Generalization in Legal Argumentation

When interpreting a natural language argument that generalizes over a contextually relevant category, audiences are likely to activate the category prototype and transfer its characteristics onto category instances. A generalized argument can thus appear more (respectively less) persuasive than one mentioning a specific category instance, provided the argument's claim is more (less) warranted for the prototype than for the instance (positiveandnegative prototype effect). To investigate this effect in legal contexts using mock-scenarios, professional and lay judges at Swedish courts evaluated the persuasiveness of arguments giving a generalized or a specific description of an eyewitness. The generalized version described the witness either as analcohol-intoxicated personor as achild, while the specific version varied both theamount of alcoholconsumed (two vs. five glasses of wine) and the child'sage(four vs. 12 years). To investigate the effect of legal expertise on argument selection, moreover, law and social science students evaluate the persuasiveness of both argument versions. Though we observed statistically significant prototype effects as well as expertise effects, results were mixed and sometimes ran counter to normative expectation.