Longitudinal studies of mental development.

Two longitudinal research projects--Individual Statistics and Evaluation through Follow-up of Students (UGU)--are presented. Their overriding aim is evaluation of the role of school in individual developmental processes. Mental development is one interest of study. The sequential design and data collected are briefly presented. Four representative samples of students born 1948, 1953, 1967 and 1972 are under study. Two smaller exemplifying studies are presented. The first is a cross-sectional comparison between thirteen-year-olds tested in 1961, 1966 and 1980 with identical tests. The average level of results on spatial and reasoning tests have risen since 1961. There were no changes in differences between students from white-collar and blue-collar background. Differences between boys and girls had changed, though. There was no verbal test difference in 1961 but in 1980 girls performed better than boys. Concerning spatial and reasoning ability, boys were clearly better 1961 but that difference had practically disappeared 1980. In the other study MMR students are defined within the 1967-born cohort. Some data on their school-experiences are presented. They face more difficulties and have more remedial teaching than other low ability students, but most of them complete compulsory schooling and 2/3 have plans for secondary education. Plans for future analyses are presented.