Developmental Systems Group
In This Section:
The Developmental Systems Group (DSG) began in 2005 within the Department of Human Development and Family Studies (HDFS) at the Pennsylvania State University. We aim to stimulate, coordinate, support, and disseminate research and teaching about systems thinking in the study of development, particularly in developmental science. Although systems thinking has a long history within HDFS, we have only recently begun to adapt advanced statistical techniques, such as dynamic modeling, from the fields of mathematical systems theory and engineering for use in developmental science. These techniques are necessary for analyzing non-ergodic processes—processes wherein specific individuals do not follow the same process as the so-called “average” person (see “Ergodicity Explained” for a more detailed explanation). Because most developmental processes are non-ergodic, we propose that most developmental research designs and analyses need to be conducted at the level of the individual, which is frequently called Person-Based Design and Data Analysis or Person-Specific Data Analysis..
The DSG action program contains four components
- Scientific Development
- Computational Development
- Educational Development
- Strategic Development
Scientific Development
Person-based designs and modeling in psychology are currently marginal, even though they are necessary when considering non-ergodic processes. Therefore, we need a major reorganization at the levels of scientific modeling, hypothesis testing, and applications. We must specifically emphasize how to integrate current inter-individual approaches with new person-based approaches. Modeling techniques, such as time series and signal analyses, that have been developed in the physical sciences and econometrics need to adapted to the social sciences, and new modeling techniques have to be developed to meet the special needs of psychological research with respect to systems of individual development, families, and prevention and intervention.
Computational Development
Commercial statistical software programs now available hardly have suitable facilities to meet the requirements for multivariate psychological time series analysis and systems modeling. Within the DSG, new software is being developed but needs to be customized and made accessible for general use.
Educational Development
There are not yet any structured courses nor suitable textbooks on person-based methodology and data analysis for psychology students in general, and HDFS and other College of Health and Human Development students in particular. Within the DSG, we are setting up a video network for on-line dissemination of courses in person-based data analysis and methodology. We are also developing texts and other course materials.
Strategic Development
Apart from the participants within HDFS, several other research groups within the U.S. and in Europe participate in the DSG. New platforms have to be created within the major organizations of psychological research to support research in the new person-based paradigm. Also, collaborations with the medical and engineering sciences will open up new possibilities for multi-disciplinary research. The DSG will actively pursue the action program sketched above. We have begun with a series of symposia using external financial support (e.g., APA, NIH) and through the submission of specific research project proposals (NSF, ADA, NIH).
Ergodicity
For a more detailed explanation of ergodic processes and applied examples, please see Molenaar’s (in press) 
The non-equivalence of structures of inter- and intra-individual variation associated with non-ergodic psychological processes.