How Many Moralities? a Bottom-Up Approach to Mapping the Brain’s Natural Moral Categories

Abstract

The external structure and internal boundaries of the moral domain are not sharply defined. Substantive definitions of morality struggle to cleanly encapsulate the full diversity of human moral concern without including too much to retain correspondence to folk understandings, while functionalist definitions are complex and difficult to implement in study. Psychological work in 20th century often assumed morality was a single domain concerned primarily with transgression types emphasized in Western academia. Recent brain-imaging work has suggested that morality may in fact comprise multiple sub-domains, corresponding to moral natural kinds which cover a more diverse spectrum of topics than Western morality is typically concerned with (Parkinson et al., 2011). Moral Foundations Theory (MFT), which takes an evolutionary functionalist approach, is a promising candidate structure for this expanded moral domain. Here I probe the structure of the moral domain in exploratory fashion for correlates to the foundations of MFT in patterns of brain activation in response to moral stimuli generated and categorized by survey respondents. Activation contrasts are used to identify regions of differential activity between the putative foundations. Conjunctive overlaps between foundation contrasts are compared in order to establish which foundations behave similarly to one another relative to the other foundations in the set. Neither the 5-factor structure of MFT nor its coarser 2-factor structure is upheld. Instead, a semi-polarized scheme is suggested, with harm-preventative and purity-maintaining moral types occupying the extremes and more interpersonal foundations grouped together in between and less clearly delineated than previously assumed.