The Online Processing of Hypothetical Events.

A conditional statement If P then Q is formed by combining the two propositions P and Q together with the conditional connective If ··· then ···. When embedded under the conditional connective, the two propositions P and Q describe hypothetical events that are not actualized. It remains unclear when such hypothetical thinking is activated in the real-time comprehension of conditional statements. To tackle this problem, we conducted an eye-tracking experiment using the visual world paradigm. Participants' eye movements on the concurrent image were recorded when they were listening to the auditorily presented conditional statements. Depending on when and what critical information is added into the auditory input, there are four possible temporal slots to observe in the online processing of the conditional statement: the sentential connective If, the antecedent P, the consequent Q, and the processing of the sentence following the conditional. We mainly focused on the first three slots. First, the occurrence of the conditional connective should trigger participants to search in the visual world for the event that could not assign a truth-value to the embedded proposition. Second, if the embedded proposition P can be determined as true by an event, the hypothetical property implied by the connective would prevent the participants from excluding the consideration of other events. The consideration of other events would yield more fixations on the events where the proposition is false.