cated movements are natural to the monkey than to the lower mammals. Berry also maintains that his experiments "have shown that voluntary imitation of a certain type does exist in white rats" and that "while this imitation is not of as high a degree as that discovered by Kinnaman in his experiments with monkeys, it is not different in kind." He thinks, also, that "a similar type of imitation exists in cats," that "cats to some extent imitate human beings" and that "cats do not instinctively kill and eat mice, but do so by imitation." He holds, however, that "instinctive imitation in cats is more important than students of animal behavior have supposed." Cole (L. W.) thinks he found evidence of voluntary imitation in the raccoon. These results, however, are open to the same objection as that raised against Hobhouse, namely, that the experiments may not have been sufficiently "controlled." In some laboratories efforts to prove the presence of voluntary imitation in the lower animals have been discontinued because of the discouraging uniformity with which negative results have been reached. No one seems to have found indisputable evidence. It is worth noting, however, that the most positive results seem to have been obtained with monkeys. What the experiments have shown unequivocally is that the animals tested learned almost exclusively by a gradual dropping off of unnecessary movements. Upon the nature of this process psychology has thus far thrown little light. Jennings says that the disturbance set up in the organism by the stimulus, by hunger or confinement, not finding an outlet by one path of discharge, seeks others in succession until one is found which relieves the disturbed condition. After repetition the change which leads to relief is reached more directly as "a result of the law of the readier resolution of physiological states after repetition." This "law" is, however, merely a statement of the fact.
It is doubtless true that intermediate stages are present between instinctive and voluntary imitation. Nevertheless, unless the work of expert observers of animal behavior during the past fifteen years is to be overthrown, the assertion may be made that man alone has developed voluntary imitation to any very important degree.
The significance of the advance to the voluntary imitation stage in development is second to none in the whole evolution of organic life for by its attainment human life, as we know it, now became possible.
It has been customary to recognize a more or less definite boundary between man and his precursors based on the development of speech by man. If, as a matter of fact, there is any value in attempting to define the boundary by a single activity, voluntary imitation may be suggested, on the objective side, at least, as of more importance than speech or language. Both voluntary imitation and speech appear to require either conceptual thought or something closely akin to it. Both may thus be taken as objective indices of the existence of that power of abstraction