The role of exceptions in children's and adults' judgments about generic statements

Generic statements (e.g., “Ducks lay eggs”) provide generalizations about kinds that can be judged as true, even in the face of exceptions. Although past research has focused on the positive evidence that justifies a generic, little work has explored the role of evidence that does not match the generic claim (e.g., ducks that do not lay eggs). The current studies aim to understand how different types of exceptions may differentially undermine generic claims. In Studies 1 and 2, adults (n = 560) and children ages 5–11 (n = 141) were asked to judge the truth of generic statements about fictitious animal kinds (e.g., Wugs have blue horns). Accompanying each statement was a set of 6 kind members, some of which displayed the target property (e.g., blue horns), and others of which displayed either an alternative property (e.g., red horns), or an absence of the property (e.g., no horns). Study 1 found that adults were less likely to endorse generic statements when non-matching examples displayed an alternative property than when they displayed an absence of the property. Study 2 indicated that children as well as adults were less likely to endorse generic statements when presented with alternative evidence, regardless of the salience of the alternative. Study 3 replicated these findings with a more sensitive task in which adults (n = 120) and children (n = 97) were asked to choose between sets with either alternative or absence evidence. These studies provide the first evidence that children and adults attend to non-matching evidence when making judgments about generic statements, interpret alternative evidence to be stronger counterevidence than absence evidence, and do not use the salience of alternative properties to determine the strength of alternative evidence. We discuss the implications of this work for problematic generic claims in language and thought.