Janellen Huttenlocher

Early Vocabulary Growth: Relation to Language Input and Gender.

This study examines the role of exposure to speech in childrens early vocabulary growth. It is generally assumed that individual differences in vocabulary depend, in large part, on variations in learning capacity. However, variations in exposure have not been systematically explored. In this study we characterize vocabulary growth rates for each of 22 children by using data obtained at several time points from 14 to 26 months. We find a substantial relation between individual differences in vocabulary acquisition and variations in the amount that particular mothers speak to their children. The relation between amount of parent speech and vocabulary growth, we argue, reflects parent effects on the child, rather than child-ability effects on the parent or hereditary factors. We also find that gender is an important factor in rate of vocabulary growth. Early childhood is a period of rapid linguistic development. By 2 years, the average child acquires 900 root words (cf. Carey, 1978) and at least a rudimentary syntax (cf. Brown, 1973). Although there has been considerable recent interest in syntactic development, much less attention has been devoted to lexical development. Yet in tracing the development of language from its inception, lexical development must necessarily be a focus of study because the acquisition of words constitutes the childs initial achievement as a language user. A certain amount of vocabulary must be acquired before words can be combined into sentences, and, indeed, several months elapse between the time children start to produce words and the time they start to produce multiword utterances. In addition, vocabulary and syntax are not independent aspects of language knowledge; for example, verbs frequently encode actions involving relations among entities (e.g., give, feed) which are specified by the verb together with its arguments. A major concern in the recent work on syntactic development has been with the relative contributions of the childs innate preparedness for language versus language input. Yet the rapid growth of vocabulary in early childhood also is a manifestation of the human preparedness for language, and parallel questions arise concerning the relative contributions of capacity and input. Especially at the start of language learning, innate preparedness surely plays a role in acquiring word meanings because inferences about meanings are based on pairings of words with situations. As Quine (1969) has persuasively argued, the variety of aspects of a situation which might be encoded by a word is enormous. Because of this, Gleitman and Wanner (1982) point out, it seemscritical to posit innately available constraints on the possible meanings children entertain.

Categories and Particulars: Prototype Effects in Estimating Spatial Location.

A model of category effects on reports from memory is presented. The model holds that stimuli are represented at 2 levels of detail: a fine-grain value and a category. When memory is inexact but people must report an exact value, they use estimation processes that combine the remembered stimulus value with category information. The proposed estimation processes include truncation at category boundaries and weighting with a central (prototypic) category value. These processes introduce bias in reporting even when memory is unbiased, but nevertheless may improve overall accuracy (by decreasing the variability of reports). Four experiments are presented in which people report the location of a dot in a circle. Subjects spontaneously impose horizontal and vertical boundaries that divide the circle into quadrants. They misplace dots toward a central (prototypic) location in each quadrant, as predicted by the model. The proposed model has broad implications; notably, it has the potential to explain biases of the sort described in psychophysics (contraction bias and the bias captured by Webers law) as well as symmetries in similarity judgments, without positing distorted representations of physical scales.

Sources of Variability in Children’s Language Growth

The present longitudinal study examines the role of caregiver speech in language development, especially syntactic development, using 47 parent-child pairs of diverse SES background from 14 to 46 months. We assess the diversity (variety) of words and syntactic structures produced by caregivers and children. We use lagged correlations to examine language growth and its relation to caregiver speech. Results show substantial individual differences among children, and indicate that diversity of earlier caregiver speech significantly predicts corresponding diversity in later child speech. For vocabulary, earlier child speech also predicts later caregiver speech, suggesting mutual influence. However, for syntax, earlier child speech does not significantly predict later caregiver speech, suggesting a causal flow from caregiver to child. Finally, demographic factors, notably SES, are related to language growth, and are, at least partially, mediated by differences in caregiver speech, showing the pervasive influence of caregiver speech on language growth.

Why do categories affect stimulus judgment

The authors tested a model of category effects on stimulus judgment. The model holds that the goal of stimulus judgment is to achieve high accuracy. For this reason, people place inexactly represented stimuli in the context of prior information, captured in categories, combining inexact fine-grain stimulus values with prior (category) information. This process can be likened to a Bayesian statistical procedure designed to maximize the average accuracy of estimation. If people follow the proposed procedure to maximize accuracy, their estimates should be affected by the distribution of instances in a category. In the present experiments, participants reproduced one-dimensional stimuli. Different prior distributions were presented. The experiments verified that peoples stimulus estimates are affected by variations in a prior distribution in such a manner as to increase the accuracy of their stimulus reproductions.

The Coding of Spatial Location in Young Children.

The present paper is concerned with the representation of spatial location in young children. We report six experiments which indicate that the basic framework for coding location is present early in life. Later development consists of an increasing ability to impose organization on a broad range of bounded spaces. In the first four experiments, we examined whether very young children, like adults, can locate objects in a homogeneous space, estimating by eye the location of those objects within some frame of reference. Results show that children from 16 to 24 months are able to use distance to code the location of an object hidden in a large sandbox. Coding of distance is not dependent on a juxtaposed outside landmark, nor on the childs own position. In the last two experiments, we examine whether young children, like adults, code the location of an object hierarchically--not only as being in a particular location in a bounded space, but also as being within a larger segment of that space. The pattern of bias in responding provides evidence for such two-level coding of location. The age at which children impose subdivisions on a space depends on the nature of that space. The sandbox is subdivided by 10-year-olds, but not by 4- or 6-year-olds. In contrast, a rectangle of similar shape drawn on paper is subdivided even by 4-year-olds. We argue that 16-month-olds in the sandbox studies also use hierarchical coding, treating the whole box as a category, although they do not divide it into subsections.

Bayesian integration of spatial information.

Spatial judgments and actions are often based on multiple cues. The authors review a multitude of phenomena on the integration of spatial cues in diverse species to consider how nearly optimally animals combine the cues. Under the banner of Bayesian perception, cues are sometimes combined and weighted in a near optimal fashion. In other instances when cues are combined, how optimal the integration is might be unclear. Only 1 cue may be relied on, or cues may seem to compete with one another. The authors attempt to bring some order to the diversity by taking into account the subjective discrepancy in the dictates of multiple cues. When cues are too discrepant, it may be best to rely on 1 cue source. When cues are not too discrepant, it may be advantageous to combine cues. Such a dual principle provides an extended Bayesian framework for understanding the functional reasons for the integration of spatial cues.

Multiple cues for quantification in infancy: Is number one of them?

A review and synthesis of the literature on quantification in infancy and early childhood is provided. In most current conceptualizations, early quantification is assumed to be number based. However, the extant literature provides no clear-cut evidence that infants use number to perform quantitative tasks. Instead, new research suggests that quantification is initially based on nonnumerical cues, such as area and contour length, whether or not a task involves discrete items. The authors discuss the implications of these findings with respect to early quantification and its relation to later numerical development.

Mental rotation and the perspective problem

Abstract Experiment I contrasts the difficulty of problems in which a child must anticipate the appearance of an array of objects that is rotated (rotation problems) to the difficulty of problems in which a child must anticipate the appearance of a fixed array to an observer who has been rotated with respect to it (perspective problems). Perspective problems are much more difficult and show a different error pattern. Experiment II contrasts standard perspective problems, in which a child must anticipate the appearance of the array to an observer whose position differs from his own, to “perspective-move” problems, in which a child must anticipate the appearance of the array from his own new position; i.e., he himself moves. The latter problems are much easier, and the error pattern is much like that for rotation problems. The mental operations involved in solving these various types of problems are discussed.

Quantitative development in infancy and early childhood

1. Historical Trends and Current Issues 2. Quantification in Infancy 3. Quantification in Early Childhood 4. Quantification of Discrete Sets: A Synthesis 5. Continuous Amount 6. Relative Quantity 7. Nonverbal Representation of Quantity 8. Acquiring Conventional Skills 9. The Whole Child

A mental model for early arithmetic.

The authors examined young childrens ability to solve nonverbal calculation problems in which they must determine how many items are in a hidden array after items have been added into or taken away from it. Earlier work showed that an ability to reliably solve such problems emerges earlier than verbal calculation ability but did not examine when it first appears. The authors propose that the ability to solve such problems involves domain-general symbolic processes similar to those involved in symbolic play and the use of physical models. Hence the ability to calculate should appear at about 2 years and should be related to overall level of intellectual competence. The authors show that the ability to reliably solve nonverbal calculation tasks emerges only after 2 years of age and that performance on nonverbal calculation problems is highly related to overall level of intellectual competence in children between 3 and 4 years of age.