IRENAUS EIBL-EIBESFELDT 65 



certain movements, there is an innate ability to recognize (Lorenz, 1942). 

 Although our investigation concentrated on the motor patterns we 

 found that a certain stimuli situation must be given to release nest building, 

 retrieving and prey hunting. Ignorance oi this caused all Riess's errors. 

 Wild brown rats failed to build, not because they had less unlearned 

 responses, but because they reacted only to more specific stimuli. They 

 needed a more covered nesting site and when I offered them little tin 

 huts they started to build under this cover. 



4. THE VALUE OF THE DEPRIVATION EXPERIMENT 



Lehrmann (1953) is right in his critique, when he says that in every 

 deprivation experiment one has to answer the question: Of exactly what 

 has the animal been deprived? But we cannot follow him to his conclusion, 

 that all actual behaviour of an organism is determined by the animal's 

 experience, the only inherited basis being the bodily structures deter- 

 mining potential behaviour. He, as well as Schneirla and Hebb, insists that 

 it is practically impossible to prove that experiences during ontogeny 

 are not at work. An animal might even learn /// iifcro or in the egg. To 

 elaborate this line of thought, Schneirla (1956) and Lehrmami (1956) 

 define as experience any influence of external stimuli on development 

 and behaviour. According to this definition even biochemical changes or 

 stimuli arising from growth processes, as well as any kind of external 

 stimulation, must be termed experience. Learning is only one form of it. 



The way in which such experiences may enter development is explained 

 by Schneirla and Lehrmama on the basis of Kuo's (1932) experiment with 

 chicks. Kuo examined the ontogenesis of the food-pecking reaction in the 

 domestic fowl. These animals are able to peck for small objects immed- 

 iately after hatching, a behaviour which we would look at as innate. But 

 Kuo observed that in the three-day old embryo the neck is bent passively 

 as a result of the heartbeat, which lifts and lowers the animal's head 

 resting on the chest. At the same time the head is stimulated tactually 

 by the yolk sac, which is moved by contractions of the amnion that are 

 synchronous with the heart beat. One day later, the chick reacts to 

 external stimulation by bending its head actively, and at the same time it 

 opens and closes its beak during nodding. According to Kuo, this is due 

 to irradiation of the neural excitation caused by the nodding. At the age 

 of 8 to ID days, liquid, forced into the mouth by the head and beak move- 

 ments, is swallowed. The movements get more and more stereotyped and 

 the previously more independent head, bill and throat movements become 



