CANADA PORCUPINE 21 



will disturb the porcupines, provided the modification in any 

 way affects the cue by which they are learning. It would be 

 dogmatic to say that the experimenter has not made the porcu- 

 pines use their right hands when he used his right hand and 

 their left hands when he presented food with his left hand, but 

 if this has been the case while at the same time it was being 

 consciously guarded against, then the same thing, with the 

 inhibitions thrown off, and conscious encouragement added, as 

 would almost universally be operative in the case of the human 

 infant, is sufficient to account for. the peipetuation of right- 

 handedness once it is established as a human trait. The per- 

 sistence of the habit when formed in the human infant has 

 never been tested as rigidly as it has been in the animal. This 

 will be shown in the next paragraphs. The child of seven months 

 is no fit subject for experimentation sufficiently intensive and 

 extensive to break a motor habit of this character. It would 

 be more reasonable to conclude that in the case of the porcu- 

 pines there is a sense of balance with the environment, or, 

 maybe, a mere convenience which places the right hand in the 

 line of grasp of the right hand of the experimenter, and the 

 animal responds to that situation neither more nor less mechan- 

 ically than children do. There is a certain naturalness about 

 it all, which, in the initial stage, tips the balance toward sym- 

 metry with the environment without involving any large degree 

 of mentality and without presupposing any anatomical superi- 

 ority of bone, muscle, eye, or nerve.* 



At this stage the experiment was modified, and the records 

 of No. 3 will again be reported in detail. In the preliminary 

 work cabbage was fed altogether. Food was now changed to 

 carrot, cut in small pieces, and at the same time the porcu- 

 pine was forced to take it with his left hand, food being refused 

 when he extended his right hand though the experimenter still 



* Since the above was written the author has been interested in reading the 

 study " The Retina and Righthandedness " by Stevens and Ducasse. Psy. Rev., 

 Vol. XIX, No. 1, Jan., 1912. Those writers made experimental investigations 

 of the relative size of the perceived image on different areas of the retina. Their 

 results indicate that the "space sense" of the left side of the retina is greater than 

 that of the right side. They conclude as follows: " Those objects in the right 

 half of the field of vision, by appearing larger, attract the visual attention, which 

 in turn leads to grasping movements with the right hand." The theory would 

 be more readily accepted in this causal relation if it were known that this disparity 

 of the space sense was true of earliest infancy and was not itself induced by the 

 child's en\Tronment. 



