BEHAVIORISTIC STUDY OF THE RAT 
7 
the recurrence of the periods probably for the reason that he 
made no attempt to keep the conditions of the experiment 
constant over longer periods of time. He did his work in an 
ordinary room subject to the daily changes of temperature and 
illumination due to the day and night on the outside. 
For the reason that the rat shows a number of periods during 
the twenty-four hours Szymanski speaks of it as a polyphasic 
animal in contrast to the monophasic animals, like the human 
adult for instance, which show only one long period of activity 
and one period of inactivity during the twenty-four hours. That 
this classification is of somewhat doubtful value, and that it 
describes their reactions to external stimuli rather than the func¬ 
tion of any mechanism inherent in the organism itself may be 
brought out by the consideration of some experiments on the 
Fig. 3. Record of Spontaneous Activity of Ten Months Human Infant 
During Uninterrupted Sleep 
Time in hours. From work of Miss Tomi Wada 
human infant and adults carried out in the Phipps Clinic Psycho¬ 
logical Laboratory during the past year by Miss Tomi Wada of 
Columbia University (11). 
Miss Wada was able to confirm on humans what was found in 
the experiments on rats. She used the same technique that was 
employed in the rat work. In the human infant she found that the 
same regularity of the alternation of the periods of activity and 
inactivity prevails. She obtained her records chiefly during the 
long period of sleep at night. The frequent interruptions for 
feeding and bathing etc. make it difficult to obtain records of 
activity during the day. A typical curve of the activity of a ten 
months infant during sleep is shown in figure 3. These periods 
come at the rate of one every fifty to fifty-five minutes. The 
regularity of these periods is very striking. Miss Wada found 
further that the activity of the human adult during sleep is also 
