568 W. T. JAMES 



the same as for the others of group B-minus. As we shall 

 point out later, however, this animal varied from the others of 

 the group when trained with the motor response, thus plac- 

 ing her in the mixed group instead of the pure B-minus group. 

 Her reactions in the salivary performance conformed to the 

 group, but that does not mean that all other performances 

 will conform. The significance of this will become clear when 

 we discuss pure and mixed behavioral types. 



Summary. The dogs of the intermediate groups A-plus 

 and B-minus approach the behavior of the polar groups A 

 and B, but do not reach the extremes. Those of the A-plus 

 type are quiet, but never become completely indifferent to 

 the laboratory as do the animals of the A group. They re- 

 main alert and subject to stimulation over a long period of 

 time. Some have difficulty in developing a stable negative 

 response. A strong reaction to new and strange stimuli is 

 given, but the animals are not greatly disturbed. Most of 

 them are able to make adjustments to the signal for the 

 motor reaction and the signal for food in the same experi- 

 mental session. Although alert and active, the dogs of the 

 B-minus group differ from those of the polar group in that 

 they are better able to restrain themselves and form differ- 

 entiation reactions, which are too confusing for the more 

 excitable dogs of group B. They are slightly disturbed by 

 the introduction of the motor reaction, since the food taking 

 response becomes inhibited. They form good avoiding reac- 

 tions, however, and are capable of differentiating between 

 signals by this method. 



In general, the animals of the intermediate types are more 

 stable and better balanced than either of the polar types. 



DISCUSSION 



In the experiment just described, thirty-six dogs were ob- 

 served as the adjustment to food taking under controlled 

 conditions was made. The external factors, the stimuli, re- 

 mained constant, but many variations in behavior among the 

 dogs occurred in the course of the performance. These modi- 



