104 K. S. LASHLEY 



definite areas corresponding to the sensory projection areas of 

 higher forms and what the relation of these to habit-formation 

 may be. 



Such data will be of value also for the elucidation of another 

 problem. In his work on the frontal lobes Franz was inclined 

 to take the view that they acted as an association area, that they 

 were functional in learning because it was learning and not merely 

 because they are the normal projection areas for some group of 

 afferent or motor impulses. His experiments dealt only with 

 various types of latch-boxes, the habits for all of which probably 

 have a kinaesthetic foundation. If his view is correct, the de- 

 struction of the frontal lobes should result in the abolition of 

 any complex, recently formed habit. If, on the contrary, the 

 frontal lobes serve simply as a projection area, some sensory 

 habits should be found which would survive their destruction 

 and be eliminated by injury to other parts. 



With these questions in mind I took up the study of a visual 

 habit; discrimination between light and darkness. 



Apparatus and methods 



For setting up the habit a Yerkes' discrimination box of the 

 customary form was used. (The particular box has been figured 

 by Dodson, '17). The box offers a choice of two alleys and at 

 the end of each alley a circular, translucent stimulus plate was 

 fixed. In each trial one of these was illuminated, the other dark. 

 A number of normal animals were trained to go toward the il- 

 luminated plate and to avoid the dark one. No attempt was 

 made to restrict the stimulus to the plates and it is probable that 

 the animals reacted to the general illumination of the alleys 

 (Lashley, '12). Precautions were taken, however, to insure that 

 the reaction was to the visual stimulus. I have discussed the 

 control of visual stimuli extensively in other papers ('12 and '16) 

 and need not review the controls here. 



The animals were given 10 trials per day (food with the posi- 

 tive, no food with the negative stimuli) and training was con- 

 tinued until errorless records were obtained on two successive 



