Date on Master's Thesis/Doctoral Dissertation


Document Type

Master's Thesis

Degree Name





Animal behavior--Endocrine aspects


It is not the primary purpose of this present work to treat the problem of the evolution of behavior, but rather to give an analysis of animal behavior as observed. These observations may appear as simple tests, but they make possible a new way to measure the capacity and determine the rate of learning by the animal mind. Progress in learning takes place through increased variety and precision of the movements brought about by stimulation and is very clearly observed in Amoeba, where we find the production of varied movements and the resolution of one physiological state into another. Thus the organism reacts no longer by trial, - by the overproduction of movements, - but by a single fixed response, appropriate to the occasion. We often speak of these responses as reflexes, tropisms, habits, and instincts. These fixed responses can be firmly established and they will not give way until a long period intervenes and the old responses are modified or destroyed by a new environment. Observation and experiment show that many variations exist in the behavior of animals. It is known that organisms have developed special types of behavior, such as burrowing or running along the bottom of a pond. When a response has been established by many repetitions, the organism will lose all tendency to react in any other way than to the particular one in question. In the early period, during which the organism is establishing such a response, it will retain the power of attempting other methods of reaction, such as performing other movements. But these movements will be ineffectual, because the structures of the organism may not be best adapted to their performance. They will not relieve the organism from stimulation, hence they will be quickly exchanged for those movements which are effective. Then the organism will react always by those movements on which its structure is based. If these ineffectual movements are not observed, it will appear that the organism has been rigidly limited from the beginning to this one type of behavior. There is the view that animal behavior is based largely on this selection from among varied movements and that there is a kind of retention of the selected movements.