86 



BRAIN MECHANISMS AND LEARNING 



whole, this experiment also had little effect, conhrming the tests with the 

 reversed song and suggesting even more strongly that the natural training 

 which the bird had already received by the time it has reached the fnst 

 winter moult has equally been sufficient to prevent it from learning after- 



FiG. 7 

 Re-articulatcd model with 'end in middle'. 



wards the rather large abnormalities characteristic of these re-articulated 

 songs. 



When we come to similar experiments with hand-reared birds, very 

 different results are obtained. It was found that a hand-reared visual isolate 

 can be taught features of a normal song from the tape by being exposed to 

 it during November only of its tu'st winter for a period of lo days. Figs. 5 



Fig. 8 

 Song of hand-reared auditory isolate B/BkP after having been exposed 

 to this model for 12 days January-February and 12 days February-March. 

 March 25th, 1958. 



and 6 give the two songs developed in 1956 by such a bird treated in 1955. 

 The first song shows clearly the influence of the 'tutor' in that it has three 

 phrases otherwise unknown in the hand-reared isolate, having a clear 

 stepwise descent but no end-phrase. The second song is of the isolate type 

 plus two end-notes. These experiments thus produce evidence that tutor- 



