of moral judgment and action through moral commitment. Those with moral goals central to the self-concept are more likely to take moral action, as they feel a greater obligation to do so. Those who are motivated will attain a unique moral identity. Following the independent publication of a pair of landmark papers in 2001 (respectively led by Jonathan Haidt and Joshua Greene), there was a surge in interest in moral psychology across a broad range of subfields of psychology, with interest shifting away from developmental processes towards a greater emphasis on social, cognitive, affective and neural processes involved in moral judgment. Methods Philosophers, psychologists and researchers from other fields have created various methods for studying topics in moral psychology, with empirical studies dating back to at least the 1890s. The methods used in these studies include moral dilemmas such as the trolley problem, structured interviews and surveys as a means to study moral psychology and its development, as well as the use of economic games, neuroimaging, and studies of natural language use. Interview techniques In 1963, Lawrence Kohlberg presented an approach to studying differences in moral judgment by modeling evaluative diversity as reflecting a series of developmental stages (à la Jean Piaget). Lawrence Kohlberg's stages of moral development are: Obedience and punishment orientation Self-interest orientation Interpersonal accord and conformity Authority and social-order maintaining orientation Social contract orientation Universal ethical principles Stages 1 and 2 are combined into a single stage labeled "pre-conventional", and stages 5 and 6 are combined into a single stage labeled "post-conventional" for the same reason; psychologists can consistently categorize subjects into the resulting four stages using the "Moral Judgement Interview" which asks subjects why they endorse the answers they do to a standard set of moral dilemmas. Survey instruments Between 1910 and 1930, in the United States and Europe, several morality tests were developed to classify subjects as either fit or unfit to make moral judgments. Test-takers would classify or rank standardized lists of personality traits, hypothetical actions, or pictures of hypothetical scenes. As early as 1926, catalogs of personality tests included sections specifically for morality tests, though critics persuasively argued that they merely measured intelligence or awareness of social expectations. Meanwhile, Kohlberg inspired a new series of morality tests. The Defining Issues Test (dubbed "Neo-Kohlbergian" by its constituents) scores relative preference for post-conventional justifications, and the Moral Judgment Test scores consistency of one's preferred justifications.