4 
CURT P. RICHTER 
be directed toward the spontaneous activities of humans and 
animals. 
The present work was carried on in the Psychological Labora¬ 
tory of the Johns Hopkins University under the direction of Dr. 
John B. Watson. I am deeply indebted to Dr. Watson for his 
help and encouragement and for the complete freedom allowed 
me in carrying on my work. The inspiration to this work came to 
a very great extent from the numerous suggestive experiments of 
Cannon and Carlson on the Hunger Problem. It came also from 
the Behavior work of Jennings on the Lower Organisms and from 
the many stimulating experiments of Szymanski on Activity 
Problems. I am very much indebted to all of these workers. I 
am indebted for help and criticism to Dr. Edwin B. Holt, Dr. 
Knight Dunlap, Dr. H. H. Donaldson, and Dr. E. Sanford. I am 
also indebted to my friends Mr. Ging Wang and Mr. David 
Brunswick for many helpful suggestions and assistance. 
I. PERIODIC NATURE OF SPONTANEOUS ACTIVITY 
For carrying out the purposes of the following experiments two 
things were required: (1) A situation as free as possible from all 
active external stimulation, and (2) an arrangement for recording 
the activity of animals over long periods of time without in any 
way stimulating the animals themselves. 
The conditions of the first requirement were met in the following 
way. Noises were eliminated by carrying on the experiments in 
a room fitted with large double sound-proof doors and very 
thick sound-proof walls. All avoidable odours were taken care 
of by a very good ventilation system. The air was always 
fresh and free from the usual odors found in animal laboratories. 
The room was made completely impervious to light rays from 
the outside by placing heavy covering of cloth and many layers 
of thick opaque paper over the window. Because of the double 
doors and thick wall the room was also almost completely im¬ 
pervious to temperature changes from the outside. It was 
possible to maintain the temperature at one constant level for 
weeks at a time. The conditions of the second requirement were 
