that to do so for tests of imitation would be as difficult as well as more necessary.
Birds would therefore appear to be very good subjects for a study of imitation since at least the higher ones have the olfactory lobes really very little developed and they probably use the sense of smell to small extent. For them the sense of sight is predominant as it is in man. In fact a good argument might be made to show that it plays even a larger role with birds than with almost any other animal. Edinger's work has shown how the keenness of vision, the large eye and the optic lobes enable them to see acutely and from afar. It is clear, then, that a careful estimate of the sort of contribution made by the separate sense fields is a prerequisite of the study of imitation. But what advantage is there in an animal which uses more exclusively the eye than the sense of smell as the source of stimuli which guide it to action? Obviously if our experimental apparatus were devised to appeal to the sense of smell, and if we as observers could detect that the animal, instead of acting on the odor stimulus, responded rather to the model set by another, then the odor guided animal w r ould be the equal of those in which sight is predominant.
It is probable, however, that the eye requires in a less rigid way the following instinct. Certainly the criterion of the presence of imitation almost universally used by students of imitation, both human and animal, has shown that what the imitating animal sees done is thought to be all important. It is commonly stated that such an animal seemed to see what the animal to be imitated was doing. Seeing this, it did not work with the apparatus as it had previously done, but changed its method and followed the copy. Certainly such a standard as the above requires that the animal use the sense of sight and the more certain we are that keenness of vision is possessed by the animal the better prepared are we to start with.
Very few species of birds exist that are not the natural prey either of their own kind or other animals. To escape their enemies or to capture their prey very sudden and rapid action is absolutely necessary. The sensing of stimuli from afar and quick response is one of the most striking characteristics of birds. Can one bird imitate another and thus obtain food and escape enemies? If so, then we have in a way what may be called "vicarious functioning" to which, in fact, all imitation is equivalent. True we may find in birds no higher kind of imitation than tins, following instinct. Bird migrations and their other sorts of gregariousness in addition to the demand for sudden response mentioned above all these emphasize the value to them of instinctive imitation. Illustrations of this
