6io THE POPULAR SCIENCE MONTHLY. 



dependence of the other, both about the same time, and both car- 

 ried energetically to the goal. In many other cases in which either 

 right or left hand is given in the tables, the other hand also moves, 

 but in a subordinate and aimless way. There was a very marked 

 difference between the use of both hands in some cases, and of one 

 hand followed by, or accompanied by, the other in other cases. It 

 was very rare that the second hand did not thus follow or accom- 

 pany the first ; and this was extremely marked in the violent 

 reaching for which the right hand was mainly used. This hand 

 was almost invariably accompanied by an objectless and fruitless 

 symmetrical movement of the other. 



The results of the entire series of experiments on the use of the 

 hands may be stated as follows, mainly in the words in which 

 I reported them summarily some time ago : * 



1. I found no trace of preference for either hand as long as 

 there were no violent muscular exertions made (based on 2,187 

 systematic experiments in cases of free movement of hands near 

 the body : i. e., right hand, 577 cases ; left hand, 568 cases ; a differ- 

 ence of nine cases ; both hands, 1,043 cases ; the difference of nine 

 cases being too slight to have meaning). 



2. Under the same conditions the tendency to use both hands 

 together was about double the tendency to use either (seen from 

 the number of cases of the use of both hands in the statistics given 

 above), the period covered being from the child's sixth to her tenth 

 month inclusive. 



3. A distinct preference for the right hand in violent efforts 

 in reaching became noticeable in the seventh and eighth months. 

 Experiments during the eighth month on this cue gave, in 80 cases, 

 right hand, 74 cases ; left hand, 5 cases ; both hands, 1 case. This 

 was true in two very distinct classes of cases : first, reaching for 

 neutral objects (newspaper, etc.) at more than the reaching dis- 

 tance ; and, second, reaching for bright colors at any distance. 

 Under the stimulus of bright colors, from 86 cases, 84 were right- 

 hand cases and 2 left-hand. Right-handedness had accordingly 

 developed under pressure of muscular effort in the sixth and 

 seventh months. 



4. Up to this time the child had not learned to stand or to 

 creep ; hence the development of one hand more than the other is 

 not due to differences in weight between the two longitudinal 



* Science, xvi, October 31, 1890; discussed by James, Science, November 8, 1890, by 

 Dr. J. T. O'Connor, ibid., xvi, 1890, p. 331, and by myself, ibid., xvi, November 28, 1890. 

 The report is quoted in full in Nature, November 13, 1890, and in part in the Illustrated 

 London News, January 17, 1891. See also Ebbinhaus's Zeitsch. fiir Psychologic, ii, 1891, 

 p. 239 ; Wilson, The Eight Hand: Left-handedness, pp. 128-131 ; Revue Scientitique, 1891, 

 ii, p. 493; discussed by Mazel, Revue Scientifique, 1892, i, p. 113. Both writers in the last- 

 named journal cite these experiments wrongly as Wilson's. 



