Boundedness of minimal degree of error (BDE) is the measure of how complex the input needs to permit an error to be detected in the language learning formalism of Wexler and Culicover . In this algorithm, the current candidate grammar will only be changed if an error is detected when the meaning of the current input is converted into a surface structure. BDE is a number that reflects the number of clauses in the most complex sentence required for learning to occur (i.e., for error detection to occur). For instance, when BDE = 2, the most complex sentence required would have no more than 2 embedded clauses.
BDE is important because it must be small enough so that a formal theory of language learning is practical. Wexler and Culicover’s original theory had a very impractical BDE of 100. They further constrained their theory to reduce BDE to 2. Some modern theories of language acquisition claim to have reduced BDE to 0.
- Wexler, K., & Culicover, P. W. (1980). Formal principles of language acquisition. Cambridge, MA: MIT Press.
(Added October 2009)