The number of consecutive clicks in the train as positive or differential conditioned stimulus in dogs.

Conditioned reflexes were elaborated to trains of identical signals (clicks) of a constant number with variable interstimulus interval. The negative conditioned stimulus differed from the positive one only by the number of elements in the train. In classical defensive conditioned reflexes the latent period of motor conditioned responses to the positive stimulus was shorter than to the negative one. There were differences in the latent periods and in the speed of running to the feeding box to the positive and negative stimuli when alimentary instrumental reflexes were elaborated. The dogs ran faster to the feeding box after the positive stimuli. In 30 percent of the total number of negative stimulus presentations they did not run to the feeding box at all. There was no correlation between the reaction parameters and duration of the trains. These parameters correlate only with the number of elements in the train. Experimental data suggest that the quantitative assessment of signal trains effected in the dogs’ central nervous system, i.e. the simple count of elements may be used in its adaptive behavior.