Animals, it is pointed out, learn by experience. The tiny chick that has been stung by a wasp, for instance, learns to avoid such noxious creatures for the future. This is, indeed, “learning by experience.” Obviously, however, it does not consist in an inference of a new truth from an old truth. On the contrary, it amounts to nothing more than a mere association of imagery, formed in accordance with the _law of contiguity in time_, sanctioned by the animal’s sensual appetite, and persistently conserved in its sentient memory. A bond of association is formed between the visual image of the wasp and the immediately ensuing sensation of pain. Thereafter the wasp and the pain are associated in a single complex, which the sensile memory of the animal permanently retains. We are dealing with a mere _association of contiguity_, and nothing further is required to explain the future avoidance of wasps by the chick. The abilities acquired by animals through the trial and error method are to be explained in the same way. A horse confined within an enclosure, for example, seeks egress to the fresh grass of the pasture. The fact that repeated exits through the gate of the enclosure have associated the image of its own access to the pasture with the particular spot where the gate is located induces it to approach the gate. Its quest, however, is balked by the fact that the gate is closed and latched. Thereupon, it begins to chafe under the urge of frustrated appetite. Certain actions ensue, some spontaneous and others merely reflex movements. It paws the ground, prances about, and rubs its nose against the gate. Its futile efforts to pass through the closed gate continue indefinitely and aimlessly, until, by some lucky accident, its nose happens to strike against the latch and lift it sufficiently to release the gate. This causes the gate to swing ajar, and the horse rushes out to food and freedom. By the law of contiguity, the vision of free egress through the gate is thereafter firmly associated in the horse’s sense-memory with the final sensation experienced in its nose just prior to the advent of the agreeable eventuation of its prolonged efforts. Henceforth the animal will be able to release itself from the enclosure by repeating the concatenated series of acts that memory associates with the pleasurable result. On the second occasion, however, the more remote of its futile acts will have been forgotten, and the process of opening the gate will occupy less time, though probably a certain amount of useless pawing and rubbing will still persist. Gradually, however, the number of inefficacious actions will diminish, until, after many repetitions of the experience, only those actions which directly issue in the desirable result will remain in the chain of impressions retained by memory, all others being eliminated. For, by a teleological law, making for economy of effort, all impressions not immediately and constantly connected with the gratification of