48 K. S. LASHLEY AND L. E. WILEY 



1. The relation between extent of lesion and retardation in 

 maze learning is curvilinear and the error scores appear to be 

 a logarithmic function of the extent of lesion. 



2. It has been impossible to detect any influence of small 

 injuries in the archipallium or thalamus (when combined 

 with extensive cortical destruction) upon the maze scores. 



3. The portions of the lesions, asymmetrical with respect- 

 to the two hemispheres seem to contribute to the retardation, 

 as well as do the symmetrical portions. 



4. Lesions in all parts of the neocortex produce a marked 

 deterioration. Our data are inconclusive with respect to the 

 exact equipotentiality of the areas. 



The cases were divided into four equal groups, each of 

 which was trained on one of four mazes with 4, 8, 12, and 

 16 culs de sac. The normal and operated groups were com- 

 pared with respect to the relative difficulty of the four mazes. 

 The operated animals were markedly retarded in all mazes, 

 but the relative difficulty of the simple and complex mazes 

 was the same for them as for the normal controls. This con- 

 clusion applies to mazes in which difficulty is increased by 

 duplicating identical elements. The problem of relative 

 difficulty where qualitative differences are introduced remains 

 unsettled. 



LITEEATUEE CITED 



Boumann, L., and A. A. Grunbaum 1925 Experimentelle-psychologische Unter- 



suchungen zur Aphasie und Paraphasie. Zschr. f. d. ges. Neurol, u. 



Psychiat., Bd. 96, S. 481-538. 

 Cameron N. 1928 Cerebral destruction in its relation to maze learning. 



Psychol. Monogr., vol. 39, no. 1, pp. 1-68. 

 Carr, H. A. 1917 The alternation problem: a preliminary study. J. Animal 



Behav., vol. 7, pp. 365-384. 

 Fortuyn, A. E. B. D. 1914 Cortical cell-lamination of the brains of some 



rodents. Arch. Neurol. Psychiat., London, vol. 6, pp. 221-354. 

 Head, H. 1926 Aphasia and kindred disorders of speech. New York. 

 Henschen, S. E. 1927 Aphasiesysteme. Monatschr. f. Psychiat. u. Neurol., 



Bd. 65, S. 87-137. 

 Hunter, W. S. 1920 The temporal maze and kinesthetic sensory processes 



in the white rat. Psychobiol., vol. 2, pp. 1-17. 

 Lashley, K. S. 1917 A causal factor in the relation between the distribution of 



practice and the rate of learning. J. Animal Behav., vol. 7, pp. 139- 



142. 



