Stages of moral judgment development: Applying item response theory to Defining Issues Test data

The Defining Issues Test (DIT) has been the dominant measure of moral development. The DIT has its roots in Kohlberg’s original stage theory of moral judgment development and asks respondents to rank a set of stage typed statements in order of importance on six stories. However, the question to what extent the DIT-data match the underlying stage model was never addressed with a statistical model. Therefore, we applied item response theory (IRT) to a large data set (55,319 cases). We found that the ordering of the stages as extracted from the raw data fitted the ordering in the underlying stage model good. Furthermore, difficulty differences of stages across the stories were found and their magnitude and location were visualized. These findings are compatible with the notion of one latent moral developmental dimension and lend support to the hundreds of studies that have used the DIT-1 and by implication support the renewed DIT-2.