Research has documented two effects of interfeature causal knowledge on classification. A causal status effect occurs when features that are causes are more important to category membership than their effects. A coherence effect occurs when combinations of features that are consistent with causal laws provide additional evidence of category membership. In this study, we found that stronger causal relations led to a weaker causal status effect and a stronger coherence effect (Experiment 1), that weaker alternative causes led to stronger causal status and coherence effects (Experiment 2), and that "essentialized" categories led to a stronger causal status effect (Experiment 3), albeit only for probabilistic causal links (Experiment 4). In addition, the causal status effect was mediated by features' subjective category validity, the probability they occur in category members. These findings were consistent with a generative model of categorization but inconsistent with an alternative model.
Keywords: categorization, causal knowledge, conceptual representation, causal model theory, generative modelSupplemental materials: http://dx.doi.org/10.1037/a0019765.supp An important goal in the psychology of concepts is to identify how both empirical information-information that people directly observe-and theoretical beliefs involving explanatory and causal knowledge contribute to how we represent and use categories. Although early research into concepts focused on the effect of empirical information, subsequent research has shown that theoretical beliefs influence many types of category-based judgments, including learning, induction, and categorization (see Murphy, 2002, for a review). In this article, we are concerned with how one type of theoretical knowledge, namely, causal knowledge that relates features of categories, affects one type of category-based judgment, classification.The presence of causal relationships between category features is pervasive. For example, we know that having claws enables tigers to catch prey, having gills enables fish to breathe, and having a fan causes an automobile's engine to remain cool. Not surprisingly then, numerous studies have investigated how this knowledge affects classification. Some studies have tested naturally occurring categories and the real-world causal knowledge that people already possess about those categories (e.g., Ahn, 1998;Kim & Ahn, 2002;Sloman, Love, & Ahn, 1998). However, to conduct precise tests of alternative models, investigators have turned to artificial categories that are subject to greater experimental control. In these studies, participants are instructed on new types of objects and their features and then are taught causal relations among those features. To assess the effect of those causal relations, participants are then asked to judge the category membership of items displaying various combinations of features. Note that although the categories are artificial, they are intended to be plausible, that is, to consist of features and interfeature causal re...