An Abductive Reasoning Approach to the Belief-Bias Effect

ABSTRACT. The tendency to accept or reject arguments based on own beliefs or prior knowledge rather than on the reasoning process is called the belief-bias effect. A psychological syllogistic reasoning task which has been carried out by Evans, Barston and Pollard, aims at showing this phenomenon, wherein participants were asked whether they would accept or reject a given syllogism. We discuss one specific case which is commonly assumed to be believable but not logically valid. By introducing abnormalities, abduction and background knowledge, we adequately model this case under the weak completion semantics. Our formalization reveals new questions about possible extensions in abductive reasoning. For instance, observations and their explanations might include some relevant prior abductive contextual information concerning some side-effect or leading to a contestable or rebutable side-effect. A weaker notion indicates the support of some relevant consequences by a prior abductive context. Yet another definition describes jointly supported relevant consequences, which captures the idea of two observations containing mutually supportive side-effects. Though motivated with and exemplified by the running psychology application, the various new general abductive context definitions are introduced here and given a declarative semantics for the first time, and have a much wider scope of application. Inspection points, a concept introduced by Pereira and Pinto, allows us to express these definitions syntactically and intertwine them into an operational semantics. Future work within this setting may prospect notions about contextual explanatory plausibility, of contextual model-based fault-finding, and of contextual model representation debugging.