Academic journal article Memory & Cognition

Iffy Beliefs: Conditional Thinking and Belief Change

Academic journal article Memory & Cognition

Iffy Beliefs: Conditional Thinking and Belief Change

Article excerpt

The ability to entertain possibilities and draw inferences about them is essential to human intelligence. We examine the hypothesis that conditional if-then statements trigger a mental simulation process in which people suppose the antecedent (if statement) to be true and evaluate the consequent (then statement) in that context. On the assumption that supposing an event to be true increases belief that the event has occurred or will occur, this hypothesis is consistent with the claim that evaluating a conditional will heighten belief in its antecedent more than in its consequent. Two experiments, employing conditionals of the form If animal A has property X, then animal B will have property X, in which X was a property that people could not readily relate to the animals, supported this claim. The effect was stronger following the evaluation of conditionals with dissimilar animal categories.

People frequently consider hypothetical possibilities (such as What if true peace is achieved in the Middle East?) and even counterfactual possibilities (such as What if true peace had been achieved in the Middle East prior to 2001?). Even children love the "what if" game. What these kinds of thoughts have in common is that they concern other possibilities; they involve drawing inferences about a possibility that is different from the one we experience. How people consider such possibilities is the subject of work on pretense (see, e.g., Nichols & Stich, 2000), fantasy (see, e.g., Markovits, 1995), counterfactual thought (see, e.g., Byrne, 2002), causal learning and inference (Sloman, 2005), and conditional reasoning (see, e.g., Evans & Over, 2004). Work on conditional reasoning is perhaps the most general, since it concerns how people draw inferences that are conditioned on some assumption-in other words, how we reason about if-then statements. All studies of reasoning about possibilities can be framed this way.

A recent theory of how we reason about if-then statements, the suppositional theory of conditionals (Evans & Over, 2004; Evans, Over, & Handley, 2005; Handley, Evans, & Thompson, 2006), suggests that conditionals cue a mental simulation in which people suppose the antecedent (if statement) to be true and then assess their degree of belief in the consequent (then statement). This theory is based on what philosophical logicians have called the Ramsey test (Ramsey, 1931, 1990), which bears resemblance to the simulation heuristic (Kahneman & Tversky, 1982).

Consider, for example, the conditional

If global warming continues, then the economy of Africa will be threatened. (1)

According to the suppositional theory, the starting point for assessing belief in this conditional is to think about a possibility in which global warming continues. One may then consider the causes and consequences of global warming (e.g., increased carbon dioxide pollution, changes in the amount of rainfall) and their effects on crops and animals. For example, increased carbon dioxide pollution might cause coral reefs to die, which in turn would threaten fisheries and income from tourism. This train of thought is one of many that might occur in the process of evaluating a conditional of this kind, but the key point is that whatever belief one might have regarding this conditional, generating that belief depends on hypothetical thinking. Specifically, it depends on a mental simulation in which the antecedent is imagined as reality and its consequences inferred and evaluated.

One implication of this theory is that people evaluate the truth of a conditional as a function of the probability of its consequent in light of its antecedent. This claim has been supported in studies that have examined the relationship between conditional evaluations and self-generated or presented truth table distributions (Evans, Handley, & Over, 2003; Oberauer & Wilhelm, 2003; Over & Evans, 2003; Over, Hadjichristidis, Evans, Handley, & Sloman, 2007). …

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