that which serves as food. In other words the animal responds primarily to water undulations, regardless of their cause, because it is through such undulations that it receives notice of the presence of food. In its most typical form instinct is thus seen to be chiefly a matter of animal organization, and the response to stimuli to be largely mechanical. This makes stable conditions necessary if it is to meet educational needs. But even here there is a little variation in the manner of reaction. Necturus has learned to discriminate somewhat between experiences, for, according to Whitman, "there is unmistakably a power of inhibition strong enough to counteract the strongest motive to act—the hunger of a starving animal in the presence of food." But such limited power of reaction does not go far, and it will meet the needs of animals only so long as their life is of the simplest sort. They are probably capable of few adaptations, and these must be made at an enormous cost of time and life. But as life becomes more complex and less regular these instinctive responses do not answer. Animals must now learn to remember, and their actions must be guided by past experiences of threatening disaster, else they can not survive in the struggle.
Not many experiments have been made on the educability of animals low in the scale, but fishes have been taught to refrain from attacking minnows that are their usual food, by separating them with a glass partition extending across the aquarium until the larger fishes learn by repeated bumps on the nose that the little ones are not to be eaten. Thorndike has shown also that the minnow, Fundulus, can learn to find its way through a series of three partitions, each with an opening so located as to make the journey circuitous, and that it gradually improves on its previous record by eliminating blunders until finally it learns to go directly to each opening. While we do not know much about the mental processes here, it grows increasingly harder to explain action solely by the neural mechanism. Experience is evidently taking a more active part in the animal's life. The nervous system is becoming more flexible, more adaptable.
Recent observation has somewhat modified our views regarding action among lower animals. Jennings's studies indicate that the method of trial and error is common even in one-celled organisms. This method, wherever found, unquestionably involves in some degree the utilization of experience. Such creatures can no longer be considered as merely reflex organisms in the presence of new needs and
- Loc. cit., p. 305.
- See statement of Moebius's experiment in Darwin's "Descent of Man," second edition, p. 76, and Triplett's "The Educability of the Perch," Am. Journal of Psychology, Vol. 12, p. 354.
- Am. Naturalist, Vol. 33, p. 923.
- "Contributions to the Study of the Behavior of Lower Organisms," p. 237; Carnegie Institution, Washington, 1904. "Behavior of Lower Organisms," 1906.