CORTEX AND CORPUS STRIATUM 99 



striatum and cerebral cortex are independent varia- 

 bles. When we compare the behavior of these animals 

 we see that innate and habitual behavior patterns 

 may be very greatly elaborated without correspond- 

 ing enlargement of capacity for rapid learning by 

 experience and intelligent types of behavior. We see 

 that amplification of innate and stereotyped behavior 

 goes hand-in-hand with enlargement of the thalamus 

 and subcortical parts of the cerebral hemispheres; 

 increase in capacity for rapid learning, memory, and 

 individual initiative is correlated with enlargement 

 and diversification of structure in the cerebral cortex 

 (Herrick, 1924, pp. 211, 270). 



From these observations and others that might be 

 mentioned it is clear that in birds the apparatus serv- 

 ing most of the established behavior patterns lies in 

 the thalamus and corpus striatum. The feebly devel- 

 oped cortex influences these behavior patterns but is 

 not essential to most of them. The cortex is essential 

 to the synthesis of the lower reflexes into certain types 

 of adjustment to external events and it exerts some 

 sort of a dynamogenic effect. Observation of de- 

 corticated birds in more varied situations than are 

 possible in small laboratory cages would probably 

 show greater deviations from normal behavior than 

 appear under the conditions described. Yet these 

 cortical influences at the most doubtless play a 

 relatively small part in the bird's total behavior. 



The birds represent a divergent line of evolution, 



