Transformational Grammar

A transformational grammar is a theory about the symbols and rules that may govern natural human languages, and are central to Chomsky's approach to language (Chomsky, 1965, 1995; Cook & Newson, 1996)  This kind of grammar involves complex, tree-like tokens called phrase markers that represent the structure of sentences.  It also involves transformational rules, where one rule would take a phrase marker as input, and would output a modified version of the phrase marker.  An example of this would be a rule that took the phrase marker for a declarative sentence as input, and output a phrase marker that represented the same sentence in the form of a question.  Transformational grammars are important in cognitive science because they represent one of the most explicit attempts to explain a complex psychological phenomenon using the approach of classical information processing.

References:

1. Chomsky, N. (1965). Aspects Of The Theory Of Syntax. Cambridge, MA: MIT Press
2. Chomsky, N. (1995). The Minimalist Program. Cambridge, MA: MIT Press.
3. Cook, V. J., & Newson, M. (1996). Chomsky's universal grammar: An introduction (Second edition). Oxford: Blackwell.