborne, and the author's familiarity with that 

 classic has unconsciously led him into the ami- 

 able and homelike style of White, and this isto 

 the merit of the book. He evidently has little 

 sympathy for much that goes for modern nat- 

 ural history to-day. He says "natural history 

 is being choked by unassimilated facts mechan- 

 ically compiled by men who have apparently 

 ceased to think about Nature. Hence a profuse 

 and growing literature of the most melancholy 

 description, dry, marrowless, useless. We re- 

 cord and record till our catalogues grow too 

 voluminous for storage and too stodgy for the 

 toughest appetite." The subjects discussed 

 cover a wide range ; we are led from Insects 



* The exact values of z have not yet been determined 

 experimentally. The results of a special investiga- 

 tion will appear in the ' Studies from the Yale Psycho- 

 logical Laboratory. ' 



