Syllogistic Reasoning with Generic Premises: The Generic Overgeneralization Effect

Generics are statements that are not explicitly quantified and that express generalizations, such as ‘ducks lay eggs’. Intuitively, the generic (non-quantified) form of such statements seems to be true. Furthermore, people seem to be prone to an interesting error: treating the universal form of characteristic generic assertions (e.g., ‘all ducks lay eggs’) as true, even though they are, upon a moment’s reflection, patently false. How would people interpret generic assertions when they are used as premises in a syllogistic reasoning task? Although the normative strategy to optimize production of valid conclusions would be to treat generics as existential assertions, people displayed a strong tendency to assimilate generics to universal assertions. As in prior comprehension studies, generics behave as the prototypical default form for expressing generalizations about the world.