In the later period of childhood, acquired interests begin to be formed and, coincident with this, active attention appears. The child begins to be interested in the product, not merely in the process. The mind at this period is most retentive of sense impressions. This is consequently the time to bring the child into immediate contact with his environment through his senses, in such departments as nature study and field work in geography. Thus is laid the basis of future potentialities of imagery, and through it appreciation of literature. On account of the acuteness of sense activity at this period, this is also the time for memorization of fine passages of prose and poetry. The child's thinking is still of the pictorial rather than of the abstract order, though the powers of generalization and language are considerably extended. The social interests are not yet strong, and hence co-operation for a common purpose is largely absent. His games show a tendency toward individualism. When co-operative games are indulged in, he is usually willing to sacrifice the interests of his team to his own personal glorification. 3. ADOLESCENCE =A. Physical Characteristics.=--In early adolescence the characteristic physical accompaniments of early childhood are repeated, namely, rapid growth and lack of muscular co-ordination. From twelve to fifteen, girls grow more rapidly than boys and are actually taller and heavier than boys at corresponding ages. From fifteen onward, however, the boys rapidly outstrip the girls in growth. Lack of muscular co-ordination is responsible for the awkward movements, ungainly appearance, ungraceful carriage, with their attendant self-consciousness, so characteristic of both boys and girls in early adolescence. =B. Mental Characteristics.=--Ideas are gradually freed from their sensory accompaniments. The child thinks in symbols rather than in sensory images. Consequently there is a greater power of abstraction and reflective thought. This is therefore the period for emphasizing those subjects requiring logical reasoning, for example, mathematics, science, and the reflective aspects of grammar, history, and geography.