Jean-François Bonnefon and Denis J. Hilton. Dynamiques Socio-Cognitives et Vie Politique, Université Toulouse-2,. 5 allées Antonio Machado, 34058 Toulouse ...
Getting the Point of Conditionals : An Argumentative Approach to the Psychological Interpretation of Conditional Premises Jean-François Bonnefon and Denis J. Hilton Dynamiques Socio-Cognitives et Vie Politique, Université Toulouse-2, 5 allées Antonio Machado, 34058 Toulouse Cedex, France {bonnefon, hilton}@univ-tlse2.fr
Abstract. Processes that govern the interpretation of conditional statements by lay reasoners are considered a key-issue by nearly all reasoning psychologists. An argumentative approach to interpretation is outlined, based on the idea that one has to retrieve the intention of the speaker to interpret a statement, and an argumentative based typology of conditionals is offered. Some empirical support to the approach is provided, as well as some theoretical support from an evolutionary perspective.
1 Introduction Whatever the theoretical divergences between psychologists interested in conditional reasoning, there is reasonable agreement on at least one point: We will never obtain a satisfying account of conditional reasoning without some idea on the way human reasoners interpret conditional statements before reasoning per se takes place. That is, we need to specify the pragmatic processes that turn a conditional statement into the mental premise that will serve as the input of reasoning proper. While there is agreement on the importance of these pragmatic processes, it is less clear what the word “pragmatic” is taken for. Yet, broadly speaking, it seems that in the context of reasoning psychology, “pragmatics” refers to the way reasoners use their background knowledge to enrich, restrict, or transform the premise set they are given by means of conversational implicatures. While we firmly believe this kind of pragmatic processes to be indeed at work in reasoning in general and in conditional reasoning in particular (see [1], [2], [3]), we will suggest in the present paper that our understanding of conditional reasoning would benefit from a broader conception of the pragmatics of reasoning, a conception that would include considerations about speaker’s intention and illocutionary uptake. In Section 2, we outline our proposal, and suggest that in reasoning situations, considerations of illocutionary force can be handled within an argumentative framework, which allows us to offer a very simple typology of conditional statements. Section 3 is devoted to recent experimental observations and the way we can account for those using this typology. Lastly, Section 4 summarises our contribution and offer some evolutionary perspective on the idea that “domain-general” reasoning is of ar-
gumentative nature, and that interpretation processes are rooted in the activity that consists in extracting arguments from the discourse of others.
2 To Interpret a Conditional Statement is to Get its Point We begin by suggesting that in order to interpret a conditional statement, one has to retrieve the claim it is making. We then offer a typology of conditionals based on the argumentative conventions they are associated to. 2.1 The Intention of the Speaker in a Reasoning Situation In our daily lives, a large part of those conditional premises we use to reason come from conversations, or situations that we treat like conversations. (As argued in [4], “many of our everyday inferences are made from premises that we read or hear from various sources”.) Even when a situation does not (or is not supposed to) have any salient conversational feature, as it is the case with most of experimental reasoning tasks, lay people treat the premises they are given as if they were contributions to a conversation [1]. As contributions to a conversation, conditional statements have points. That is, the speaker asserting a conditional has the intention of achieving some effect by mean of this assertion. The “illocutionary force” of a conditional statement refers to the effect its assertion is intended to achieve. Correct uptake on the addressee’s side demands the retrieval of this illocutionary force: That is, in order to interpret a conditional statement, a reasoner has to understand what was the intention of the speaker who asserted it. Generally speaking, conversation is so ubiquitous that a speaker may have any of a large number of possible intentions – e.g., to inform, to threaten, to apologize, etc. But reasoning situations are more specific in that they greatly narrow the array of possible intentions on the speaker’s side: When it is manifest that the speaker expects the addressee to reason (i.e., to derive a conclusion) from a statement, the addressee can assume the intention to be argumentative. That is, when a statement is meant to be used in reasoning, its contribution to the conversation takes the form of an incitation to a conclusion. Let us call the “claim” of a statement the conclusion it is an incitation for. To illustrate this specificity of reasoning situations, let us consider the two following examples of conditional statements: (1)
If you’re fond of Asian food, I know of a wonderful Vietnamese restaurant not far from your place.
(2)
If you use adult websites at work, you'll be fired.
Addressee of statement (1) is not expected to engage into any conditional reasoning. The contribution of statement (1) to a conversation would most probably be to inform the addresse of the existence of such a restaurant, the if-clause being merely mentioning some condition for the then-clause to be conversationally relevant [5]. On the
other hand, statement (2) clearly is an incitation to a conclusion: It is claiming that the addressee had better not visit adult websites at work, a conclusion that the addressee has to calculate for him(her)self. We have stressed the importance of retrieving the intention of the speaker in order to interpret a conditional statement. We have suggested that in reasoning situations, this intention can be assumed to be of argumentative nature. This greatly simplifies the reasoner’s interpretative task: All (s)he has to do to get the point of the conditional is to get its claim, that is, to understand what is the conclusion the speaker is arguing for or against. The task is made even more simpler by the restricted set of conventional argumentative uses of conditional statements. A tentative typology of those conventional uses is offered in the next section. 2.2 An Argumentation-Based Typology of Conditionals We can basically make to broad kinds of points: points about beliefs (theoretical reasoning) or points about actions (practical reasoning). Similarly, it seems there are two main types of conditional arguments: arguments pointing to the truthfulness of a belief and arguments pointing to the appropriateness of an action. Epistemic conditionals (dealing with beliefs) have received most of the attention of reasoning researchers. Example are numerous and sometimes extremely famous, as “if it is a bird, then it flies”. Such a conditional is claiming that its consequent is true, provided that its antecedent is the case. If no information is available about whether or not the antecedent is the case, the conditional has no claim and will not be used in reasoning. A special subcategory of epistemic conditionals is what we have dubbed [3] the preconditional statement. A preconditional statement is of the form “if (prerequisite of the conclusion) then (conclusion)”. The claim of this statement is actually that the prerequisite is not the case (and therefore that the conclusion cannot be the case, more on this in Section 3). Practical conditionals (dealing with actions) come in two types: the consequential conditional and the conditional instruction. The conditional instruction is of the form “if (event) then (action)”. Its analysis in terms of speaker’s intention is rather more complex than those of other conditionals, see [6] for a detailed exposition. The consequential conditional is of the form “if (action) then (outcome)”. Its standpoint is that the action is either appropriate or not, depending on the valence of the outcome: If the outcome is desirable (viz. undesirable), the action is appropriate (viz. inappropriate). Note that two out of those four types of arguments are self-sufficient, in that sense that they do not need any further premise to make their claim: While the basic epistemic conditional and the conditional instruction need some additional categorical premise to allow a conclusion, consequential conditionals and preconditionals make a claim on their own. Section 3 will focus on experiments involving those two interesting categories, that lead to inferential behaviours that would be somewhat puzzling from a strict deductive point of view. It should be clear now what we believe reasoners to do when they interpret a conditional premise: Reasoners retrieve the claim of the statement by relying on the ar-
gumentative conventions associated to the type they identified the conditional with. Remember the example: “If you use adult websites at work, you’ll be fired.” This conditional is immediately identified as a consequential conditional with an undesirable outcome: It is therefore interpreted as making the claim that using adult websites at work is an inappropriate action. From our interpretational framework, we can derive predictions about what inferences reasoners will derive when confronted to simple problems involving various types of conditionals, which is the focus of the next section.
3 Experimental Observations To illustrate the predictions that can be derived from our interpretational framework, we briefly present some data relevant to preconditionals (Section 3.1) and consequential conditionals (Section 3.2).
3.1 Preconditionals The consideration of the “preconditional” subcategory of conditional statements was actually driven by experimental observations. Byrne [7] was the first to present subject with problems of the form: “If A then C; if (precondition of C) then C”; A.” She then observed that less than 40% of reasoners endorsed the conclusion C from these premises. For example, when presented with the following problem, less than 35% of participants endorsed the conclusion “Mary will study late at the library”: “If Mary has an essay to write then she will study late at the library, If the library stays open late then she will study late at the library, Mary has an essay to write.” From a deductive point of view, reasoners should derive the conclusion C – but according to our argumentative approach to interpretation, there is an explanation why they do not. Reasoners first retrieve the claims of the various arguments they can isolate in the premise set. Here the first (epistemic conditional) and third (categorical) premises of the set constitute an argument supporting the conclusion C. But the second premise is a preconditional whose claim is that the precondition for C might not be satisfied1: it is thus an argument against the conclusion C. Thus reasoners interpret the premise set as containing one argument in favour of C and one argument against it: It is then no longer surprising that the endorsement rate of C falls well below 100%. Experimental support to this explanation can be found in [3]: It is reported there that 60 students were presented with various problems of the form above. They rated on a 7-point scale (from “no chance to be true” to “certainly true”) the confidence
1
The rationale for this claim is detailed in [2] and [3].
they had in the conclusion C, and said if, in their opinion, the second conditional was meant to convey the idea that chances were for the precondition not to be satisfied. Almost 80% of participants judged that the preconditional statement was indeed meant to convey the idea that chances were for the precondition not to be satisfied. More importantly, participants judging so were also the ones that gave the conclusion C a low confidence rating, whereas participant not judging so granted C a normal confidence rating (i.e., comparable to the rating they would have given in the absence of the preconditional). 3.2 Consequential Conditionals Just like preconditionals, consequential conditionals can make a claim on their own, without the need for a categorical premise. This property paves the way for interesting problems – consider the following premise set: “If Marie’s TV is broken, she will have it fixed, If Marie has her TV fixed, she will not be able to pay the electricity bill, Marie’s TV is broken.” Will Marie have her TV fixed? Deductively speaking, she will, and she will not be able to pay the bill. But our argumentative interpretational framework makes another prediction. The first and third premises of the set are a standard epistemic argument in favour of the conclusion “Marie will have her TV fixed”. Yet, the second conditional is of consequential nature, with an undesirable outcome: its claim is thus that the action considered in its if-part (having the TV fixed) is inappropriate. Reasoners are then left with one argument in favour of the conclusion and one argument against it. Endorsement rate of the conclusion should therefore fall again well below 100%, and so was observed in [8]. Endorsement rate was never higher than 40% when the outcome of the consequential was clearly negative. In another experiment, endorsement rates were intermediate (around 55%) when the outcome was only mildly undesirable.
4 Conclusion We have argued that for a reasoner to interpret a conditional statement is to get the point the conditional is making, that is, to retrieve the claim the speaker intended to make. This task is made simple by the fact that there are only a few possible conditional argumentative conventions: We listed four, divided into two main types (epistemic and practical). This typology can account for a variety of experimental phenomena. At the core of our proposal is the idea that interpretation processes are strongly determined by social activity: We interpret premises of a conditional reasoning problem as we would consider the arguments of one that would try to convince us either of the truth of a belief or of the appropriateness of an action. As a final word, we would like to stress that this postulate can receive theoretical support from evolutionary psychology.
Evolutionary psychologists find it implausible that the human mind would have evolved some domain-general reasoning ability [9]. Such an ability would probably suffer from fatal flaws compared to domain and task-specific mechanisms (in terms of speed and accuracy). Yet, Sperber [10] [11] has suggested that one plausible evolved general ability would be the logico-argumentative skills needed to persuade others and not to be too easily persuaded by others. It is argued in [11] that: “It is generally taken for granted that the logical and inferential vocabulary is – and presumably emerged – as tools for reflection and reasoning. From an evolutionary point of view, this is not particularly plausible. The hypothesis that they emerged as tools of persuasion may be easier to defend.” Accordingly, we believe the words if and then to be rooted in persuasion rather than in philosophical logic. Hence, it should not be surprising that lay reasoners interpret conditionals as pieces of persuasive argumentation rather than pieces of logical reasoning.
References 1.
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