Current theories of human deductive reasoning make different claims about the representation of logical statements in memory. Syntactically-based theories claim that abstract logical forms are represented veridically in memory, separate from content, whereas semantic theories propose that naive reasoners represent combinations of possibilities that are based on the content of statements. We tested these predictions in two experiments in which participants had to recall and recognize statements of different logical forms. Results indicate that memory for logical form is not veridical, thus failing to support the syntactic view. In particular, results suggest that naive participants tend, whenever possible, to represent only a single possibility for a statement of any logical form. These findings are consistent with semantic theories of human deductive reasoning and have significant implications for all theories of reasoning.

How do people deal with ambiguity and indeterminacy of incoming information? The results of the two reported experiments indicate that both young children and adults tend to reduce ambiguity, systematically 'converting' noninformative propositions into more informative ones. Although young children and older participants use different strategies, high rates of conversions were found in both groups. These conversions seem to represent an adaptive cognitive constraint — a tendency to reduce ambiguity and to increase the informativeness of incoming information.