Susan Gelman

Generic statements express generalizations about categories. Current theories suggest that people should be especially inclined to accept generics that involve threatening information. However, previous tests of this claim have focused on generics about non-human categories, which raises the question of whether this effect applies as readily to human categories. In Experiment 1, adults were more likely to accept generics involving a threatening property for artifacts, but this negativity bias did not also apply to human categories. Experiment 2 examined an alternative hypothesis for this result, and Experiments 3 and 4 served as conceptual replications of the first experiment. Experiment 5 found that even preschoolers apply generics differently for humans and artifacts. Finally, Experiment 6 showed that these effects reflect differences between human and non-human categories more generally, as adults showed a negativity bias for categories of non-human animals, but not for categories of humans. These findings suggest the presence of important, early-emerging domain differences in people's judgments about generics.

Generic statements (e.g., “Birds lay eggs”) express generalizations about categories. In this paper, we hypothesized that there is a paradoxical asymmetry at the core of generic meaning, such that these sentences have extremely strong implications but require little evidence to be judged true. Four experiments confirmed the hypothesized asymmetry: Participants interpreted novel generics such as “Lorches have purple feathers” as referring to nearly all lorches, but they judged the same novel generics to be true given a wide range of prevalence levels (e.g., even when only 10% or 30% of lorches had purple feathers). A second hypothesis, also confirmed by the results, was that novel generic sentences about dangerous or distinctive properties would be more acceptable than generic sentences that were similar but did not have these connotations. In addition to clarifying important aspects of generics’ meaning, these findings are applicable to a range of real-world processes such as stereotyping and political discourse

Psychological essentialism is an intuitive folk belief positing that certain categories have a non-obvious inner “essence” that gives rise to observable features. Although this belief most commonly characterizes natural kind categories, I argue that psychological essentialism can also be extended in important ways to artifact concepts. Specifically, concepts of individual artifacts include the non-obvious feature of object history, which is evident when making judgments regarding authenticity and ownership. Classic examples include famous works of art (e.g., the Mona Lisa is authentic because of its provenance), but ordinary artifacts likewise receive value from their history (e.g., a worn and tattered blanket may have special value if it was one’s childhood possession). Moreover, in some cases, object history may be thought to have causal effects on individual artifacts, much as an animal essence has causal effects. I review empirical support for these claims and consider the implications for both artifact concepts and essentialism. This perspective suggests that artifact concepts cannot be contained in a theoretical framework that focuses exclusively on similarity or even function. Furthermore, although there are significant differences between essentialism of natural kinds and essentialism of artifact individuals, the commonalities suggest that psychological essentialism may not derive from folk biology but instead may reflect more domain-general perspectives on the world

Disease transmission is a fruitful domain in which to examine how scientific and folk theories interrelate, given laypeople’s access to multiple sources of information to explain events of personal significance. The current paper reports an in-depth survey of U.S. adults’ causal reasoning about two viral illnesses: a novel, deadly disease that has massively disrupted everyone’s lives, and a familiar, innocuous disease that has essentially no serious consequences. Participants received a series of closed-ended and open-ended questions probing their reasoning about disease transmission, with a focus on causal mechanisms underlying disease contraction, transmission, treatment, and prevention; non-visible biological processes; and ontological frameworks regarding what kinds of entities viruses are. We also assessed participants’ attitudes, such as their trust in scientific experts and willingness to be vaccinated. Results indicated complexity in people’s reasoning, consistent with the co-existence of multiple explanatory frameworks. An understanding of viral transmission and viral replication existed alongside folk theories, placeholder beliefs, and lack of differentiation between viral and non-viral disease. For example, roughly 40% of participants who explained illness in terms of the transmission of viruses also endorsed a non-viral folk theory, such as exposure to cold weather or special foods as curative. Additionally, participants made use of competing modes of construal when explaining how viruses operate, such as framing the immune system response as cells trying to fight off the virus. Indeed, participants who displayed greater knowledge about viral transmission were significantly more likely to anthropomorphize bodily processes. Although comparisons of COVID-19 and the common cold revealed relatively few differences, the latter, more familiar disease elicited consistently lower levels of accuracy and greater reliance on folk theories. Moreover, for COVID-19 in particular, accuracy positively correlated with attitudes, self-protective behaviors, and willingness to be vaccinated. For both diseases, self-assessed knowledge about the disease negatively predicted accuracy. The results are discussed in relation to challenges for formal models of explanatory reasoning.

Psychological essentialism is the belief that some internal, unseen essence or force determines the common outward appearances and behaviors of category members. We investigated whether reasoning about transplants of bodily elements showed evidence of essentialist thinking. Both Americans and Indians endorsed the possibility of transplants conferring donors' personality, behavior, and luck on recipients, consistent with essentialism. Respondents also endorsed essentialist effects even when denying that transplants would change a recipient's category membership (e.g., predicting that a recipient of a pig's heart would act more pig-like but denying that the recipient would become a pig). This finding runs counter to predictions from the strongest version of the “minimalist” position (Strevens,2000), an alternative to essentialism. Finally, studies asking about a broader range of donor-to-recipient transfers indicated that Indians essentialized more types of transfers than Americans, but neither sample essentialized monetary transfer. This suggests that results from bodily transplant conditions reflect genuine essentialism rather than broader magical thinking

Adults report that moral characteristics—particularly widely shared moral beliefs—are central to identity. This perception appears driven by the view that changes to widely shared moral beliefs would alter friendships and that this change in social relationships would, in turn, alter an individual's personal identity. Because reasoning about identity changes substantially during adolescence, the current work tested pre- and post-adolescents to reveal the role that such changes could play in moral cognition. Experiment 1 showed that 8- to 10-year-olds, like adults, judged that people would change more after changes to their widely shared moral beliefs (e.g., whether hitting is wrong) than after changes to controversial moral beliefs (e.g., whether telling prosocial lies is wrong). Following up on this basic effect, a second experiment examined whether participants regard all changes to widely shared moral beliefs as equally impactful. Adults, but not children, reported that individuals would change more if their good moral beliefs (e.g., it is not okay to hit) transformed into bad moral beliefs (e.g., it is okay to hit) than if the opposite change occurred. This difference in adults was mediated by perceptions of how much changes to each type of belief would alter friendships. We discuss implications for moral judgment and social cognitive development.

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

Although traditional economic models posit that money is fungible, psychological research abounds with examples that deviate from this assumption. Across eight experiments, we provide evidence that people construe physical currency as carrying traces of its moral history. In Experiments 1 and 2, people report being less likely to want money with negative moral history. Experiments 3–5 provide evidence against an alternative account that people's judgments merely reflect beliefs about the consequences of accepting stolen money rather than moral sensitivity. Experiment 6 examines whether an aversion to stolen money may reflect contamination concerns, and Experiment 7 indicates that people report they would donate stolen money, thereby counteracting its negative history with a positive act. Finally, Experiment 8 demonstrates that, even in their recall of actual events, people report a reduced tendency to accept tainted money. Altogether, these findings suggest a robust tendency to evaluate money based on its moral history, even though it is designed to participate in exchanges that effectively erase its origins.

When do descriptive regularities become prescriptive norms? We examined children's and adults' use of group regularities to make prescriptive judgments, employing novel groups that engaged in morally neutral behaviors. Participants were introduced to conforming or non-conforming individuals. Children negatively evaluated non-conformity, with negative evaluations declining with age. These effects were replicable across competitive and cooperative intergroup contexts and stemmed from reasoning about group regularities rather than reasoning about individual regularities. These data provide new insights into children's group concepts and have important implications for understanding the development of stereotyping and norm enforcement.

Children and adults commonly produce more generic noun phrases (e.g., birds fly) about animals than artifacts. This may reflect differences in participants’ generic knowledge about specific animals/artifacts (e.g., dogs/chairs), or it may reflect a more general distinction. To test this, the current experiments asked adults and preschoolers to generate properties about novel animals and artifacts (Experiment 1: real animals/artifacts; Experiments 2 and 3: matched pairs of maximally similar, novel animals/artifacts). Data demonstrate that even without prior knowledge about these items, the likelihood of producing a generic is significantly greater for animals than artifacts. These results leave open the question of whether this pattern is the product of experience and learned associations or instead a set of early-developing theories about animals and artifacts.

Generic statements express generalizations about categories and present a unique semantic profile that is distinct from quantified statements. This paper reports two studies examining the development of children's intuitions about the semantics of generics and how they differ from statements quantified by all, most, and some. Results reveal that, like adults, preschoolers recognize that generics have flexible truth conditions and are capable of representing a wide range of prevalence levels; and interpret novel generics as having near-universal prevalence implications. Results further show that by age 4, children are beginning to differentiate the meaning of generics and quantified statements; however, even 7- to 11-year-olds are not adultlike in their intuitions about the meaning of most-quantified statements. Overall, these studies suggest that by preschool, children interpret generics in much the same way that adults do; however, mastery of the semantics of quantified statements follows a more protracted course

We propose that there is a powerful human disposition to track the actions and possessions of agents. In two experiments, 3-year-olds and adults viewed sets of objects, learned a new fact about one of the objects in each set , and were queried about either the taught fact or an unrelated dimension immediately after a spatiotemporal transformation, and after a delay. Adults uniformly tracked object identity under all conditions, whereas children tracked identity more when taught ownership versus labeling information, and only regarding the taught fact . These findings suggest that the special attention that children and adults pay to agents readily extends to include inanimate objects. That young children track an object's history, despite their reliance on surface features on many cognitive tasks, suggests that unobservable historical features are foundational in human cognition

Generic noun phrases (e.g. 'bats live in caves') provide a window onto human concepts. They refer to categories as 'kinds rather than as sets of individuals. Although kind concepts are often assumed to be universal, generic expression varies considerably across languages. For example, marking of generics is less obligatory and overt in Mandarin than in English. How do universal conceptual biases interact with language-specific differences in how generics are conveyed? In three studies, we examined adults' generics in English and Mandarin Chinese. The data include child-directed speech from caregivers interacting with their 19-23-month-old children. Examples of generics include: 'baby birds eat worms' (English) and da4 lao3shu3 yao3 bu4 yao3 ren2 ('do big rats bite people or not?') (Mandarin). Generic noun phrases were reliably identified in both languages, although they occurred more than twice as frequently in English as in Mandarin. In both languages, generic usage was domain-specific, with generic noun phrases used most frequently to refer to animals. This domain effect was specific to generics, as non-generic noun phrases were used most frequently for artifacts in both languages. In sum, we argue for universal properties of 'kind' concepts that are expressed with linguistically different constructions. However, the frequency of expression may be influenced by the manner in which generics are expressed in the language.

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.

Money can take many forms—a coin or a bill, a payment for an automobile or a prize for an award, a piece from the 1989 series or the 2019 series, and so on—but despite this, money is designed to represent an amount and only that. Thus, a dollar is a dollar, in the sense that money is fungible. But when adults ordinarily think about money, they think about it in terms of its source, and in particular, its moral source (e.g., dirty money). Here we investigate the development of the belief that money carries traces of its moral history. We study children ages 5–6 and 8–9, who are sensitive to both object history and morality, and thus possess the component pieces needed to think that a dollar may not be like any other. Across three principal studies (and three additional studies in Appendix S1; N = 327; 219 five‐ and six‐year‐olds; 108 eight‐ and nine‐year‐olds), we find that children are less likely to want money with negative moral history, a pattern that was stronger and more consistent among 8‐ and 9‐year‐olds than 5‐ and 6‐year‐olds. These findings highlight pressing directions for future research that could help shed light on the mechanisms that contribute to the belief that money carries traces of its moral history.

This chapter examines associationist models of cognitive development, focusing on the development of naming in young children — the process by which young children learn of construct the meanings of words and concepts. It presents two early-emerging insights that children possess about the nature of naming. These insights are: essentialism: certain words map onto nonobvious, underlying causal features, and genericity: certain expressions map onto generic kinds as opposed to particular instances. The chapter discusses empirical studies with preschool children to support the contention that essentialism and genericity emerge early in development and that neither insight is directly taught. It also explores the question of whether these insights can be derived wholly from a direct reading of cues that are ‘out there’in the world, and concludes that they cannot. The implications of these findings for innateness are then considered. It is argued that both essentialism and genericity provide cues regarding plausible candidates for innate conceptual knowledge in children.

Generics (e.g., “Ravens are black”) express generalizations about categories or their members. Previous research found that generics about animals are interpreted as broadly true of members of a kind, yet also accepted based on minimal evidence. This asymmetry is important for suggesting a mechanism by which unfounded generalizations may flourish; yet, little is known whether this finding extends to generics about groups of people (heretofore, “social generics”). Accordingly, in four preregistered studies (n = 665), we tested for an inferential asymmetry for generics regarding novel groups of animals versus people. Participants were randomly assigned to either an Implied Prevalence task (given a generic, asked to estimate the prevalence of a property) or a Truth-Conditions task (given prevalence information, asked whether a generic was true or false). A generic asymmetry was found in both domains, at equivalent levels. The asymmetry also extended to properties varying in valence (dangerous and neutral). Finally, there were differences as a function of property valence in the Implied Prevalence task and a small but consistent interaction between domain and prevalence in the Truth-Conditions task. We discuss the implications of these results for the semantics of generics, theoretical accounts of the asymmetry, and the relation between generics and stereotyping.

The present study examined children's understanding of illness in a peri-urban community in South Africa where AIDS is prevalent. Results suggest that children were surprisingly knowledgeable about AIDS at an early age, and may have even erroneously analogized from AIDS to the flu. Furthermore, all age groups attributed different causes for AIDS and flu. However, although factual knowledge about AIDS was identified among all age groups, there was no evidence of understanding biological causal mechanisms. The data have implications both for developmental research on biological reasoning in diverse cultural contexts and for the design of health education programs.