Modules, Minds and Morality

We here engagewith a long-lasting debate in the cognitive sciences concerning domainspecific mechanisms for acquiring and processing different systems of knowledge, focusing on the problem of morality. We ask whether there are mechanisms that uniquely evolved in humans, and uniquely for the domain of morality. We discuss behavioral and neurophysiological evidence that bears on the role of emotions and mental state reasoning in moral cognition. Based on this evidence, wemake a tentative, yet provocative, suggestion: what is unique to the moral domain is unlikely to be the mechanisms that underlie our emotional processing or folk psychology, but rather the ways in which these systems interface to create outputs that are distinctively moral. We begin this essay talking about testes. We realize that this is an uncommon introduction, but we think that studies of testes provide an entry into a central question about the mind and thus the general focus of this essay: what evidence do we have for neuroanatomical specializations for distinct domains of knowledge? The study of testes reveals how you can get anatomical specialization based on particular social and ecological conditions. In the early 1980s, Harcourt and colleagues (1981) made an extremely important discovery. If you plot testes size against themating systems ofmonkeys and apes, yousee a fascinating relationship: species with intense mating competition have larger testes than species with less intense mating competition. Thus, the polygynous chimpanzees have extremely large testes, whereas the monogamous gibbons have extremely small testes. In case you are curious, the size of human testes is closer to chimpanzees than gibbons, revealing what anthropologists have documented over the years: past and current human cultures are mostly polygynous, with monogamy largely a myth or recent cultural invention. The relationship between mating system and testes size is so tight that if you were walking in the woods and found a pair of detached testicles, you would be able to generate a confident prediction about this animal’s mating system. The reason for this relationship falls out of standard Darwinian sexual selection: larger testes allow for greater spermvolume, which is critical in species where there is intense mating competition. Intense mating competition arises when there are few sexually receptive females and many sexually interested males. Here we turn to the general problem of modularity and ask about the nature of domain-specific processing systems (Cosmides and Tooby 1994; Fodor 1983; Gallistel 1999; Sperber 1994) and, especially, the kind of neurophysiological evidence that bears on this problem. Specifically, we explore themoral domain and askwhether this system of knowledge ismediated by a specialized faculty or instead consists of a cluster of either domain-general or domain-specific, but non-moral, mechanisms for acquiring and acting upon moral knowledge (Hauser 2006; Stich 2006). Our road map is as follows. We begin with a brief discussion of face processing, as it provides perhaps one of the strongest cases to date of domain specificity. Though heated discussion continues over the strength of this claim, it is a useful example for our purposes as it clearly lays out the kinds of questions and evidence that must be addressed in making an argument for domain specificity. Second, we provide a framework for thinking about the moral domain that appeals to recent discussion of a different domain: language. In particular, we begin by discussing how theoretical and empirical work on language generates a set of fundamental questions that should be addressed by scholars focusing on any domain of knowledge, includingmorality. Third, we review recent research that highlights how neuroscientific findings contribute to our understanding of not only those processes that are critically involved in generating moral judgments but also the relative timing of such processes. Thus, we explore both the relative contribution of mental state reasoning and emotion and the timing of these processes relative to the delivery of a moral judgment. Many in-depth reviews have recently been written about some of these topics (Casebeer 2003; Greene and Haidt 2002; Haidt 2001, 2007; Hauser 2006; Moll et al. 2007), but here we attempt to put them together in a slightly different light.