Knowledge of language and knowledge about the world: A reaction time study of invited and necessary inferences

Necessary inferences (e.g., The jury was not able to deliver its verdict by 3 o'clock. The jury did not deliver its verdict by 3 o'clock.) depend on linguistic knowledge. Invited inferences, (e.g., The jury was able to deliver its verdict by 3 o'clock. The jury delivered its verdict by 3 o'clock) depend on knowledge about the world. Responses were faster to necessary than to invited inferences when subjects verified only one of the two inference types (Experiments 1 and 3). When subjects verified both inference types there was no difference between invited and necessary inferences (Experiments 2 and 4). These data suggest that linguistic and world knowledge are psychologically distinct and that when factual knowledge is not needed in a task it is not processed. In Experiments 3 and 4 incongruent world knowledge slowed response times for both inference types. This suggests that linguistic and factual knowledge are both port of the initial representation of a sentence.