lower animals than to man, and the farther down the series we go the less important would it become, until, among micro-organisms, we can not speak of conscious adaptation without greatly overstepping the bounds of scientific accuracy. So far as the evidence goes, learning among the lower animals is strictly a matter of association. The more intelligent of them appreciate the failure of a method quicker than the others, and the discomfort resulting from it exerts a depressant effect upon the whole neuro-muscular system which tends to break up the incipient coordinations which were involved in the original action, and even to obliterate their neural effects. All this, of course, reacts against repetition. Success, on the other hand, is attended by a pleasurable feeling, and every one has observed the joyous look of animals capable of expressing their emotions, when they have accomplished what they have been trying to do. These pleasurable feelings increase the muscular tonicity which always tends to motor discharge, and this results in a partial reinervation of the coordinated group of muscles that were involved in the original movement. This naturally deepens the existing neural effect and tends to the repetition of the movement that occasioned it.
So far as our present state of knowledge permits us to draw conclusions, the intellectual difference between man and the lower animals consists primarily in just this difference between associative reasoning on the one hand, and, on the other, inference in which the connection is obscured, by time or space, or by the complexity of the elements involved. And here, as before, the part that experience plays in determining action is the measure of intellect, only now its influence has been enormously multiplied. Articulate speech has enabled man to organize his experiences and transmit what he has learned, and it is not improbable that the higher psychical processes involved in reasoning owe to this human acquisition their development if not their origin. Speech has greatly accelerated adaptation—by no means an unimportant factor in the rapid changes of man's experience, since through it we learn from others that which may benefit or injure, and so avoid what might mean destruction of the species. And then, too, by enlarging the sum of the experiences it has greatly increased the facility in acquisition and assimilation which plays so important a role in human progress.
Learning in man, whether it be a new adaptation to a changed situation or the acceptance of an intellectual truth or moral principle, depends much upon the content of the individual mind, and this assumes infinitely greater importance in man than in the lower animals because of the immense complication of his environment. With animals this content embraces at most relation to the physical world and to other animals, but with man the physical world means and