A central research paradigm in cognitive science consists of the collection of protocols of subjects thinking aloud as they solve problems, the construction of computational models of the problem-solving process, and control experimentation designed to test predictions derived from the models. This research paradigm is deployed by Rips ( 1989) in a lucid study of deductive inference processes. In this section, Rips' ( 1989) research will be described, and, then, a general commentary will be presented.
Rips' ( 1989) research concerns reasoning with knight-knave problems.
Knight-knave puzzles begin like this: Suppose there is an island where there are just two sorts of inhabitants -- knights who always tell the truth and knaves who always lie. Nothing distinguishes knights and knaves but their lying or truth-telling propensity. You overhear a conversation between two or more inhabitants, and on the basis of their conversation, you must decide which of the individuals are knights and which are knaves. Smullyan ( 1978) is a rich source of these puzzles, of which the following is an example: