Foundations Of Cognitive Science

Graceful Degradation

In a symbolic system removing part of the system will result in a clear degradation of performance. Removing a symbol token will result in the loss of the information stored in that token. The loss of an operating procedure destroys the systems ability to perform the missing process. The fall in performance is sudden and clearly defined. In a connectionist system performance does fall sharply with either damage to the system or erroneous inputs. Instead, the performance will decline gradually, depending on the nature of the loss and the architecture of the system. This property means that connectionist models still function relatively error free when the system has damage to its connections or units or when the input stimuli is incomplete.


  1. Bechtel, W., & Abrahamsen, A. (1991). Connectionism and the mind: An introduction to parallel processing in networks. Cambridge, MA: Blackwell