The relative difficulty of negations of conjunctions and disjunctions-a mental model perspective.

A current issue in propositional reasoning is which of negated disjunctions and conjunctions are more difficult to understand. Using the possibility generation and evaluation tasks, we investigated how people make possibility inferences from negated compound assertions such as not (A and B) and not (A or B). We derive 4 different strategies of negation from the mental model theory (the enumerative negation, the eliminative negation, the element negation, and the clause negation) to predict the relative difficulty of possibility inference from not (A and B) and not (A or B). The results of three experiments convergently demonstrate that possibility inference from not (A or B) is harder than that from not (A and B). Moreover, an interpretation of negation as the complement of the set of possibilities allowed by a compound assertion is in line with the results of not (A and B) rather than not (A or B). The overall results favor the clause negation strategy over the other strategies.