The psychological literature on stages of cognitive development was reviewed and found to contain support for the idea that stages represent ordinal, qualitative changes in organized knowledge structures. There was a lack of empirical support for the notions that stage transitions are abrupt and concurrent. All of these findings were found to be consistent with new connectionist models of cognitive development. A fundamental insight emerged from working with such models, namely, that stages result when a network solves part of a problem before solving all of the problem. Partial problem solving in connectionist networks is likely to occur under the following conditions: hidden unit herding, over-generalization, training pattern bias, and hidden unit recruitment.
Thomas R. Shultz