Not so simple! Mechanisms increase preference for complex explanations

Mechanisms play a central role in how we think about causality, yet not all causal explanations describe mechanisms. Across four experiments, we find that people evaluate explanations differently depending on whether or not they include mechanisms. Despite common wisdom suggesting that explanations ought to be simple (appealing to as few causes as necessary to explain an effect), the previous literature is divided over whether people adhere to this simplicity principle. Our findings suggest that the presence of mechanisms in an explanation is one factor that moderates this preference for simplicity. Without mechanisms, people typically exhibit a preference for simple explanations, consistent with probabilistic accounts. This preference is significantly reduced or even reversed when explanations contain mechanisms, suggesting that mechanisms afford a different way of evaluating explanations. Rather than focusing on probability, complex explanations that contain mechanisms may be preferred because they provide a fuller account of the underlying causal network, promoting a greater sense of understanding.