A single process for deductive and inductive inference? Examining the impact of conclusion typicality and argument validity on immediate inferences

Inductive and deductive inferences have been assumed to rely on two qualitatively distinct processes by dual-process theories. However, studies examining the predictions of this theory have yielded mixed results, with several studies showing that a single process underlies both deductive and inductive judgments. Previous studies have used a range of manipulations, response options, and analytical techniques, which might partly explain the inconclusive findings. In this study, we conducted five experiments (overall N = 614) manipulating the typicality of the category-member relationship (typical vs. atypical pairs) and the quantifier of premises (all/universal vs. most/particular) in reasoning arguments. Dual-process theories predict a double-dissociation pattern in which the quantifier manipulation would impact deductive judgments more than inductive judgments, while typicality would have the reverse effect. To test these predictions, we employed a range of experimental tasks (within- and between-subject), response formats (binary and Likert), and analytical techniques (Bayesian hierarchical regression and state-trace analysis). The results failed to support the dual-process theory in that the predicted double-dissociation effect was not observed in most of the experiments. These findings align with a single-process framework, as proposed by the new paradigm of reasoning, for both deductive and inductive inferences. The implications of these findings for both dual- and single-process accounts are discussed.