USE OF HANDS BY MONKEYS 141 



The monkeys used in this work were being trained previous 

 to certain operative procedures on the occipital lobes. 1 They 

 had been used in a previous investigation, 2 in which they had 

 been fed from the front, sides, and bottom of the cage, and in 

 which no attempt was made to have them use a special hand. 

 During this latter investigation no observations were made of 

 a preferential use of the hands. At the time the use of the 

 hands was observed and the observations recorded, the animals 

 were kept in cages 114 cm. high, 90 cm. wide, and 58 cm. deep. 

 The front and right hand ends of the cages were covered with 

 chicken wire, of one and one-half inch mesh. The top, bottom, 

 the back and the left side were boarded. Within the cage there 

 was a shelf 30 cm. wide jutting from the back of the cage at a 

 height of about 45 cm. and extending the width of the cage. 

 The animals were not handled and the environment, with the 

 exception of the presence of the experimenter, was fairly con- 

 stant during the progress of the experiments. Food and water, 

 other than that used in the experiments were pushed through 

 or under the wire front of the cage and the animal took of them 

 when and as much as he wished. At the time of making the 

 observations the animals were partly fed in the morning and 

 the observations and tests made in the afternoon, or vice versa. 



In performing the tests, the animal was in the cage, usually 

 sitting upon the shelf. A glass plate, 12.5 by 18 cm., was 

 arranged to hang horizontally on the wire netting of the cage, 

 and was movable so that it could be placed upon any part of 

 the front or right hand sides, i.e., those covered with the 

 chicken wire. The food was placed upon the glass plate, this 

 was arranged on the wire netting, and the experimenter moved 

 away about a meter's distance. The animal, which usually 

 during the preliminary arrangements sat at the farthest end 

 of the cage, moved forwards and took the food. During the 

 tests two pieces of food were presented, one of which was sweet, 

 the other bitter. The arrangement of the relative positions of 

 the two pieces of food was constantly changed so that half 

 of the times the bitter bread was on the animal's right and 

 half of the times on the left. At times the two pieces were 



1 For details see Franz. The Occipital Lobes. Psychol. Review Monog. No. 56, 

 1911. 



2 Shepherd. Some Mental Processes of the Rhesus Monkey. Psychol. Review. 

 Monog. No. 52, 1910. 



