194 RECORDS. 



H. R. Marshall, Primary and Secondary Presentations. 



Read by title. 



Summary of Papers. 



Dr. Franz, of Dartmouth Medical College, presented an 

 account of an attempt to determine by physiological experi- 

 ments whether or not the so-called motor areas are also sensory 

 in function. Cats were used in the investigation, and the results 

 indicate that in these animals the motor cortex has also certain 

 sensory functions. It was not determined with what sensory 

 processes the areas are concerned, but results of clinical obser- 

 vations made it appear probable that the center for muscle sense 

 is there located. 



Dr. Yerkes, of Harvard University, stated that inasmuch as 

 the degree of constancy of reaction-times differs for different 

 species, individuals, conditions of the individual, modes and 

 intensities of stimulation, it is clear that variability is an impor- 

 tant quantity in the analysis of reactions, which should make 

 possible the quantitative estimation of the influence of the vari- 

 ous factors which play a part in determining the time of reaction. 



The mean or average variability is generally determined in 

 recent studies of reaction time, but of far more importance for 

 comparative work is what may be known as the relative vari- 

 ability. This quantity is an index of the variability, which 

 gives not the absolute variableness of the reaction time, but the 

 ratio of the variability to the time of reaction. For reaction 

 times, which are symmetrically distributed about a mode, the 

 relative variability may be gotten from the formula 



mean variability x lOO 

 mean 



In case of asymmetrical distribution Pearson's formula for 

 obtaining the coefficient of variability should be used. 



Examination of reaction time statistics in which the variability 

 is given indicates that the relative variability, as well as the 

 time of reaction and the mean variability, decreases with increase 

 in the strength of the stimulus. For electric stimulation this 

 appears to be true from the threshold intensity to that which 



