Universal moral grammar: theory, evidence and the future

Scientists from various disciplines have begun to focus attention on the psychology and biology of human morality. One research program that has recently gained attention is universal moral grammar (UMG). UMG seeks to describe the nature and origin of moral knowledge by using concepts and models similar to those used in Chomsky's program in linguistics. This approach is thought to provide a fruitful perspective from which to investigate moral competence from computational, ontogenetic, behavioral, physiological and phylogenetic perspectives. In this article, I outline a framework for UMG and describe some of the evidence that supports it. I also propose a novel computational analysis of moral intuitions and argue that future research on this topic should draw more directly on legal theory.

Introduction

This article outlines a framework for the study of human moral cognition, currently one of the liveliest topics in the cognitive sciences. The framework has come to be known as universal moral grammar (UMG) 1, 2, 3, 4, 5, 6 because it seeks to describe the nature and origin of moral knowledge by using concepts and models similar to those used in the study of language [7]. UMG shares many features with other important research programs in moral psychology 8, 9, 10, 11, 12, 13, 14, 15, particularly an emphasis on describing the operative principles of intuitive moral judgment and a departure from Kohlberg's [16] once-dominant paradigm, which shifted attention away from moral intuitions and towards the interpretive or ‘hermeneutic’ evaluation of articulate justifications. However, UMG also has certain distinctive characteristics that set it apart from other influential approaches, such as those of Greene [10], Haidt [11], Moll [12] and Sunstein [12]. First, UMG is organized around five main questions (Box 1), each of which has a direct parallel in linguistics and is interpreted in light of concepts that Chomsky used to clarify their linguistic counterparts, such as the distinctions between (i) competence and performance, (ii) descriptive and explanatory adequacy, and (iii) the perception and production problems 17, 18, 19. Second, UMG proceeds from assumptions that are mentalist, modular and nativist 1, 2, 3, 4, 5, 6, 17, 18, 19, 20, 21. Third, in keeping with Marr's [22] analysis of the three levels at which any information-processing task can be understood, UMG focuses special attention on the top level, the level of computational theory. The view it adopts is that, like other domains, an adequate scientific theory of moral cognition will often depend more on the computational problems that have to be solved than on the neurophysiological mechanisms in which those solutions are implemented [22].