The influence of clause order, congruency, and probability on the processing of conditionals

Abstract

Conditional information can be equally asserted in the forms if p, then q (e.g., “if I am ill, I will miss work tomorrow”) and q, if p (e.g., “I will miss work tomorrow, if I am ill”). While this type of clause order manipulation has previously been found to have no influence on the ultimate conclusions participants draw from conditional rules, we used self-paced reading to examine how it affects the real time incremental processing of everyday conditional statements. Experiment 1 revealed that clause order interacts with presuppositional congruency as readers hypothetically represent counterfactual statements. When if p, then q counterfactuals contained a presupposition that was incongruent with prior context, these statements took longer to read than when the presupposition was congruent, but for q, if p conditionals there was no such congruency effect. Experiment 2 revealed that reading times were influenced by the subjective probability of an indicative conditional regardless of clause order, with a penalty observed for low-probability statements relative to high-probability statements in both conditional clause orders. These data reveal a dissociation whereby clause order mediates the effect of suppositional congruency on reading times, but does not mediate the effect of subjective probability.

Keywords:

• Conditionals
• Clause order
• Reasoning
• Comprehension

Acknowledgments

This research was supported by a Leverhulme Trust grant (F/00 120/BT) awarded to the second author.

Notes

¹While counterfactuals contain the conditional perfect “would” in the consequent clause to indicate hypothetical possibility, indicative conditionals often have no such marker. This means that the consequent clause of a non-canonical indicative must initially be evaluated as an unqualified assertion (e.g., I will miss work tomorrow).