Evidence for the Innateness of Deontic Reasoning

When reasoning about deontic rules (what one may, should, or should not do in a given set of circumstances), reasoners adopt a violation-detection strategy, a strategy they do not adopt when reasoning about indicative rules (descriptions of purported state of affairs). I argue that this indicative-deontic distinction constitutes a primitive in the cognitive architecture. To support this claim, I show that this distinction emerges early in development, is observed regardless of the cultural background of the reasoner, and can be selectively disrupted at the neurological level. I also argue that this distinction emerged as a result of selective pressure favouring the evolution of reasoning strategies that determine survival within dominance hierarchies. If seven decades of empirical investigations of human reasoning have shown us nothing else, they have shown us that our reasoning strategies vary as a function of problem content (Byrne, 1989; Cheng and Holyoak, 1985, 1989; Cheng, Holyoak, Nisbett and Oliver, 1986; Cosmides, 1989; Cummins, 1995, in press; Cummins, Lubart, Alksnis and Rist, 1991; Evans, 1989; Griggs and Cox, 1982, 1983; Henle, 1962; Manktelow and Over, 1991; Revlin and Leirer, 1978; Roberge, 1982; Thompson, 1994, 1995; Thompson and Mann, 1995; van Duyne, 1974; Wason, 1968; Wason and Johnson-Laird, 1972; Wason and Shapiro, 1972; Wilkins, 1928). While robust, pervasive, and readily evoked, the significance of content effects is far from clear. Initial explanations attributed them to the idiosyncratic influence of an individual’s knowledge on a content-free, syntactically-driven reasoning process (Braine, 1978; Braine and OBrien, 1991; Henle, 1962; Rumain, Connell and Braine, 1983). In recent years, however, a groundswell of opinion has arisen that it is in the evocation of content effects that the true nature of the human reasoning architecture is to be found. Human reasoning varies as a function of content because the human reasoning architecture consists of a collection of domain-specific Portions of this paper were presented at the Conference for Epistemiology and Evolutionary Psychology, Rutgers Unversity, April, 1995. I thank Nick Chater and David Over for their invaluable comments on an earlier draft of this paper. Address for correspondence: Cognitive Science, Psyihdogy 312, University of Arizona, Tucson, AZ 85721, USA. Email: [email protected]. Deontic Reasoning Modules 161 acquired schemas (Cheng and Holyoak, 1985, 1989; Cheng et al., 1986), evolved modules (Cosmides, 1989; Cosmides and Tooby, 1989, 1992, 1994), or model-building strategies (Johnson-Laird and Byrne, 1991; Manktelow and Over, 1991) rather than a collection of syntactically-driven rules. For this reason, different contents evoke different domain-relevant reasoning strateges. 1. The Indicative-Deontic Distinction in Adult Reasoning One of the most robust content effects in the literature is what I will call the indicative-deontic distinction. Indicative reasoning is reasoning about the epistemic status of rules. It can be analyzed in terms of hypothesis-testing, that is, testing the truth content of a rule that describes a purported state of affairs. Deontic reasoning, on the other hand, is reasoning about what one may, ought, or must not do in a given set of circumstances (Hilpinen, 1971, 1981; Manktelow and Over, 1991). Virtually all of our social institutions presuppose a capacity to understand and reason about what is permitted, obligated, prohibited, cautioned, or advised. Failure to reason effectively about deontic rules can have disastrous consequences, including scolding, expulsion, legal action, and even incarceration. We also presume the capacity to reason deontically in most of our child-rearing and social interactions, appealing to this presumed capacity whenever we utter a permission, promise, warning, or threat. Human reasoners treat these two types of rules very differently, adopting a violation-detecting strategy when reasoning about deontic rules and a confirmation-seeking strategy when reasoning about indicative rules. The clearest examples of the indicative-deontic distinction are based on the Wason card selection task, a task unique not only in its simplicity but in its ability to generate robust content effects (Wason, 1968). This task consists of asking reasoners which of four cards must be turned over in order to test a particular conditional rule (p 4). The four cards correspond, respectively, to the antecedent of the conditional (p), its consequent (q), and the denial of each (not-p, not-q). For example, consider the following problem: A friend relates to you the observation that in Arizona ’If you go to Phoenix, you travel by train.’ In front of you are four cards that have a person’s destination on one side and his or her means of transportation on the other. Your task is to indicate all and only those cards that must be turned over in order to test whether or not your friend was telling the truth. Your choices are ’Phoenix’, ‘Tucson’, ’Train’ and ’Car’. If you are like the vast majority of people, you selected ‘Phoenix‘ and ‘Train‘, that is, p and q. Now consider the following case. You are to pretend that you work for the Arizona transportation bureau, and it is your job to enforce a new law aimed at reducing air pollution due to car emissions. The law is ’If you go to Phoenix, you must travel by train.’ You’re shown the same four cards, and are asked to indicate all and only those cards that must be turned over in order to determine whether or not the rule is being followed. If you’re 0 Blackwell Publishers Ltd. 1996