The origins of moral psychology can be traced back to early philosophical works, largely concerned with moral education, such as by Plato and Aristotle in Ancient Greece,[18][19] as well as from the Buddhist[20] and Confucian traditions.[21][22][23] Empirical studies of moral judgment go back at least as far as the 1890s with the work of Frank Chapman Sharp,[24] coinciding with the development of psychology as a discipline separate from philosophy. Since at least 1894, philosophers and psychologists attempted to empirically evaluate the morality of an individual,[25][26] especially attempting to distinguish adults from children in terms of their judgment, but these efforts failed because they "attempted to quantify how much morality an individual had—a notably contentious idea—rather than understand the individual's psychological representation of morality".[27]: 284
[I]f you said that you studied moral psychology in the 1980s, then you probably studied the development of moral reasoning. You didn't need to agree with Kohlberg on any particular claim, but you lived and worked on land that Kohlberg had cleared.
Jonathan Haidt[28]: 282
In most introductory psychology courses, students learn about moral psychology by studying the psychologist Lawrence Kohlberg,[29][30][31] who proposed a highly influential theory of moral development, developed throughout the 1950s and 1960s. This theory was built on Piaget's observation that children develop intuitions about justice that they can later articulate. Kohlberg proposed six stages broken into three categories of moral reasoning that he believed to be universal to all people in all cultures.[32] The increasing sophistication of justice-based reasoning was taken as a sign of development. Moral cognitive development, in turn, was assumed to be a necessary (but not sufficient) condition for moral action.[33]
But researchers using the Kohlberg model found a gap between what people said was most moral and actions they took. In response, Augusto Blasi proposed his self-model[34] that links ideas 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.[35]
Following the independent publication of a pair of landmark papers in 2001 (respectively led by Jonathan Haidt and Joshua Greene),[36][37] 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.[