A central form of human knowledge is generic knowledge, that is, general information about categories, from animals to numbers, from celestial objects to machines, from economic systems to social systems. Human progress is marked by a search for understanding principles that apply broadly across varying instances within a category. A fundamental means of expressing general knowledge to children is via language, and in particular generic noun phrases (e.g., "Insects are 6-legged"). Prior work has demonstrated that generic noun phrases are frequent in parental speech to children, used in diverse cultural and linguistic contexts (U.S., China, Peru), produced by children exposed to minimal linguistic input (deaf children not exposed to sign language), understood appropriately by preschool-aged children, and stored by children in long-term memory. These component pieces all suggest that generics are important, meaningful, acquired early, and have the potential to influence children's world knowledge. However, prior work on generics leaves two major questions unanswered: (1) Does generic language affect and guide children's concepts, or does generic language merely reflect children's concepts? (2) What is the process by which generic language is acquired in childhood? The project will investigate both these core issues. An in-depth training study will teach young children a new concept under varied wording conditions to chart the effects of generics and labeling on children's categorical reasoning. Furthermore, a set of experiments will test competing claims regarding the process by which generics are learned. These studies will make use of experimental research and naturalistic language analyses to provide converging and precise evidence regarding the links among concepts and language in children between 2 and 5 years of age.
The project will promote more effective learning strategies by providing much-needed information on how the language that parents and teachers use (generic vs. specific) affects how children acquire and generalize new information. These findings will help us understand better how children learn language, and have implications for science education. Furthermore, understanding how and when children form generalizations within categories informs the development of stereotyping, as well as how children come to understand human diversity. Finally, the work will benefit society at large, by providing scientists, educators, and parents with an understanding of children's early cognitive processes and the effects of language on such processes. Understanding how these basic processes unfold in normally developing children also provides a framework for eventually understanding how they can go awry, for example, in children with specific language impairment.
An important discovery of the past 20 years is that young children are impressive learners and understand the world in surprisingly sophisticated ways. One example of this advanced capacity can be found in how children organize their experience into categories. When children form everyday categories, such as dogs, birds, boys, or girls, they are not simply attending to superficial features such as color, shape, size, or hair length. Instead, young children believe that for certain categories, outward appearances are less important than non-obvious, internal properties. For example, preschoolers believe that even very dissimilar members of a category (e.g., crows and flamingos) have the same behaviors and the same kinds of internal parts. They also believe that many important features are inborn and can’t be changed (e.g., reporting that a boy raised in an all-female environment will nonetheless prefer football to ballet). These beliefs are sometimes referred to as "psychological essentialism", and characterize many of the categories formed by adults as well as children. One goal of this research project was to examine whether the way parents speak to children might transmit essentialist views. To examine this question, we invited parent-child pairs to read a picture book that we prepared about an unfamiliar, invented animal. Parents read the book at home repeatedly over 1-2 weeks. For some families, the books were written so that every page referred to the entire category ("Zarpies chase shadows"). For other families, the books were written so that every page referred to a specific instance ("This zarpie chases shadows"). Yet another set of families heard no labels whatsoever ("This chases shadows"). We then gave the participating parents and children a series of tasks aimed to examine how they reason about zarpies. For example, participants might learn a new fact about one zarpie, and be asked whether it generalizes to other zarpies. We found that children and parents reasoned quite differently about zarpies, depending on the language they had heard during the book-reading. For example, those who learned about zarpies as an entire category made more generalizations about new facts, treated zarpies as more stable over time, and even gave different explanations for why an animal had certain features. These results demonstrate that the language we provide when talking to young children has powerful effects on how they reason about the world. Moreover, these same effects took place for parents as they read to and taught their children. In follow-up work, we have also been studying how essentialist beliefs lead children to make errors when reasoning about scientific concepts. A second goal of this research project was to examine how children come to understand general statements such as "Zarpies chase shadows", "Dogs are 4-legged", or "Birds lay eggs". These expressions (which linguists call "generic" sentences) pose many challenges for child learners. First, they are abstract in meaning: you can’t point to dogs in general, the way you might point to any particular dog. Second, even though they are general statements, they also allow for exceptions. For example, although only female birds lay eggs, we generalize this fact to birds as a category. Third, linguistic cues are inconsistent and ambiguous. For example, "A bird has feathers" and "Birds have feathers" both refer to general categories, but "A bird flew past my window" and "Birds are nesting in that tree" refer to particular individuals, not general categories. Using a variety of experimental methods, we have discovered that young children interpret generic sentences in remarkably similar ways to adults, and that generic statements may even be a "default" interpretation for young children. Altogether, this research suggests that children possess early-developing ideas about categories that are supported and influenced by subtle cues in the language input that parents provide.
