Logical intuitions and heuristic reflections : rethinking the role of intuition in probability judgements

This thesis aims to further our understanding of the role that intuition plays in human reasoning when making probability judgements. It attempts to: a) gain a better understanding of the cognitive processes underlying these judgements, b) determine how individual differences impacts the logicality of these judgements, and c) test original and theoretically-driven ways to increase logical intuitions in probability judgements. Classically, it is assumed that people make biased judgements because they rely on an intuitive thinking system (System 1) and apply the representativeness heuristic to make conjunctive probability judgements. In contrast, logical judgements are assumed to arise from the use of deliberation (System 2) to overrule the prepotent heuristic response and replace it with a logical one. Recent research; however, has challenged this claim and instead proposes that our intuitions do not always lead us astray. In fact, they can reflect a sensitivity to logic that is implicit, and potentially happens automatically and outside of awareness. This thesis takes this notion one step further and asks whether it is the slower, more deliberative, thinking system which may be vulnerable to prior beliefs and biases. A series of five experiments examined the relative impact of heuristic and logical considerations on probability judgements. The results indicated that people are readily able to detect the conflict underlying intuitive and deliberative assessments, and that people effortlessly engage in deliberative processing, which suggests they are not simply cognitive misers who fail to reason in line with the principles of logic because they either lack the cognitive ability or the motivation to do so. The results also supported the idea that people can intuit logical judgements (i.e., judgements in accordance with the laws of probability) when they rely on System 1 thinking; however, when they deliberate or use System 2 thinking, that is when the heuristic biases their judgements