USE OF THE HANDS IN THE RHESUS MONKEY 



181 



of the experimenter, using the homologous hand in only 55% 



of the cases. 



TABLE 1 



Preferential Use of the Hands Under Different Environmental 

 Conditions in Two Rhesus Monkeys 



Conditions of Test 



Hand used . 



Monkey in cage, taking food 



from — 

 a — experimenter's right hand . . . 



b — experimenter's left hand 



c — floor of cage 



d — table before cage 



Monkey on floor outside of cage, 



taking food from — 

 e — experimenter's right hand . . . 



f — experimenter's left hand 



g — floor of room 



All trials 



Monkey No. 1 



Number 



of cases 



in which 



each hand 



was used 



R 



146 

 46 

 23 

 59 



386 



3 



133 



796 



102 



155 



243 



41 



47 

 164 

 192 



944 



Per cent 



of cases 



in which 



each hand 



was used 



R 



59.7 



22.0 



8.6 



59.0 



89.1 



1.7 



40.9 



45.7 



40.3 

 78.0 

 91.4 

 41.0 



10.9 

 98.3 

 59.1 



54.3 



Monkey No. 2 



Number 



of cases 



in which 



each hand 



was used 



R 



264 

 174 

 120 

 200 



158 

 60 

 30 



1006 



70 



42 



57 



4 



40 

 46 



267 



Percent 



of cases 



in which 



each andh 



was used 



R 



79.1 

 80.5 

 67.2 

 98.0 



95.2 

 60.0 

 39.4 



79.4 



20.9 



19.5 



32.8 



2.0 



4.8 

 40.0 

 60.6 



20.6 



A like predominance in the use of the hands was found in 

 reactions of defense. With the monkeys fastened in the middle 

 of the floor the experimenter touched them lightly on top of 

 the head with the tips of the ringers of his right hand. The 

 monkeys reacted to this by striking at his hand or by attempting 

 to grasp and bite it. The number of times in which each of the 

 two hands was used in warding off the touch is shown in table 2. 

 Number 2 was as markedly right-handed in this as in his food- 

 taking reactions. No. 1 again appeared to be left-handed, but 

 only to a slight extent. 



The predominant use of the hands seemed associated with the 

 positions assumed by the monkeys when kept alone in different 

 cages. They ordinarily sat in one of the rear corners of the 

 cage and the corner chosen was usually that which gave the 



