Explanations make inconsistencies harder to detect

Explanations make inconsistencies harder to detect Sangeet Khemlani and P.N. Johnson-Laird {khemlani, phil}@princeton.edu Department of Psychology Princeton University Princeton, NJ 08540 USA Abstract they judge how well concepts cohere with one another (Murphy & Medin, 1985; Palatano, Chin-Parker, & Ross, 2006). We propose that an additional function of explanatory reasoning is to resolve inconsistencies. What role do explanations play in reasoning about inconsistencies? We postulate that when people create explanations, they use them to resolve conflicting information. This hypothesis predicts that inconsistencies should be harder to detect once individuals have in mind an explanation of the inconsistency. We report four experiments that tested this prediction. Experiments 1a and 1b corroborated the effect when participants made inferences from inconsistent assertions. Experiment 2 compared the effect of explanations of inconsistencies with those of a similarly demanding task. Experiment 3 ruled out a potential confound. Explanations resolve inconsistencies Keywords: inconsistency, explanations, belief revision, reasoning, principle of resolution Introduction The word ‘why’ is used to elicit explanations for the mysteries of daily life. Why is my car making that noise? Why didn’t the Redskins win last Sunday? Why isn’t my experiment working? Indeed, a central feature of human rationality is the ability to construct explanations of observed behaviors and phenomena (Harman, 1965). Recent research has explored the function and developmental trajectory of explanatory reasoning (Keil, 2006; Wellman, Hickling, & Schult, 1997). There is consensus among researchers that explanations are related to causal inference (Johnson-Laird, Girotto, & Legrenzi, 2004; Sloman, 2005; Walsh & Johnson-Laird, 2009), and that explanations impact reasoning, categorization, and learning (Lombrozo, 2006). Less is known about the contexts under which explanations are generated, i.e., it is unclear when and how individuals decide to produce explanations. How do you reveal what a person understands about some subject matter? One way is to ask the person to explain it, because explanations require individuals to communicate their knowledge and beliefs about the phenomenon in question. Explanations can also occur in other tasks that draw upon general knowledge. For instance, explanations are useful when you are learning new information (Amsterlaw & Wellman, 2006; Chi, De Leeuw, Chiu, & Lavancher, 1994; Crowley & Siegler, 1999; Rittle-Johnson, 2006), and they help to predict future behaviors (Anderson & Ross, 1980; Einhorn & Hogarth, 1986; Lombrozo & Carey, 2006; Ross, Lepper, Strack, & Steinmetz, 1977). Individuals spontaneously produce explanations when they try to form categories (Shafto & Coley, 2003) and when Consider the following: If people are tired then they go to sleep. A person was tired, but he did not go to sleep. The two assertions are inconsistent, i.e., they cannot both be true. Given such an inconsistency, it is felicitous to ask: “why not? ” But the same question is infelicitous when the assertions are obviously consistent with one another: If people are tired then they go to sleep. A person was not tired, and he did not go to sleep. It seems strange to elicit an explanation for consistent assertions, and reasoners are likely to balk at such a request. Thus, an inconsistency calls for people to search for explanations, while an explanation is less appropriate when expectations are met. We hypothesize that individuals resolve a set of inconsistent causal assertions by using an explanation to interpret each assertion, a view we call the principle of resolution. The principle assumes that when an inconsistency is detected among a set of assertions, reasoners construct explanations to restore consistency to the set (Johnson-Laird et al., 2004). They then interpret the assertions based on the consequences of the explanations. Consider the inconsistency above. One explanation for the person not going to sleep is that he was under some deadline, and so pursued his work despite his fatigue. The explanation provides an exception to the generalization that if people are tired they go to sleep. However, instead of abandoning it, reasoners are likely to construe it as an idealization that holds by default: it is true in many cases, but tolerates exceptions. The assertion may be interpreted as something akin to the generic assertion, i.e., ‘people who are tired go to sleep’ (Khemlani, Leslie, Glucksberg, & Rubio- Fernandez, 2007; Leslie, 2008). The principle of resolution thus allows individuals to use explanations to resolve inconsistencies by weakening the initial interpretation to that of an idealization rather than a universal truth. One potential side effect of the principle is that when reasoners have an explanation of an inconsistency in mind, they may overlook the inconsistency on subsequent assessments of the assertions. If they interpret the conditional as an idealization, their new interpretation may