sensitive to the rights and feelings of others. At the same time they express more doubts about their ability to know exactly what to do in any given situation in which they are likely to be involved.
The data from the Purdue Opinion Poll are consistent with the results of studies carried out by Kuhn and others ( 1977). Kuhn and her co-researchers asked 265 subjects between the ages of ten and fifty to solve three Piagetian problems designed to assess the attainment of the formal operations stage of cognitive development and also asked them to answer questions from Kohlberg ( 1963b) moral judgment interview schedule. An analysis of the respondents' replies indicated that reasoning ability, as indicated by the attainment of formal operations, is fundamental to and parallels the development of highly principled moral judgment (Level III in Table 15:2).
Although adolescence is the period separating childhood from adulthood, it is easier to say what adolescents are not than what they are. It is relatively easy to determine where adolescence begins, but where it ends varies greatly among cultures, social classes, and individuals. There is a tendency for our society to prolong adolescence. This has the effect of protecting young people against exploitation and society against inept workers, but it also makes adolescents outsiders in an adult world.
The physical aspects of adolescence involve sexual development, as well as increases in height and weight. At puberty, adolescents also take on the secondary sex characteristics of adults. Girls tend to mature about two years earlier than boys. Although girls and boys are fairly equal in strength and skill during childhood, boys reaching puberty begin to excel in large-muscle activities. Girls maintain their skill in some motor activities, especially those involving control and accuracy, but actually become less competent in others. Sex differences in physical development are causal factors in this loss of skill, but motivation may be involved as well.
For many years there has been a tendency for children to grow up to be taller than their parents. This secular trend, as it is termed, has been going on at least since 1840 in Northern European countries, and in the United States for almost a hundred years. Recent evidence suggests that the trend in the United States may have come to a halt in the mid-1950s. The increases in height may have resulted from improved nutrition, but freedom from extreme stress and cross-matings among different ethnic groups have also been suggested as causes. Increases in weight to an average of 105 pounds appear to trigger the menarche in women. Better-educated (and presumably better-nourished) women tend to