=When to Develop Interests.=--It is to be noted further concerning many of these forms of interest, that youth is the special period for their development. The child who does not, during his early years, have an opportunity to develop his social tendencies, is not likely later in life to acquire an interest in his fellow-men. In the same manner, if youth is spent in surroundings void of aesthetic elements, manhood will be lacking in artistic interests. It is in youth also that our intellectual interests, such as love of reading, of the study of nature, of mathematics, must be laid. =Interests Must be Limited.=--While emphasizing the importance of establishing a wide range of interests when educating a child, the teacher must remember that there is danger in a child acquiring too wide a range. This can result only in a dissipation of effort over many fields. While this prevents narrowness of vision and gives versatility of disposition, it may prevent the attainment of efficiency in any department, and make of the youth the proverbial "Jack-of-all-trades." A study of the feeling of interest has been made at this stage on account of its close connection with the problem of attention, and in fact with the whole learning process. An examination of the other classes of feeling will be made at a later stage in the course. CHAPTER XXV SENSE PERCEPTION =Sensation and Perception Distinguished.=--Sensation and perception are two terms applied usually without much distinction of meaning to our recognition of the world of objects. When, for instance, a man draws near to a stove, he may say that it gives him a _sensation_ of heat, or perhaps that he _perceives_ it to be hot. In psychology, however, the term sensation has been used in two somewhat different meanings. By some the term is used to signify a state of consciousness conditioned merely upon the stimulation of a sense organ, as the eye, ear, etc., by its appropriate stimulus. To others, however, sensation signifies rather a mental image experienced by the mind as it reacts upon and interprets any sensory impression. Perception, on the other hand, signifies the recognition of an external object as presented to the mind here and now.