THE ORIGIN OF RIGHT-HANDEDNESS. 



609 



no preference for either hand in reaching straight before her 

 within easy reaching distance (ten inches) ; but she was right- 

 handed to a marked degree during the same period as regards 

 movements which required effort or strain, such as grasping for 

 objects twelve to fifteen inches distant. The left hand was used 

 in only five cases as against seventy-four cases of the use of the 

 right hand ; and further, all these five cases were twelve-inch dis- 

 tances, the left hand being used absolutely not at all in the forty- 

 five cases at longer distances. 



In order to test this point further, I varied the point of expos- 

 ure of the stimulus to the right or left, aiming thus to attract the 

 hand on one side or the other, and thus to determine whether the 

 growth of such a preference was limited to experiences of conven- 

 ience in reaching to adjacent local objects, etc. The result appears 

 in Table IV : 



Table IV. 



This table shows that deviation to the left in front of the body 

 only called out the right hand to greater exertion, while the left 

 hand fell into still greater disuse. This seems to show that dex- 

 trality is not derived from the experience of the individual in 

 using either hand predominantly for reaching within the readiest 

 range of that hand. 



Proceeding upon the clew thus obtained i. e., that a stronger 

 effort brought a preferential hand reaction a clew which seems 

 to suggest that the hand preference is a function of the relative 

 strength of the influence of the eye stimulus, I introduced hand 

 observations into a series of experiments on the same child's per- 

 ception of the different colors which I was making at that time, 

 thinking that the color stimulus which represented the strongest 

 inducement to the child to reach, might have the same effect in 

 determining the use of the right hand as the increased distance in 

 the experiments already described. This inference is proved to be 

 correct by the results given in Table V : 



Table V. 



Color stimulus, j Hand Right. Left. 



10 to 15 inches ( Number of cases 86 2 



Both. 



j-May 



23d to June 19th. 



It should be added that in all cases in which both hands are 

 said to have been used, each hand was called out with evident in- 



VOL. XLIT. 46 



