There is a way, of course, to ask which changes are universal, whether there is a generalized developmental function, and whether individual differences represent simple variability or meaningful alternative developmental pathways. This is to follow a sample of individuals as they grow older. Although most would agree that such longitudinal studies provide the ideal methodology for studying change and developmental pathways, they are the exception rather than the rule. There are many reasons for this, mostly logistic and pragmatic: Following the same individuals over long time periods requires extensive resources; designing measures that remain valid across different ages is difficult; and maintaining interest and commitment to a single project over the span required by longitudinal work is chancy for both researchers and subjects.
The study I will describe is the Munich Longitudinal Study on the Genesis of Individual Competencies (LOGIC). It was funded by the Max Planck Society and was directed by Prof. Dr. Franz E. Weinert, a Director of the Max Planck Institute for Psychological Research, in Munich. The participants included about 200 children who were 4 years old at the beginning of the study, and 13 years old at the end. Data collection was intensive. Information from about 6 hours of testing was available for each child for each of the 9 years of the study,and about 60% of the children were seen several times a year in their schools in a companion school study.
The focus of the study was on individual differences in developmental pathways across a variety of cognitive, social, and personality areas. It is impossible to convey a complete picture of the broad scope or results of this study, which was the collective effort of a dozen researchers (of which I was one) and more than 20 research assistants. Rather, I will highlight examples (and responsible researchers) of how data from this multifaceted, longitudinal design contribute to a richer empirical and theoretical understanding of development.
Age-group comparisons replicated findings in the literature. Mean memory strategy use increased linearly with age, as did mean strategy effectiveness. However, this gradual acquisition was not shown at the individual level. Indeed, the researchers reported that 'the group data on strategy acquisition that have been reported in cross-sectional studies massively obscure the individual developmental paths.' Individual differences were not simply differences in rate. Although children discovered strategies at different times, development, once a strategy was discovered, was far from uniform. In fact, there were more discontinuities (strategy discovery, loss, then subsequent rediscovery, leaps, and drops) than continuities (only 8% showed gradual increases). Of course, such discontinuities are only interesting to the extent that they predict something about later developmental outcomes. There was some suggestion that children who used strategies and understood their function were more likely to maintain them than children who used them mindlessly. This provided partial support for the hypothesis that strategy acquisition per se is not related to recall performance unless mediated by conceptual understanding of the function of deliberate strategic behaviors. The longitudinal data also pinpointed the essential transition point when strategy development became related to performance development (around 8 years), suggesting the period where subsequent, more experimental studies should focus.
A comparison of different pathways in the growth of moral motivation showed that the level of motivation (low, medium, high) at younger ages (6-7 years) did not predict moral motivation at ages 8-11. Motivation at ages 8-9 predicted motivation later only for those children who were very low or high. In addition, although all children justified moral rules in terms of both moral strictures and empathic concerns, an eary preference for moral strictures predicted stronger later moral motivation. The role of variable pathways in the development of moral motivation and the relation of moral motivation to behavior provide new directions for research, theory, and ethical training.
Shyness with strangers (ascribed to fear of the unfamiliar) was stable over time; shyness in the classroom (ascribed to fear of peer rejection) was not stable over time; and a moderate consistency between shyness with strangers and shyness in the classroom decreased with increasing group familiarity. These patterns, replicated across preschool and school contexts, were hypothesized to be examples of a much more general scheme: 'Shyness with strangers is a special instance of a relationship-unspecific trait, and shyness due to social-evaluative concerns is a special instance of a relationship-specific individual attribute.' Because the LOGIC sample was sufficiently large, it was possible to test some of the implications of this model. For example, extreme group analyses showed that peer rejection seemed to lead to shyness in familiar settings and that shyness in familiar settings (but not stranger shyness) was related to lower later social self-esteem.
The project leaders over the years of the study included Drs. Jens Asendorpf, Merry Bullock, Andreas Helmke, Monika Knopf, Julius Kuhl, Gertrud Nunner-Winkler, Wolfgang Schneider, Elsbeth Stern, Gerhard Strube, Angelika Weber, along with the following collaborators: Drs. Marcel van Aken, Marcus Hasselhorn, Christina Muekusch, Jan Naeslund, Josef Perner, Beate Sodian, Michael Waldmann, Heinz Wimmer, Albert Ziegler.