We now take up playful apperception of new impressions. The deep-rooted impulse to bring everything within the sphere of our own powers is especially powerful in the presence of novelty, of what is unfamiliar. We experience an almost irresistible desire to examine closely any strange object and make ourselves acquainted with its properties. Curiosity is the name given to the playful manifestation of attention which results from this tendency. Since I introduced it among the plays in my work on animals I have been told that curiosity is no play; but if we keep to our principle that the exercise of an impulse merely for the sake of the pleasure we derive from it is to be called play, then I am unable to see why curiosity should form an exception. It stands midway between two kinds of perception as applied to what is new, but is identical with neither. On one side is the impulse to inquire into the practical use of the unfamiliar object, whether it is beneficial or injurious; on the other side is thirst for knowledge, not entirely with a view to appropriation, but more concerned with placing the object properly in our system of things known. But curiosity, while it does depend on the stimulus[323] of novelty, concerns itself primarily neither with the practical value of the thing nor with its theoretic significance. It simply enjoys the agreeable emotional effects which arise when a new concept does not readily adjust itself to the beaten track of the habitual, and requires paths at least partially new to be opened before it. The interest attaching to scientific investigation is logical and formal, but that excited by curiosity may be said to be material. The freshness of the untried belongs to this new mental heritage, and is as exhilarating as the mountain climber’s discovery of a new path to some coveted summit. Where such pleasure becomes the ground of activity, that activity is play. For illustrative purposes let us suppose a landslide. Practical interest would at once apply to the proper authorities to find out the extent of damage caused by the catastrophe; scientific and learned curiosity would investigate the causes; while the simply curious would run from all directions just to see what was happening, using their powers of attention playfully.