The proposed study seeks to explain the linkages between education, modernization, modernity, and fertility through a two-stage empirical study of determinants of demographic attitudes and behavior. The model will be tested by means of a longitudinal investigation of attitudes, intentions, and behavior among a sample of 5,200 males and females aged 11-17 in metropolitan and provincial cantons of Costa Rica. Self-administered questionnaires will be distributed to 4,800 sixth, eighth, ninth, and eleventh graders and to 400 adolescent women not attending school. In-depth qualitative data will be otained through individual and group interviews with sub-samples of this population. Data collection in 1984 will be repeated with the same respondents in 1986, whether or not they are still in school. Dependent variables include level and change in knowledge, attitudes, preferences, intentions, and behavior with respect to a number of fertility related topics, including age at marriage, age at first birth, and completed family size. Independent variables are modernization (measured by county level aggregate socio-demographic characteristics) and degree of schooling. The principal intervening variable is psychological modernity, including perceived norms, aspirations, and such personality characteristics as personal efficacy, time sense, cognitive coping, and mass media perceptions. Collaborating centers have had previous successful experience with a joint research project. A major hypothesis holds that mass media related information and aspirations constitute critical components of modernity that mediate between education and the fertility variables. The study should be of importance both for the theory of demographic transition and for those LDCs where stalled birth rates may require the stimulation of public demand. It should aid U.S. policy-makers both in assessing the broad impact of future educational trends on fertility in LDCs, and in providing scientifically based guidelines for technical assistance to countries desiring to accelerate fertility declines through educational programming.