As software engineering research becomes more concerned with the psychological, sociological and managerial aspects of software development, relevant theories from reference disciplines are increasingly critical for understanding the field’s core phenomena of interest. However, the degree to which software engineering research draws on relevant social sciences remains unclear. This study, therefore, investigates the use of social science theories in five influential software engineering journals over 13 years. It examines not only the extent of theory use but also what, how and where these theories are used. While 81 different theories are used, less than two percent of papers use a social science theory, most theories are used in only one paper, most social sciences are ignored, and the theories are rarely tested for applicability to software engineering contexts. In addition, an authors’ survey is conducted to explore the experience and challenges of researchers using social science theories. Software engineering research should make better use of social science theories to avoid oversimplifying and over-rationalizing its core phenomena. More attention to theory is needed for software engineering to mature as a scientific discipline.