What is Special about Children's Deontic Reasoning?

What is Special about Children’s Deontic Reasoning? Monica Bucciarelli (monica@psych.unito.it) Center for Cognitive Science and Department of Psychology, via Po 14, 10123 Torino ITALY Abstract The Mental Model Theory of Deontics The assumption underlying the present investigation is that comprehension and reasoning from deontic premises, as well as comprehension and reasoning from factual premises, depend on mental models, and these models predict what conclusions individuals are likely to draw. Experiment 1 (48 children aged 9-11 years) confirmed the prediction that children’s comprehension of deontic assertions, like their comprehension of factual assertions, relies on models. Experiment 2 (40 children aged 9-11 years) confirmed the prediction that on the basis of the models it is possible to predict developmental changes in the ability to reason from pairs of deontic assertions. The results of the investigation run against the existence of specialized mechanisms for comprehension and reasoning from deontic matters. The mental model theory (MMT) postulates that individuals use the meaning of assertions and general knowledge to construct mental models of the possibilities described by factual assertions (Johnson-Laird, 1983; Johnson-Laird & Byrne, 1991). Each model represents a separate possibility. Hence, a disjunction such as: Either you receive a grade or else you receive a comment, but not both refers to two alternative possibilities that are represented in two mental models. A conventional notation for models lays out each of them on a separate row of a diagram. The two models of the preceding disjunction are as follows: You receive a grade You receive a comment Of course, real mental models are representations of the state of the world, not sentences, which we use here for convenience. MMT is based on a principle of truth, which stipulates that mental models represent only what is true, not what is false. Hence, the two models above represent the possibilities in which the disjunction is true, and each of them represents a clause from the disjunction only when it is true in a possibility. Fully explicit models violate the principle of truth by representing clauses both when they are true and when they are false. Hence, fully explicit models of the disjunction are as follows: You receive a grade ¬You receive a comment ¬You receive grade You receive a comment The symbol ‘¬’ denotes negation, and so models represent false propositions as true negations. MMT readily extends to deontic assertions (Bucciarelli & Johnson-Laird, 2005). There are four main deontic relations, because they exhaust the set of possible dyadic deontic relations: A permits B, A obligates B, A prohibits B, Not A obligates B, where the variables A and B take as their values phrases capturing such propositions as, ‘you make a promise’, and ‘you do what you say’. For example, the assertion Your making a promise obligates you to do what you say, captures a relation between a possibility (you make a promise) and what it obligates (you do what you promise). MMT postulates that such assertions of the form, A obligates B, are consistent with three alternatives: A B ¬ A B ¬ A ¬ B where A and its negation refer to possibilities and B and its negation refer to what is permissible, and where there is a temporal constraint that B doesn’t occur prior to A. Hence, when A occurs and, say, you make a promise, there is only one state of affairs that is subsequently permissible – you do Keywords: deductive reasoning; deontics; mental models; development Introduction Deontic reasoning concerns what is obligatory, permissibile, and impermissible. Many theorists propose that it depends on special mechanisms (see, e.g., Chao & Cheng, 2000; Cosmides, 1989; Cummins, 1996). In this paper, we propose a contrasting theory, which is based on mental models, and which postulates that the mental processes underlying the comprehension of, and reasoning from, deontic propositions (e.g., Children are obligated to go to school) are the same as those for dealing with factual propositions (e.g. Children go to school). The only important difference concerns the content of the propositions: given a true factual proposition, certain states of affairs are impossible; given a true deontic proposition, certain actions or inactions are impermissible, or, we sometimes say, deontically impossible. Alas, what is deontically impossible is all too often factually possible: individuals do not always do the right thing, or refrain from doing the wrong thing. In other words, a counterexample to a factual proposition shows that it is false, whereas a counterexample to a deontic proposition shows that someone has violated the principle it embodies, not that the proposition itself is false. Likewise, the truth of a factual proposition depends on the state of the world, whereas the truth of a deontic proposition is a more complicated matter depending on mores, customs, conventions, and much more besides: one man’s meat is another man’s moral violation. The theory of mental models claims, however, that both factual and deontic propositions are represented in mental models, which have appropriate annotations representing the status of a model as factual or deontic, that the two domains parallel one another both in terms of what tends to be represented and what tends not to be represented, and that they share a common underlying mechanism for reasoning.