EFFECT OF LENGTH OF BLIND ALLEYS ON ^L\ZE LEARNLNG 41 



kinds of stimuli operate, directly or indirectly, toward the learning 

 to avoid entering cul de sacs'" 



That the rat is not wholly blind has been demonstrated in 

 a number of cases, ^o but there is no clear evidence to show that 

 the presence of such visual factors as are possible to the rat 

 could operate on the principle of frequency, recency, or intensity, 

 or all combined, in such a manner as to eliminate the impulses 

 to enter the cul de sacs under the conditions of the present prob- 

 lem. They might, of course, aid the rat in getting to the food 

 at any one time, but how could they operate toward cutting 

 short the random processes in successive trials, i.e., in bringing 

 aVjout what is called learning? A brief review of the work on 

 visual controls in the rat's behavior is to be found in Miss Vin- 

 cent's paper. Waugh found-' that though the mouse could 

 perceive the distance of objects " within a range of 15 cm.," 

 it nevertheless seemed not to make use of the " visual percep- 

 tion of depth " in getting past two partitions each from oppo- 

 site sides reaching half way across the problem box, the one 

 being nearer than the other. 



In the present experiment, it will be recalled, the interior of 

 the maze was stained black, and even if it be granted that the 

 rat could see the ends of some of the shortest cul de sacs there 

 would be but little difference in the visual stimuli between the 

 " blind " and the open alleys, in as much as both were obstructed 

 alike in the further end and the side opening of the latter was 

 not directly visible. Differences in brightness would be irregular 

 and but slight, as the room was lighted from three sides — south, 

 west, and slightly from the north — and an electric light was 

 directly over the maze. It should be said that no difference 

 in behavior between the rat blind in the left eye — No. 20 — and 

 the other rats was noticeable though the experimenter kept 

 watch for such difference. More careful visual controls are of 

 course desirable. 



But the real question is how any stimulus, visual or otherwise, 

 must operate together with other stimuli so as to inhibit 

 unsuccessful acts and to cause to survive those acts which bring 



2" See Richardson, Florence. A Studv of the Sensorv Control of the White 

 Rat. Psychol. Mori., Ser. No. 48, 1909. \incent, Stella B. The White Rat and 

 the Maze Problem — I. The Introduction of a Visual Control. Joitr. Animal 

 Behav., 19 15, 5, 1-24. 



-' Waugh, K. T. The Role of Vision in the Mental Life of the Mouse. Jour. 

 Camp. Neurol, and Psychol, 1910, 20, 549-599. 



