HUMAN REASONING - DEDUCTION RULES OR MENTAL MODELS, OR BOTH

A good deal of energy is currently being expended into discovering the fundamental machinery underlying deductive reasoning. Is it based upo n mental models (arrays) or deduction rules (propositions)? The appeal of finding a ''grand unified theory'' of reasoning is obvious, but th e likelihood of achieving this must also be considered. This paper dis cusses the use of experimental psychology in attempts to discover the processes associated with the fundamental reasoning mechanism. One par ticular problem is that individuals can use different strategies to so lve reasoning problems. The consequences of this are assessed in relat ion to'' (1) the assumptions underlying the experiments, (2) the choic e of tasks and task presentations intended to enable the fundamental r easoning processes to be viewed directly, and (3) the power status of the theories and the nature of the evidence required to show that eith er theory is superior. Under close scrutiny the debate appears to be u nresolvable by using empirical techniques. However, although the main conclusions are negative, it is suggested that approaches that directl y investigate individual differences are likely to be useful alternati ves.