IV. — On the Relation of Muscle Sense to Pressure Sense 



BY T. L. BOLTON AND DONNA L. WITHEY 



In the following pages are reported the results of some experi- 

 ments instituted with the purpose of studying more critically 

 than yet has been done the relations between muscle sense and 

 pressure sense, and furthermore of examining, incidentally at 

 least, both the physiological and psychological processes of per- 

 ceiving weight in general and the factors involved in discrim- 

 inating differences between two weights. Various aspects of the 

 perception of weight and of the discriminative process have been 

 most carefully studied by Miiller and Shuman,^ Martin and 

 Miiller- and others, but so far as we are able to find there has 

 been no study of the particular way in which muscle sense affects 

 discriminations by pressure, and no one has pointed out the phys- 

 iological processes involved in the perception of a weight and in 

 the process of discriminating one weight from another. 



How, then, do free lifting movements and the participation of 

 muscular reactions affect pressure discriminations of weight? 

 The difference threshold for pressure discriminations of weight 

 as determined by E. H. Weber, based upon a given probability 

 of correct judgments, and since confirmed by Fechner and others, 

 is about one-third of the stimulus; and the same threshold for 

 weights lifted with free arm movements has been variously stated 

 as one-tenth to one-fortieth. The ratio of J5:i6 for just ob- 

 servably different weights by the free or natural mode of lifting 



^Miiller and Schuman. C/bcr die Psychologischcn Grundlagcn dcr 

 Vergleichung gehobenen gcivichtc, Pfliiger's Archiv. f. d. ges. Physiologic, 

 1889, Band 45, S. 37 ff. 



"Martin und Miiller. Zur Analyse der Untcrscherds EmpHndhchkeit. 

 Leipzig, 1899. See also E. A. Hayden, Memory for Lifted JVcighls. Amer. 

 Jour. Psych., vol. 17, pp. 495-521. 



University Studies, Vol. VII, No. 2, April 1907. 



