The various sensations which the baby experiences—heat, light, contact, motion, etc.—are so many stimuli to the development of these centers. If the stimulus is too great, the development is sometimes unduly hastened, with serious results, which show themselves chiefly in later life. The child who is brought up a noisy room, is constantly talked to and fondled, is likely to develop prematurely, to talk and walk at an early age; also to fall into nervous decay at an early age. And even if by reason of an unusually good heredity he escapes these dangers, it is almost certain that his intellectual power is not so great in adult life as it would have been under more favorable conditions. A new baby, like a young plant, requires darkness and quiet for the most part. As he grows older, and shows a spontaneous interest in his surroundings, he may fittingly have more light, more companionship, and experience more sensations.