Sarah-Jane Leslie

This chapter distinguishes the clusters of psychologically real heuristics that govern our use of terms—the “psi-concepts”—from the “phi-concepts” or meanings that are the semantic determinants of the extensions of the terms in question, and hence of the truth-conditions of the sentences that contain those terms. Concerning the psi-concepts the chapter proposes a new, empirically motivated, and philosophically consequential amendment to both the theory-theory and the prototype theory, namely the generic encoding hypothesis: the heuristics which typically guide our use of terms by exploiting prevalence, cue-validity, and causal explanatory structure are properly formulated in generic terms. The chapter then explores the philosophical consequences of the generic encoding hypothesis, exploring its destructive impact on the method of cases (with particular attention to its use in the philosophy of personal identity), philosophical analysis, the “normativity of meaning,” and the idea that we know how to use terms by grasping meanings.

How is our perception of the social world shaped by hearing generic generalizations? This chapter reviews evidence from experimental psychology that suggests that generic language leads both preschoolers and adults to view both social groups and abilities in essentialist terms—that is, to think of social categories as reflecting deep, inherent differences between people, and to think of abilities as innate, immutable and unresponsive to hard work and practice. The tendency to view social categories in essentialist terms has been linked to stereotyping and prejudice, and so it is important to understand the cues that lead children to conceive of a given social category in this way. Similarly, thinking of abilities as inherent and unchangeable has been shown to lead to impaired performance, and to increase vulnerability to stereotype threat. Recent findings suggest that hearing generic language may play an important role in the development of both sets of beliefs.

One often ‘relies on intuitions’ in the course of an argument, but what is the epistemological status of these intuitions? Kripke and Putnam famously argued that natural kinds have essences, which are discovered by science, and which determine the extensions of our natural kind terms and concepts. Their arguments make critical use of intuitions—ones which, it is argued in this paper, are traceable to an early-developing cognitive bias/belief set. If we did not have such a cognitive outlook then we would not have the relevant philosophical intuitions. Do natural kinds actually have scientifically discoverable essences, which could determine the extensions of our terms and concepts? Many philosophers of science have argued that natural kinds do not have such essences, but this point has not been properly assimilated. This paper suggests that this is because the Kripke/Putnam view _is just so intuitive_, but that its intuitive appeal derives from our cognitive biases rather than from its being correct.

Psychological essentialism is a folk theory characterized by the belief that a causal internal essence or force gives rise to the common outward behaviors or attributes of a category's members. In two studies, we investigated whether 4- to 7-year-old children evidenced essentialist reasoning about heart transplants by asking them to predict whether trading hearts with an individual would cause them to take on the donor's attributes. Control conditions asked children to consider the effects of trading money with an individual. Results indicated that children reasoned according to essentialism, predicting more transfer of attributes in the transplant condition versus the non-bodily money control. Children also endorsed essentialist transfer of attributes even when they did not believe that a transplant would change the recipient's category membership. This finding runs counter to predictions from a strong interpretation of the “minimalist” position, an alternative to essentialism.

Generic language (e.g., “tigers have stripes”) leads children to assume that the referenced category (e.g., tigers) is inductively informative and provides a causal explanation for the behavior of individual members. In two preregistered studies with 4- to 7-year-old children (N = 497), we considered the mechanisms underlying these effects by testing how correcting generics might affect the development of these beliefs about novel social and animal kinds (Study 1) and about gender (Study 2). Correcting generics by narrowing their scope to a single individual limited beliefs that the referenced categories could explain what their members would be like while broadening the scope to a superordinate category (Study 2) uniquely limited endorsement of gender norms. Across both studies, correcting generics did not alter beliefs about feature heritability and had mixed effects on inductive inferences, suggesting that additional mechanisms (e.g., causal reasoning about shared features) contribute to the development of full-blown essentialist beliefs. These results help illuminate the mechanisms by which generics lead children to view categories as having rich inductive and causal potential; in particular, they suggest that children interpret generics as signals that speakers in their community view the referenced categories as meaningful kinds that support generalization. The findings also point the way to concrete suggestions for how adults can effectively correct problematic generics (e.g., gender stereotypes) that children may hear in daily life.

Much evidence suggests that, from a young age, humans are able to generalize information learned about a subset of a category to the category itself. Here, we propose that—beyond simply being able to perform such generalizations—people are biased to generalize to categories, such that they routinely make spontaneous, implicit category generalizations from information that licenses such generalizations. To demonstrate the existence of this bias, we asked participants to perform a task in which category generalizations would distract from the main goal of the task, leading to a characteristic pattern of errors. Specifically, participants were asked to memorize two types of novel facts: quantified facts about sets of kind members and generic facts about entire kinds. Moreover, half of the facts concerned properties that are typically generalizable to an animal kind, and half concerned properties that are typically more idiosyncratic. We predicted that—because of the hypothesized bias—participants would spontaneously generalize the quantified facts to the corresponding kinds, and would do so more frequently for the facts about generalizable properties. In turn, these generalizations would lead to a higher rate of quantified-to-generic memory errors for the generalizable properties. The results of four experiments supported this prediction. Moreover, the same generalizable-versus-idiosyncratic difference in memory errors occurred even under cognitive load, which suggests that the hypothesized bias operates unnoticed in the background, requiring few cognitive resources. In sum, this evidence suggests the presence of a powerful bias to draw generalizations about kinds

Cognitive science poses a variety of philosophical questions. In this forthcoming volume, leading researchers debate five core questions in the Philosophy of Cognitive Science: Is Universal Grammar required to explain our linguistic capacities? Are some of our concepts innate or are they all learned? What role do our bodies play in cognition? Can neuroscience help us understand the mind? Can cognitive science help us understand human morality? The volume contains two accessible essays on each topic, each advocating for an opposing approach.

Generic sentences (e.g., bare plural sentences such as “dogs have four legs” and “mosquitoes carry malaria”) are used to talk about kinds of things. Three experiments investigated the conceptual foundations of generics as well as claims within the formal semantic approaches to generics concerning the roles of prevalence, cue validity and normalcy in licensing generics. Two classes of generic sentences that pose challenges to both the conceptually based and formal semantic approaches to generics were investigated. Striking property generics (e.g. “sharks bite swimmers”) are true even though only a tiny minority of instances have the property and thus pose obvious problems for quantificational approaches, and they also do not seem to characterize kinds in terms of the principled or statistical connections investigated in previous research ( Prasada and Dillingham, 2006 ; Prasada and Dillingham, 2009). The second class — minority characteristic generics (e.g. “ducks lay eggs”) — also poses serious problems for quantificational accounts, and appears to involve principled connections even though fewer than half of its instances have the relevant property. The experiments revealed three principal discoveries: first, striking generics involve neither principled nor statistical connections. Instead, they involve a causal connection between a kind and a property. Second, minority characteristic generics exhibit the characteristics of principled connections, which suggests that principled connections license the expectation that most instances will have the property, but do not require it. Finally, the experiments also provided evidence that prevalence and the acceptability of generics may be dissociated and provided data that are problematic for normalcy approaches to generics, and for the idea that cue validity licenses low prevalence generics. As such, the studies provided evidence in favor of a conceptually based approach to the semantics of generics ( Leslie, 2007 ; Leslie, 2008; see also Carlson, 2009).

The present paper focuses on essentialism about natural kinds as a case study in order to illustrate this more general point. Saul Kripke and Hilary Putnam famously argued that natural kinds have essences, which are discovered by science, and which determine the extensions of our natural kind terms and concepts. This line of thought has been enormously influential in philosophy, and is often taken to have been established beyond doubt. The argument for the conclusion, however, makes critical use of intuitions, and I note that the intuitions are of the sort had by preschool children, and that they are traceable to a deep-seated cognitive outlook, which is often called “psychological essentialism.” Further, if we did not have such a cognitive outlook or implicit belief set—a belief set which is in fact in place by at least age 4—then we would not have the relevant philosophical intuitions. In light of this, I consider the question of whether natural kinds actually have scientifically discovered or discoverable essences, and whether these putative essences could determine the extensions of our terms and concepts as Kripke, Putnam, and many others have supposed. In fact, a number of philosophers of biology and chemistry have argued that biological and chemical kinds do not have such essences, yet these arguments—particularly in the case of chemistry—have not been assimilated by philosophers more generally. The reason for this poor assimilation is, I suggest, that the Kripke/Putnam view is just so intuitive. But this fact, I argue, is due to a deep-seated cognitive bias, rather than to any special insight into the nature of reality.

Generic generalizations such as ‘mosquitoes carry the West Nile virus’ or ‘sharks attack bathers’ are often accepted by speakers despite the fact that very few members of the kinds in question have the predicated property. Previous work suggests that such low-prevalence generalizations may be accepted when the properties in question are dangerous, harmful, or appalling. This paper argues that the study of such generic generalizations sheds light on a particular class of prejudiced social beliefs, and points to new ways in which those beliefs might be undermined and combatted.