90 BRAIN MECHANISMS AND LEARNING 



between songs of between 6 and 20 seconds, (c) tonal quality (though this 

 last may have been learned by the experience of the bird of the qualities 

 of its own voice). The readiness with which the bird learns to divide its 

 song into three sections and learns to attach a simple flourish at the end as 

 an appropriate termniation shows that there must be an imperfectly 

 inherited tendency to respond to, and perform, tlie features of the normal 

 song as soon as the singer is stimulated by hearing another bird. Such an 

 inherited tendency would explain the basic similarity of the songs of the 

 species throughout its range. 



In conclusion, I believe that recent studies of bird behaviour have added 

 a considerable body of evidence in support of the view, now being 

 advanced from many quarters (sec Thorpe & Zangwill, i960) that in 

 regard to both learned and innate behaviour patterns the organism is to be 

 regarded as 'searching' largely for cues and stimuli, consummatory 

 situations in fxct, rather than for the release of consummatory acts. This 

 is to say that the 'goal' of the behaviour is not solely or even primarily the 

 discharge of a specific motor-nicchanism but the achievement of a 

 specific sensory stimulation. Moreover, in this connection we must 

 remember that the animal perceives its own consummatory acts primarily 

 through its own interoceptors and proprioceptors, and that in the majority 

 of cases at least it is again a special pattern of sensory stimulation, a re- 

 afference, which is the effective reward and not simply the general level of 

 well-being or activity resulting from the concomitant adjustment of 

 nutritional or endocrine balance. 



GROUP DISCUSSION 



Magoun. 1 am trying to relate this behaviour to mechanisms ot the brain. It is 

 possible in the cat and in the inonkey to introduce electrodes into the peri-aqucductal 

 grey or the tegmentum of the midbrain and by repetitive stimulation to evoke 

 flicio vocal responses which are identical with the normal expression of emotion by 

 these animals. These can be elicited when the brain stem is transected just ahead of 

 this region, so evidently one is not exciting an ascending pathway to some higher 

 level. After this region of the cephalic brain stem is destroyed elcctrolytically, the 

 cat no longer vocalizes in response to an adequate environmental stimulus. This 

 suggests that there is built into this part of the brain a mechanism for faciovocal 

 performance in the expression of emotions, to be differentiated from the speech- 

 mechanisms that have developed in the association cortex in the dominant hemi- 

 sphere of man. This had led me to wonder whether it would be possible, by intro- 

 ducing electrodes into the midbrain, to evoke those patterns of vocal performance 

 which you point out as being so specific for individual birds. Have experiments 

 along those lines been tried? Do you think they might be feasible; 



Thorpe. Yes, stinnilation experiments are being performed, but not so tar with 



