60 K. S. LASHLEY 



A. The question of prime importance for habit theory is that 

 of the existence of anatomical divisions of the nervous system to 



l^which the function of learning is restricted. The discovery of 

 such a region would give an opportunity for the study of the 

 r61e of finer structural differentiations, but there is no real 



r evidence that any such specialization exists. The evidence 

 advanced in support of the contention that the cerebrum of 



I mammals is the sole seat of the learning process is this : 



1. Invertebrates, lacking a cerebrum are incapable of asso- 

 ciative memory (Loeb, '00). This argument was advanced 

 before many tests of lower animals had been made. The demon- 

 stration of complex learning in all phyla above the coelenterates 

 annuls it. 



C2. Total destruction of the cerebrum is followed by the loss 

 >f most of the learned reactions of the organism. The observa- 

 tions of Flourens, Schrader, Goltz, Rothmann, and many others 

 establish this beyond a doubt. But in no case have the obser- 

 vations upon decerebrate animals been sufficiently detailed to 

 N prove that all habitual acts are abolished by the operation. 

 The average habitual acts observed by investigators have been 

 of a complex type requiring tremendously complex coordinations 

 of reactions to kinesthetic and external stimuli and no data 

 are available upon the persistence of simple conditioned reflexes. 

 The experiments of Rothmann (cited below) show either the 

 retention of some habits after complete decerebration or their 

 reacquirement after the operation: in either case a strong argu- 

 ment against the limitation of learning to the cerebrum. Lashley 

 and Franz ('17) found that simple habits were retained by the 

 rat after destruction of very large portions of the cerebrum, 

 embracing all except the temporal and basal portions. Finally 

 Ihe experiments reported in section V of this paper show that 

 a simple habit may be retained after the destruction of any given 

 third of the cortex. 



3. The formation of habits is not possible in the complete 

 absence of the cerebrum. In practically every case this con- 

 clusion has been advanced without any serious attempt to train 

 the animals, on the basis of the general impression of stupid- 



