A technique for the analysis of ecosystems developed by Odum focuses on the nature of interactions which take place within the system being considered. This technique can be used to assess the contribution of any variable to an interaction. Using data derived from previous research conducted by Feather, the authors employ this technique to examine the way in which probability estimates and actual achievement interact as a system. Specifically, the data were studied to determine how achievement and probability of success varied over time for each treatment group. The interactions were incorporated into a model allowing symbolic representation to be translated into a useable mathematical form. Thus each dynamic variable in the system can be represented by a differential equation which, when combined, provide data on the changes of each variable over time. (AJL)