This page includes data, code, and materials for the manuscript "*Differentiate to Regulate: Low Negative Emotion Differentiation is Associated with Ineffective Use but Not Selection of Emotion-Regulation Strategies*" to appear in Psychological Science. To navigate the files, consult the index file **Index of Files Included in OSF Storage.docx** ---------------------------- **Abstract** Emotion differentiation, which involves experiencing and labeling emotions in a granular way, has been linked with well-being. It has been theorized that differentiating between emotions facilitates effective emotion regulation, but this link has yet to be comprehensively tested. In two experience-sampling studies, we examined how negative emotion differentiation was related to 1) the selection of emotion-regulation strategies, and 2) the effectiveness of these strategies in down-regulating negative emotion (Ns=200 and 101 participants; 34,660 and 6,282 measurements, respectively). Unexpectedly, we found few relationships between differentiation and the selection of putatively adaptive or maladaptive strategies. Instead, we found interactions between differentiation and strategies in predicting negative emotion. Among low differentiators, all strategies (Study 1) and 4 of 6 strategies (Study 2), were more strongly associated with increased negative emotion than they were among high differentiators. This suggests that low differentiation may hinder successful emotion regulation, which in turn supports the idea that effective regulation may underlie differentiation benefits.