Two types of truth table task are used to examine people's mental representation of conditionals. In two within-participants experiments, participants either receive the same task-type twice (Experiment 1) or are presented successively with both a possibilities task and a truth task (Experiment 2). Experiment 3 examines how people interpret the three-option possibilities task and whether they have a clear understanding of it. The present study aims to examine, for both task-types, how participants' cognitive ability relates to the classification of the (...) truth table cases as irrelevant, and their consistency in doing so. Looking at the answer patterns, participants' cognitive ability influences their classification of the truth table cases: A positive correlation exists between cognitive ability and the number of false-antecedent cases classified as ?irrelevant?, both in the possibilities task and the truth task. This favours a suppositional representation of conditionals. (shrink)

In this study, Knauff and Johnson-Laird's visual impedance hypothesis is applied to the domain of external representations and diagrammatic reasoning. We show that the use of real objects and augmented real objects can control human interpretation and reasoning about conditionals. As participants made inferences, they also moved objects corresponding to premises. Participants who moved real objects made more invalid inferences than those who moved AR objects and those who did not manipulate objects. Our results showed that real objects impeded conditional (...) reasoning, but AR objects did not. These findings are explained by the fact that real objects may over-specify a single state that exists, while AR objects suggest multiple possibilities. (shrink)