156 THE SOCIAL LIFE OF ANIMALS 



bird to slow down rather than for the slower bird 

 to speed up. The paired birds tended to take the 

 same time and to make the same errors. Given suf- 

 ficient training, they might make perfect scores so 



Trials 



Fig. 29. Parrakeets learn equally well if trained when 

 isolated, whether they are caged singly or in pairs. A, 

 time per trial; B, errors per trial. 



