Psychological Essentialism in Children (2004) PDF

Review TRENDS in Cognitive Sciences Vol.8 No.9 September 2004 Language and Conceptual Development series Psychological essentialism in children Susan A. Gelman University of Michigan, Ann Arbor, MI 48109-1109, USA Psychological essentialism is the idea that cert...

Review TRENDS in Cognitive Sciences Vol.8 No.9 September 2004 Language and Conceptual Development series Psychological essentialism in children Susan A. Gelman University of Michigan, Ann Arbor, MI 48109-1109, USA Psychological essentialism is the idea that certain Evidence for psychological essentialism categories, such as ‘lion’ or ‘female’, have an underlying Fodor argued that essentialism is the outgrowth of reality that cannot be observed directly. Where does this modern scientific and technological knowledge, with its idea come from? This article reviews recent evidence corresponding focus on non-obvious constructs such as suggesting that psychological essentialism is an early genes and chromosomes. Children provide a critical cognitive bias. Young children look beyond the obvious test case of this idea precisely because they lack detailed in many converging ways: when learning words, scientific knowledge. If essentialism requires knowledge generalizing knowledge to new category members, of modern science and technology then it should emerge reasoning about the insides of things, contemplating relatively late in development. By contrast, if essentialism the role of nature versus nurture, and constructing can be found in preschool children then this would imply causal explanations. These findings argue against the that the doctrine is likely to have a more fundamental standard view of children as concrete thinkers, instead basis. claiming that children have an early tendency to search What would be evidence for essentialism, in children or for hidden, non-obvious features. adults? Medin and Ortony suggest that essentialism is a ‘placeholder’ notion: one can believe that a category possesses an essence without knowing what the essence Why do preschool children often insist that mothers can’t is. For example, a child might believe that there exist be firefighters? Why do adults who were adopted in deep, non-visible differences between males and females, infancy sometimes search for their birth parents? Why but have no idea just what those differences are. The do art collectors pay more money for an original painting essence placeholder would imply that categories permit than for an exact copy? These examples, although widely rich inductive inferences, capture underlying structure (in varying in content, can be understood within a framework the form of causal and other non-obvious properties), have of psychological essentialism. innate potential, and have sharp and immutable bound- Essentialism is the view that certain categories have an aries. I have detailed at length elsewhere the evidence underlying reality or true nature that one cannot observe that preschool children expect certain categories to have directly but that gives an object its identity, and is all of these properties. It is beyond the scope of this responsible for other similarities that category members article to review the full range of evidence here. However, share [1,2]. In the domain of biology, an essence would be I briefly summarize below some of the major findings. whatever quality remains unchanging as an organism grows, reproduces, and undergoes morphological trans- formations (baby to man; caterpillar to butterfly). In the Inductive potential domain of chemistry, an essence would be whatever Induction is the capacity to extend knowledge to novel quality remains unchanging as a substance changes instances, for example, inferring that a newly encountered shape, size, or state (from solid to liquid to gas). mushroom is poisonous on the basis of past encounters Essentialist accounts have been proposed and dis- with other poisonous mushrooms. This capacity is one of cussed for thousands of years, extending back at least to the most important functions of categories. Categories Plato’s cave allegory in The Republic. Numerous fields, serve not only to organize the knowledge we have already including biology, philosophy, linguistics, literary critic- acquired but also to guide our expectations. Young ism, and psychology, stake claims about essentialism. children’s category-based inferences are consistent with Here we are concerned with essentialism as a psycho- essentialism in two respects. First, children readily infer logical claim (see Box 1). Although there are serious properties that concern internal features and non-visible problems with essentialism as a metaphysical doctrine, functions from one category member to another. Second, recent psychological studies converge to suggest that children draw inferences even when category membership essentialism is a reasoning heuristic that is readily competes with perceptual similarity. available to both children and adults. This article Figure 1 provides an example from a set of studies reviews such evidence, and discusses the implications for conducted some years ago by Gelman and Markman [6,7]. The leaf (Figure 1a) and the leaf-insect (Figure 1c) have human concepts. overall similarity: both are large and green, with striped Corresponding author: Susan A. Gelman ([email protected]). markings, and share overall shape. However, if told the Available online 29 July 2004 category membership of each of the three items – (a) ‘leaf ’, www.sciencedirect.com 1364-6613/$ - see front matter Q 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.tics.2004.07.001  Review TRENDS in Cognitive Sciences Vol.8 No.9 September 2004 405 Box 1. Defining essentialism The words ‘essence’ and ‘essentialism’ are used loosely by a range of relationship, or entity that causes other category-typical properties scholars to mean a wide range of things. Three factors jointly serve to to emerge and be sustained, and that confers identity. For example, map out the various types of essentialism. the causal essence of tigers might be something like tiger DNA, which is responsible for various observable properties that tigers have. The Where is the essence located? cluster of properties ‘striped, ferocious, and large’ is not a causal Is it in the world (metaphysical essentialism) or in human represen- essence of tigers, despite being true of all (or most) members of the tations (representational essentialism)? The former is a philosophical category, because the properties lack causal force. position concerning objective reality; the latter addresses how people The ideal essence is assumed to have no actual instantiation in the construe reality (in their belief systems, language, and cultural world. For example, on this view the essence of ‘goodness’ is some practices). Essentialism faces difficulties as a characterization of the pure quality that is imperfectly realized in real-world instances of natural world. Social categories, such as race and caste, have no people performing good deeds. Plato’s cave allegory, in which what true underlying essence [17,21]. Biological species also are without an we see of the world are mere shadows of what is real and true, essence because they evolve and are population-based rather than exemplifies this view. The ideal essence contrasts with both the sortal reflecting properties inherent in each individual [44,45]. Furthermore, and the causal essences, which concern qualities of real-world whereas essentialism implies that there is a single appropriate entities. classification for each organism, there might in fact be numerous valid classifications. The essentialist view therefore seems to be a What degree of specificity is entailed? human construction rather than a perceived reality. Are essences specific (their particulars known and identified) or placeholder (their particulars unknown and perhaps unknowable)? What is the ontological type of an essence? Specific essentialism posits that a category essence is known and Is it sortal (serving to define categories), causal (having consequences contributes to the meaning and use of a category label (e.g. H2O for for category structure), or ideal (having no real-world instantiation)? water), whereas placeholder essentialism suggests that a person The sortal essence is the set of defining characteristics that all and believes that there is some causal essence that holds a category only members of a category share. On this view the essence of a together, without knowing just what that essence is (e.g. that all grandmother would be the property of being the mother of a person’s samples of water share some inherent, non-obvious property). parent (rather than accidental properties such as having gray hair). Although placeholder essentialism would typically be insufficient to The viability of this account has been called into question by models of determine word extensions, it has implications for people’s beliefs concepts that stress the importance of probabilistic features, exem- regarding the depth and stability of a concept. plars, and theories in concepts. In this article, the focus is on representational, causal, placeholder The causal essence is the substance, power, quality, process, essentialism. (b) ‘bug’, (c) ‘bug’ – and asked to draw novel inferences uniformly with all labels. The explanation that accounts about the leaf-insect, children rely on the category most satisfactorily for the varied patterns of data is that membership conveyed by the label. Once children learn children assess the extent to which entities are members a new fact about one member of a category, they generalize of the same category (often conveyed via a label or phrase, the fact to other members of that category, even if the two although not necessarily), and independently assess the category members look substantially different. This effect extent to which the property in question is a relatively holds up for animals (bird, fish, rabbit), for natural enduring (versus temporary or accidental) feature (but see substances (gold, cotton), and for social categories (boy, for debate). Category-based induction results only girl, smart, shy) [8,9]. It is found when using three- when the entities belong to a category and the property is dimensional objects as well as drawings. The effect is relatively enduring. When other causal mechanisms are found with adults as well as children [6,11]. Even 1- and known and available, however, category-based induction 2-year-old children draw category-based inferences about seems to be less frequent. atypical instances [12,13]. Thus, the appreciation that words can signal non-obvious properties seems in place at Innate potential the very start of word learning. One of the most important kinds of evidence for essen- By 4 years of age, children display subtlety and tialism is the belief that properties are fixed at birth, that flexibility regarding when they do and don’t make is, that an organism displays innate potential. Details category-based inductive inferences. They do not use vary, but the basic paradigm to test this notion is as a simple matching strategy, in which they extend proper- follows: children learn about a person or animal that has ties only when two items share identical labels. The effect a set of biological parents, but is switched at birth to a emerges not only with familiar labels, although not new environment and a new set of parents. Children are then asked to decide whether the birth parents or the (a) (b) (c) upbringing parents determine various properties. For example, in one item set, children learned about a newborn kangaroo that went to live with goats, and were asked whether it would be good at hopping or good at climbing, and whether it would have a pouch or no pouch Figure 1. Sample item set used in studies with preschool children [6,7]. The item. Preschool children typically reported that it would be sets were constructed so that overall similarity (in shape and color) was pitted good at hopping and have a pouch. Even if it cannot hop at against shared category membership. This set comprised (a) a leaf, (b) a beetle, and birth (because it is too small and weak), and is raised by (c) a leaf-insect. When 3- and 4-year-old children heard labels for these items (‘leaf’, ‘bug’, and ‘bug’, respectively), they were more likely to extend new information on goats that cannot hop, and never sees another kangaroo, the basis of shared label than on the basis of overall similarity. hopping is inherent to kangaroos. Therefore this property www.sciencedirect.com 406 Review TRENDS in Cognitive Sciences Vol.8 No.9 September 2004 will eventually be expressed. Although there is debate as children attribute actions and growth to an animal’s to when precisely this understanding emerges , on a ‘insides’. conservative estimate it appears by about 6 years of age, Children also privilege internal, non-obvious properties and in some studies as early as age 4 years. This is so when in their categories (see Figures 2 and 3). By 4 or 5 years of children reason about animal categories, plant categories, age, children often recognize that an animal cannot be and social categories [3,17,18]. Intriguingly, for some transformed into another kind of thing (for example, a categories children are more nativist than adults. For raccoon cannot become a skunk). Instead, category example, 5-year-olds predict that a child who is switched membership is stable over striking transformations [15,30]. at birth will speak the language of the birth parents rather Also, non-obvious properties, especially internal proper- than the adoptive parents. The degree to which a ties, appear to be salient to young children and are nativist bias is expressed varies across cultures, but privileged in their determinations of what things are. Torguud adults in Western Mongolia , adults in This finding appears not only among middle-class children India , Vezo children in Madagascar , and Itzaj in the US, but also in middle-class and Favela-dwelling Maya adults and children in Mexico all display a children in Brazil. nativist bias. Summary Underlying structure The studies reviewed here suggest that both preschool Underlying structure can be seen in the importance children and adults from a variety of cultural contexts children grant to causality, and to non-obvious features. expect members of a category to be alike in non-obvious By 2 years of age children view causes as vital to what ways. They treat certain categories as having inductive something is. Features that are causes are more core than potential, an innate basis, stable category membership, non-causal features. Causes are more important than and sharp boundaries between contrasting categories. mere associations; causes are also more important than These beliefs are not the result of a detailed knowledge effects. Furthermore, features that are causally base, nor are they imparted directly by parents , coherent (meaning that they fit together in an explanatory although language might play an important indirect role framework) are weighted more heavily than features (see Box 2). Instead, they appear early in childhood with that are equally available but not participating in a relatively little direct prompting. network of causal explanations. Recent work with adults details more formally the importance of causality in What psychological essentialism implies about children adults’ concepts [26,27]. Childhood essentialism poses a challenge to more tradi- Causality is further central to children’s categories in tional theories of children’s concepts, which have empha- that children provide consistent, domain-specific causal sized their focus on superficial, accidental, or perceptual explanations for the properties that members of a category share. Even 3-year-olds attribute an animal’s actions to the animal itself, rather than to an external force (inherent cause). By 4 years of age, children appeal to ‘energy’ as a causal force [3,29]. By 8 years of age, Figure 2. Sample item used to study what procedures children deem relevant when determining ambiguous category membership (Lizotte and Gelman, reported in ). Five-year-olds and college students saw a series of trials depicting a pair of Figure 3. Sample items used in a study examining the role of internal parts in items that looked nearly identical. They were told that the two items differed in directing children’s word learning. (The original items were in color.) some respect (e.g. one was a dog and one was a wolf; or one was an animal and one (a) Brazilian and US 4-year-old children learned a new word referring to a novel was a toy), and that their job was to figure out which item was which. They were sub-type of a familiar category; for example, ‘zava’ for the snake in the bottom panel asked to decide (yes/no answers) whether checking any of the following would be of (a), and were then asked to find the snake(s) and the zava(s) from among the informative procedures: insides, origins/parentage, behaviors, or age. The results three pictures in (b). Children who heard that the two animals in (a) shared internal indicated that children and adults believe that the items can be distinguished by a similarities (e.g. have the same kind of bones, blood, muscles and brain) were more wide range of means: not just by external behaviors but also by internal properties likely to learn the new word correctly (as a sub-type of snake) than children in a and origins. Five-year-olds and adults reported that origins and insides are control condition who heard that the two animals shared superficial similarities important clues as to which of two seemingly identical animals is a dog or a (e.g. are the same size, and live in the same zoo in the same kind of cage). Children wolf, although it is unlikely that they could say specifically how the insides of dogs in the control condition were instead more likely to interpret the two labels and wolves differ. (e.g. snake and zava) as mutually exclusive. Reproduced with permission from. www.sciencedirect.com  Review TRENDS in Cognitive Sciences Vol.8 No.9 September 2004 407 Box 2. Language and essentialism The language that is used to express membership in a category adverse environmental conditions. (For other examples of noun- can influence children’s judgments about that category. Count labeling effects, see also [12,13,48–50].) nouns imply that a category is relatively more stable and Generic noun phrases express essential qualities and imply that a consistent over time and contexts than adjectives or verbal category is coherent and permits category-wide inferences. When phrases. For example, in one study , 5- and 7-year-old children 4-year-old children hear a new fact in generic form (e.g. ‘Bears have first learned about a set of individuals with either a count noun three layers of fur’), they treat this fact as typically true of most or all (‘Rose is 8 years old. Rose eats a lot of carrots. She is a carrot- category members. Generic nouns are plentiful in the speech that eater.’) or a verbal phrase (‘Rose is 8 years old. Rose eats a lot of children hear [32,53], and children are highly sensitive to cues that carrots. She eats carrots whenever she can.’). They were then mark genericity [54–56]. probed for how stable they thought this category membership Additionally, there are language-specific devices that convey would be across time and different environmental conditions essentialism. For example, young Spanish-speaking children make (e.g. ‘Will Rose eat a lot of carrots when she is grown up?’ ‘Would inferences about the stability of a category based on which form of the Rose stop eating a lot of carrots if her family tried to stop her verb ‘to be’ is used to express it (ser versus estar; ). Although it is from eating carrots?’). Children who heard the count noun were unlikely that language is the source of psychological essentialism, it more likely than children who heard the verbal phrase to judge provides important cues to children regarding when to treat categories that the personal characteristics would be stable over time and as stable and having an intrinsic basis. features. At the extreme, Piaget and his colleagues theories of concepts have been based on considering which suggested that children are incapable of forming ‘true’ known properties are most privileged, and in what form. concepts. Likewise, many scholars have proposed one or By contrast, essentialism tells us that known properties do another developmental dichotomy: from concrete to not constitute the full meaning of concepts. Concepts are abstract, from surface to deep, from perceptual to concep- also open-ended. They are in part placeholders for tual. On the contrary, there are remarkable commonalities unknown properties. between the concepts of children and those of adults. Some Historically, it has often been assumed that there is a scholars still maintain that developmental dichotomies single, unitary process of categorization. Yet essen- might exist earlier in development (e.g. from 1–2 years, tialism makes clear that categorization cannot be said to instead of from 5–7 years , but see ). be a single thing. Categorization serves many different However, essentialism does not posit that perceptual functions, and we recruit different sorts of information features or similarity are unimportant to early concepts. depending on the task at hand. Rapid identification calls Even within an essentialist framework, appearances provide for one kind of process; reasoning about genealogy calls for crucial cues regarding an underlying essence. Similarity another. Task differences yield different categorization appears to play an important role in fostering comparisons processes. Even when the task is restricted to object between representations and hence discovery of new identification, people make use of different sorts of abstractions and regularities. Rather than suggesting information depending on the task instructions. Two that human concepts overlook perception or similarity, separate categorization procedures, rule application and essentialism carries with it the assumption that a category judging similarity to an exemplar, can readily apply to the has two distinct, although interrelated, levels: the level of same categories, although they activate different neural observable reality and the level of explanation and cause. regions in the adult brain. Domain is also an It is this two-tier structure that might serve to motivate important consideration. Although essence-like con- further development, leading children to develop more struals can be found in concepts of artwork and artifacts sophisticated understandings. Most developmental , essentialism is found most often with natural kinds accounts of cognitive change include something like this and certain social categories. Categories such as penguin structure, such as equilibration, competition, theory or apple tree imply inherent non-obvious properties, change, analogy, or cognitive variability (see for inductive potential, and innate commonalities not found review). In all these cases, as with essentialism, children with categories like window or crayon. consider contrasting representations. When new evidence Because essentialism is found early in childhood, all of conflicts with the child’s current understanding, this can the points discussed above must be operating in quite lead the child gradually to construct new representations. basic and fundamental ways. In other words, we cannot Indeed, targeted interventions that introduce a non- simply assume that these are frills added on top of basic or obvious similarity between dissimilar things can lead to standard categorization. dramatic change in children’s concepts. Perhaps not surprisingly, then, children look beyond observable fea- Conclusion tures when trying to understand the categories of their Recent work has shown that preschool children treat a world. In positing a reality beyond appearances, the variety of natural categories as having substantial search is on for more information, deeper causes, and inductive potential, innate properties, and underlying alternative construals. structure. Related to this, there are several important aspects to children’s concepts from very early in life, What psychological essentialism implies about including placeholder notions, theory-based properties, concepts category and task variability, and interdependence of There is an idealized model of categorization that has categorization and other cognitive processes. More gener- formed the basis for much work in psychology. Standard ally, these findings overturn assumptions about what is www.sciencedirect.com 408 Review TRENDS in Cognitive Sciences Vol.8 No.9 September 2004 Box 3. Alternative accounts Although the data reviewed in this article are consistent with incorporates the former and adds to it the idea that some part or psychological essentialism in children, they fall short of providing quality (i.e. the essence) causes the properties shared by the kind. In direct evidence. Children do not explicitly articulate an essentialist the literature, the two notions have often been treated as interchange- perspective, and the word ‘essence’ probably does not enter the able. However, categories can be bound together in crucial ways vocabulary until well into school-age years. Nor can we say with any without considering the causal basis of the kind. In an important precision what the essence of, say, a dog or a tree is to a child. argument, Strevens suggests that the data taken as evidence for Perhaps, then, essentialism is unnecessary, and we should instead psychological essentialism could instead be accounted for if people refer to the component phenomena discussed earlier (e.g. categories simply assume that there are causal laws connecting kind member- have inductive potential; causal features are central to categories). ship with observable properties. He terms such causal laws ‘K-laws’ One reason to frame these results in terms of essentialism is (kind laws), and his alternative formulation the ‘Minimal Hypothesis’. parsimony: a range of phenomena that co-occur within a relatively Strevens’s account, although eschewing essentialism, overlaps with brief developmental span seem to be instantiations of a single broader the current model in emphasizing that people treat surface features as principle. This argument, however, requires a closer empirical caused and constrained by deeper features of concepts. foundation. More fine-grained analysis will be needed to discover Developmentally, a notion of kind might precede a notion of essence. how tightly linked these various phenomena are, both in adult Evidence for use of kinds is present by age 2 years (in children’s cognition and in development (see for an excellent start). A inductive inferences), but evidence for appeal to an essence (e.g. with second consideration is the existence of explicit essence formulations the switched-at-birth method) has so far not appeared below age 4 among adults in varied cultures. By treating people’s implicit years. An important direction for future research would be to use construals as essentialist, a common framework covers both the converging methods to try to distinguish ‘kind’ from ‘essence’ at explicit and the implicit phenomena. different points in development. Nonetheless, something more than Even if essentialist phenomena can reasonably be considered the Minimal Hypothesis might be required to account for essentialist- interrelated, this does not mean that the concept is indivisible. Indeed, like behavior in children aged 4 years and over. psychological essentialism appears to have two related although There are additional issues that are beyond the scope of this article separable assumptions: (a) a kind assumption, that people treat but nonetheless important to mention. Some scholars have argued certain categories as richly structured ‘kinds’ with clusters of that essentialism cannot account for a variety of experimental findings correlated properties; and (b) an essence assumption, that people with adults [61–64]. For example, the extent to which different liquids believe a category has an underlying property (essence) that cannot be are judged to be water is independent of the extent to which they share observed directly but that causes the observable qualities that the purported essence of water, H2O. Whether these findings under- category members share. mine (or even conflict with) psychological essentialism is a matter of The major difference between kind and essence is that the latter current debate [3,39]. Box 4. Questions for future research † How coherent are essentialist beliefs? Do different strands † How does essentialism change with the acquisition of more (e.g. nativism, inductive potential, boundary intensification) all detailed scientific knowledge? Does essentialism disappear with the ‘hang together’, or do they develop piecemeal? Is there a single acquisition of a scientific theory, or do the two frameworks co-exist in essentialist ‘stance’ , or is it the amalgamation of a variety of other adult reasoning? Lay adults’ conceptual difficulties with evolutionary tendencies ? theory and genetics argue against true conceptual reorganization. † Why do children (and adults) essentialize? Some existing † Can certain inputs reduce children’s reliance on essentialism? If proposals include the following: an innate, domain-specific module so, of what sort? for reasoning about biological species ; a domain-general † Are there stable individual differences in essentialism, and if so, consequence of sortals and count nouns ; the convergence of a what is the source of such differences [67,68]? Are individual variety of other early-emerging capacities needed for conceptual differences in essentialism related to individual differences in stereo- growth in childhood. typing? How does essentialism differ from other related notions, † We know that non-verbal and preverbal organisms categorize , including stereotyping and entitativity ? but do non-verbal and preverbal organisms also treat categories as † Is essentialism found in the same way and to the same extent having a non-obvious basis? If so, how could we tell? If not, why not? across cultures, or is there systematic variation ? simple or basic in human concepts. I have provided a 2 Medin, D.L. and Ortony, A. (1989) Psychological essentialism. In framework of ‘psychological essentialism’ to account for Similarity and Analogical Reasoning (Vosniadou, S. and Ortony, A. eds), pp. 179–195, Cambridge University Press these data (although see Box 3 for alternative accounts 3 Gelman, S.A. (2003) The Essential Child: Origins of Essentialism in and debates). Ongoing research examines developmental Everyday Thought, Oxford University Press antecedents in infancy, how best to understand the 4 Fodor, J. 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