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We review findings from a four-year longitudinal study of language learning conducted on two samples: a sample of typically developing children whose parents vary substantially in socioeconomic status, and a sample of children with pre- or perinatal brain injury. This design enables us to study language development across a wide range of language learning environments and a wide range of language learners. We videotaped samples of children's and parents' speech and gestures during spontaneous interactions at home every four months, and then we transcribed and coded the tapes. We focused on two behaviors known to vary across individuals and environments-child gesture and parent speech-behaviors that have the potential to index, and perhaps even play a role in creating, differences across children in linguistic and other cognitive skills. Our observations have led to four hypotheses that have promise for the development of diagnostic tools and interventions to enhance language and cognitive development and brain plasticity after neonatal injury. One kind of hypothesis involves tools that could identify children who may be at risk for later language deficits. The other involves interventions that have the potential to promote language development. We present our four hypotheses as a summary of the findings from our study because there is scientific evidence behind them and because this evidence has the potential to be put to practical use in improving education.

Understanding measurement units is critical to mathematics and science learning, but it is a topic that American students find difficult. In 3 studies, we investigated the challenges underlying this difficulty in kindergarten and second grade by comparing performance on different versions of a linear measurement task. Children measured crayons that were either aligned or shifted relative to the left edge of either a continuous ruler or a row of discrete units. The alignment (aligned, shifted) and the measuring tool (ruler, discrete units) were crossed to form 4 types of problems. Study 1 showed good performance in both grades on both types of aligned problems as well as on the shifted problems with discrete units. In contrast, performance was at chance on the shifted ruler problems. Study 2 showed that performance on shifted discrete unit problems declined when numbers were placed on the units, particularly for kindergarteners, suggesting that on the shifted ruler problems, the presence of numbers may have contributed to children's difficulty. However, Study 3 showed that the difficulty on the shifted ruler problems persisted even when the numbers were removed from the ruler. Taken together, these findings suggest that there are multiple challenges to understanding measurement, but that a key challenge is conceptualizing the ruler as a set of countable spatial interval units.

Previous studies of children's reorientation have focused on cue representation (e.g., whether cues are geometric) as a predictor of performance but have not addressed cue reliability (the regularity of the relation between a given cue and an outcome) as a predictor of performance. Here we address both factors within the same series of experiments. We show that for 18- to 30-month-olds, high cue reliability is a dominant factor positively affecting reorientation behavior. Under conditions of high cue reliability, children use both scalar and nonscalar cues for successful reorientation. By contrast, under conditions of low cue reliability, children successfully use scalar cues but not nonscalar cues, suggesting that mapping of left-right visual features onto a viewer-centric sense of left and right is facilitated when features themselves are ordered. More generally, we suggest that cue-driven spatial reorientation is best understood as part of a broader system capable of flexibly linking stimuli and responses.

When geometric and non-geometric information are both available for specifying location, men have been shown to rely more heavily on geometry compared to women. To shed insight on the nature and developmental origins of this sex difference, we examined how 18- to 24-month-olds represented the geometry of a surrounding (rectangular) space when direct non-geometric information (i.e. a beacon) was also available for localizing a hidden object. Children were tested on a disorientation task with multiple phases. Across experiments, boys relied more heavily than girls on geometry to guide localization, as indicated by their errors during the initial phase of the task, and by their search choices following transformations that left only geometry available, or that, under limited conditions, created a conflict between beacon and geometry. Analyses of search times suggested that girls, like boys, had encoded geometry, and testing in a square space ruled out explanations concerned with motivational and methodological variables. Taken together, the findings provide evidence for an early sex difference in the weighting of geometry. This sex difference, we suggest, reflects subtle variation in how boys and girls approach the problem of combining multiple sources of location information.

In this paper we examine the relations between parent spatial language input, children's own production of spatial language, and children's later spatial abilities. Using a longitudinal study design, we coded the use of spatial language (i.e. words describing the spatial features and properties of objects; e.g. big, tall, circle, curvy, edge) from child age 14 to 46 months in a diverse sample of 52 parent-child dyads interacting in their home settings. These same children were given three non-verbal spatial tasks, items from a Spatial Transformation task (Levine et al., 1999), the Block Design subtest from the WPPSI-III (Wechsler, 2002), and items on the Spatial Analogies subtest from Primary Test of Cognitive Skills (Huttenlocher & Levine, 1990) at 54 months of age. We find that parents vary widely in the amount of spatial language they use with their children during everyday interactions. This variability in spatial language input, in turn, predicts the amount of spatial language children produce, controlling for overall parent language input. Furthermore, children who produce more spatial language are more likely to perform better on spatial problem solving tasks at a later age.

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. (Contains 6 figures and 9 tables.)

Prior studies indicate that children vary widely in their mathematical knowledge by the time they enter preschool and that this variation predicts levels of achievement in elementary school. In a longitudinal study of a diverse sample of 44 preschool children, we examined the extent to which their understanding of the cardinal meanings of the number words (e.g., knowing that the word "four" refers to sets with 4 items) is predicted by the "number talk" they hear from their primary caregiver in the early home environment. Results from 5 visits showed substantial variation in parents' number talk to children between the ages of 14 and 30 months. Moreover, this variation predicted children's knowledge of the cardinal meanings of number words at 46 months, even when socioeconomic status and other measures of parent and child talk were controlled. These findings suggest that encouraging parents to talk about number with their toddlers, and providing them with effective ways to do so, may positively impact children's school achievement. (Contains 2 footnotes, 4 tables, and 5 figures.)

It has been suggested that young children can only reorient, locating a target object, when the geometry of an enclosed space provides distinctive shape information [e.g., Hermer, L., & Spelke, E. (1994). A geometric process for spatial reorientation in young children. "Nature," 370, 57-59]. Recently, however, young children were shown to specify location in a square-shaped space, where geometry is uninformative, so long as scale-like information was available on the walls of the space [Huttenlocher, J., & Lourenco, S. F. (2007a). Coding location in enclosed spaces: Is geometry the principle? "Developmental Science," 10, 741-746]. Here we build on this work by examining more closely what types of cues afford 18- to 24-month-olds an advantage in locating a target object following disorientation. Their performance was assessed when linear scale-like information was presented either in isolation or in composite form. It was found that, even in isolation, young children searched at the appropriate locations, with added benefit when presented as a composite. We suggest that linear scale-like dimensions, especially when available in composite form, play a critical role in supporting location representation in young children. (Contains 3 figures.)

The ability to locate objects in the environment is adaptively important for mobile organisms. Research on location coding reveals that even toddlers have considerable spatial skill. Important information has been obtained using a disorientation task in which children watch a target object being hidden and are then blindfolded and rotated so they cannot track their changing relation to the target. Even toddlers under two years of age search successfully for the hidden object, which shows that they can use geometric features of the spatial environment to determine object location. It has been claimed that these results show innate geometric abilities, but there is evidence that these early spatial skills are not simply geometric. The article presents an overview of experimental findings that provide the basis for a different interpretation of spatial development.

Previous studies have found that children have difficulty solving proportional reasoning problems involving discrete units until 10 to 12 years of age, but can solve parallel problems involving continuous quantities by 6 years of age. The present studies examine where children go wrong in processing proportions that involve discrete quantities. A computerized proportional equivalence choice task was administered to kindergartners through 4th-graders in Study 1, and to 1st- and 3rd-graders in Study 2. Both studies involved 4 between-subjects conditions that were formed by pairing continuous and discrete target proportions with continuous and discrete choice alternatives. In Study 1, target and choice alternatives were presented simultaneously; in Study 2, target and choice alternatives were presented sequentially. In both studies, children performed significantly worse when both the target and choice alternatives were represented with discrete quantities than when either or both of the proportions involved continuous quantities. Taken together, these findings indicate that children go astray on proportional reasoning problems involving discrete units only when a numerical match is possible, suggesting that their difficulty is due to an overextension of numerical equivalence concepts to proportional equivalence problems. (Contains 2 figures, 4 tables, and 2 footnotes.)

There is evidence that, from an early age, humans are sensitive to spatial information such as simple landmarks and the size of objects. This study concerns the ability to represent a particular kind of spatial information, namely, the "geometry" of an enclosed layout--an ability present in older children, adults, and nonhuman animals (e.g., Cheng, 1986; Hermer & Spelke, 1996). Using a looking-time procedure, 4.5- to 6.5-month-olds were tested on whether they could distinguish among the corners of an isosceles triangle. On each trial, the target corner was marked by a red dot. The stimulus (triangle with dot) appeared from different orientations across trials, ensuring that only cues related to the triangle itself could be used to differentiate the corners. When orientations were highly variable, infants discriminated the unique corner (i.e., the corner with the smaller angle and two equal-length sides) from a nonunique corner; they could not discriminate between the two nonunique corners. With less variable orientations, however, infants did discriminate between the nonunique corners of the isosceles triangle. Implications for how infants represent geometric cues are discussed. (Contains 5 figures.)

The present research examines the ability of children as young as 4 years to use models in tasks that require scaling of distance along a single dimension. In Experiment 1, we found that tasks involving models are similar in difficulty to those involving maps that we studied earlier (Huttenlocher, J., Newcombe, N., & Vasilyeva, M. (1999). Spatial scaling in young children. "Psychological Science, 10," 393-398). In Experiment 2, we found that retrieval tasks, where children indicate the location of a hidden object in an actual space are substantially more difficult than placement tasks, where children put a visible object in a particular location in an actual space. We discuss possible implications of the differential difficulty of retrieval and placement tasks for the understanding of symbolic development.

This paper presents the results of a longitudinal examination of syntactic skills, starting at the age of emergence of simple sentences and continuing through the emergence of complex sentences. We ask whether there is systematic variability among children from different socioeconomic backgrounds in the early stages of sentence production. The results suggest a different answer for simple versus complex sentences. We found a striking similarity across SES groups on the measures tapping early mastery of basic syntactic rules of simple sentences. At the same time, there was a significant difference between SES groups in the mastery of complex sentence structures. This difference emerged at the earliest stages of production of multi-clause sentences and persisted throughout the period of observation. The implications of these findings for the understanding of mechanisms of syntactic development are discussed.

Parents' object labels can be distinguished by whether the child is already attending to the object (follow-in) or not (lead-in). Lead-in labels have been found to be associated with low vocabulary. The current study examines whether the relation between lead-in labels and child vocabulary is influenced by whether the child's attention is redirected. Eighteen mother-infant dyads were videotaped at 1 ; 2, 1 ; 6 and 1 ; 10. Results indicate that parents' use of successful lead-in labels is positively correlated with children's vocabulary, whereas use of unsuccessful labels is negatively correlated. Finally, use of gesture is associated with the redirective success of lead-in labels.

The current studies used a syntactic priming paradigm with 3- and 4-year-old children. In Experiment 1, children were asked to describe a series of drawings depicting transitive and dative relations to establish baseline production levels. In Experiment 2, an experimenter described a similar series of drawings using one of two syntactic forms (i.e., active/passive for transitive; double-object/prepositional for dative). Children were then asked to describe pictures identical to those shown in the corresponding baseline procedure. In both transitive and dative conditions, 4-year-old children were more likely to use a particular syntactic form if it had been used by the experimenter. Three-year-old children did not show priming effects, but their production of transitive sentences was higher following transitive primes than in Experiment 1. In Experiment 3, an additional group of 3-year-olds participated in a procedure in which they repeated the experimenter's sentences before describing the pictures. This procedure yielded significant priming effects for transitive and dative forms. These results indicate that very young children possess abstract syntactic representations, but that their access to these representations is sensitive to task demands.

Both animals and human toddlers can find an object in a rectangular enclosure after they have been disoriented. They use geometric cues (relative lengths of walls) to discriminate among different corners (e.g. long wall to the left, short to the right). It has been claimed that this ability is "modular", i.e. exclusively geometric. The present study demonstrates that the ability toddlers exhibit is a more general one, namely, an ability to discriminate relative quantity. Using a square enclosure, we show that toddlers use the relative sizes of the figures on different walls to characterize different corners. We also show that they do not use simple non-relative features to distinguish different corners. Possible reasons for differences in the ability to use relative versus non-relative cues are discussed.

In the present paper we investigated the development of the ability to reproduce extent in elementary school students. Children were shown a target line in a frame and were asked to reconstruct the line in a frame of a different size. One experimental condition involved reproducing "absolute extent," i.e., drawing a line that would be equal in length to the target line. The other condition involved reproducing relative extent; drawing a line that would preserve the relation between the target line and the frame. We found that in both conditions the length of the target and its relation to the frame affected children's responses. Yet, older children (7-9-year-olds) showed distinctive response patterns in the two conditions, indicating differentiation between absolute and relative extent. Whereas the performance of 5-year-olds in reproducing relative extent was similar to that of older children, their reproduction of absolute extent reflected a compromise between the use of absolute and relative cues. These findings extend the results of prior work suggesting an early advantage in the ability to use relative rather than absolute extent. (Contains 4 figures and 1 table.)

This article examines caregiver speech to young children. The authors obtained several measures of the speech used to children during early language development (14-30 months). For all measures, they found substantial variation across individuals and subgroups. Speech patterns vary with caregiver education, and the differences are maintained over time. While there are distinct levels of complexity for different caregivers, there is a common pattern of increase across age within the range that characterizes each educational group. Thus, caregiver speech exhibits both long-standing patterns of linguistic behavior and adjustment for the interlocutor. This information about the variability of speech by individual caregivers provides a framework for systematic study of the role of input in language acquisition.

In this article, the authors present and test a formal model that holds that people use information about category boundaries in estimating inexactly represented stimuli. Boundaries restrict stimuli that are category members to fall within a particular range. This model posits that people increase the average accuracy of stimulus estimates by integrating fine-grain values with boundary information, eliminating extreme responses. The authors present 4 experiments in which people estimated sizes of squares from 2 adjacent or partially overlapping stimulus sets. When stimuli from the 2 sets were paired in presentation, people formed relative size categories, truncating their estimates at the boundaries of these categories. Truncation at the boundary of separation between the categories led to exaggeration of differences between stimuli that cross categories. Yet truncated values are shown to be more accurate on average than unadjusted values.

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.

This study examines the development of children's ability to reason about proportions that involve either discrete entities or continuous amounts. Six-, 8- and 10-year olds were presented with a proportional reasoning task in the context of a game involving probability. Although all age groups failed when proportions involved discrete quantities, even the youngest age group showed some success when proportions involved continuous quantities. These findings indicate that quantity type strongly affects children's ability to make judgments of proportion. Children's greater success in judging proportions involving continuous quantities appears to be related to their use of different strategies in the presence of countable versus noncountable entities. In two discrete conditions, children--particularly 8- and 10-year-olds--adopted an erroneous counting strategy, considering the number of target elements but not the relation between target and nontarget elements, either in terms of number or amount. In contrast, in the continuous condition, when it was not possible to count, children may have relied on an early developing ability to code the relative amounts of target and nontarget regions. (Contains 3 figures and 5 tables.)

The present study tests a model of category effects upon stimulus estimation in children. Prior work with adults suggests that people inductively generalize distributional information about a category of stimuli and use this information to adjust their estimates of individual stimuli in a way that maximizes average accuracy in estimation (see Huttenlocher, Hedges & Vevea, 2000). However, little is known about the developmental origin of this cognitive process. In the present study, 5- and 7-year-old children viewed stimuli that varied in size and reproduced each from memory. Consistent with the predictions of a Bayesian model of category effects on estimation, responses were adjusted toward the central value of the stimulus distribution. Additionally, the dispersion of the stimulus distribution affected the pattern of bias and variability of responses in a way that is predicted by the model. The results suggest that, like adults, children use categories for increasing average accuracy in estimating inexact stimuli.

Previous studies show that following disorientation children use the geometry of an enclosed space to locate an object hidden in one of the corners [e.g. (Harmer, L., & Spelke, E. (1996). Modularity and development: A case of spatial reorientation. "Cognition, 61," 195-232)]. These studies have used a disorientation procedure that involves rotating the viewer (with eyes closed). Here, we examine 18- to 25-month-olds' spatial coding in two disorientation tasks--involving either "viewer" or "space" rotation. Importantly, the rotational movements in both tasks could not be visually tracked. Children were tested in either task (viewer- or space-movement) from either inside or outside a triangular (isosceles) space (with one unique and two equivalent corners). In the viewer-movement task, performance was above chance, regardless of which corner contained the object. In the space-movement task, performance was above chance at only the unique corner. On both tasks, performance was better from inside the space than from outside. The implications for how children determine location are discussed.

Questions concerning the role of input in the growth of syntactic skills have generated substantial debate within psychology and linguistics. The authors address these questions by investigating the effects of experimentally manipulated input on children's skill with the passive voice. The study involved 72 four-year-olds who listened to stories containing either a high proportion of passive voice sentences or a high proportion of active voice sentences. Following 10 story sessions, children's production and comprehension of passives were assessed. Intervention type affected performance--children who heard stories with passive sentences produced more passive constructions (and with fewer mistakes) and showed higher comprehension scores than children who heard stories with active sentences. Theoretical implications of these results for the understanding of the nature of syntactic skills and practical implications for the development of preschool materials are discussed.

This study examined the relation between the amount of mathematical input in the speech of preschool or day-care teachers and the growth of children's conventional mathematical knowledge over the school year. Three main findings emerged. First, there were marked individual differences in children's conventional mathematical knowledge by 4 years of age that were associated with socioeconomic status. Second, there were dramatic differences in the amount of math-related talk teachers provided. Third, and most important, the amount of teachers' math-related talk was significantly related to the growth of preschoolers' conventional mathematical knowledge over the school year but was unrelated to their math knowledge at the start of the school year.

Two experiments tested the ability of 4- and 8-year-old children to encode the extent of a target dowel and later discriminate between the target and a foil having a novel extent. By manipulating the heights of containers in which we presented the stimuli we tested whether children used the relation between the dowels and containers for encoding extent. We found that 8-year-olds encoded extent without relying on the relation between the target dowel and container but 4-year-olds only encoded the extent of the target dowel relative to the container. This early ability to encode extent relative to an aligned standard may serve as a perceptual basis for the developing ability to measure. (Contains 1 figure and 1 table.)

This study explores how infants encode an object's spatial extent. We habituated 6.5-month-old infants to a dowel inside a container and then tested whether they dishabituate to a change in absolute size when the relation between dowel and container is held constant (by altering the size of both container and dowel) and when the relation changes (by altering only the size of the container but not the dowel). Infants only dishabituated when the relation changed, suggesting that they do not encode the absolute size of either object but only the relation between them. (Contains 2 figures.)

Four experiments are reported in which people organize a space hierarchically when they estimate particular locations in that space. Earlier work showed that people subdivide circles into quadrants bounded at the vertical and horizontal axes, biasing their estimates towards prototypical diagonal locations within those spatial categories (Psychological Review 98 (1991) 352). In this work Huttenlocher, Hedges, and Duncan showed that the use of such spatial categories can increase the accuracy of estimation of inexactly represented locations. The stimulus locations we examined were uniformly distributed across the circle. In the present study we explore whether variation in the distribution of locations affects how the circle is categorized. Other things being equal, categories that capture high density regions in a stimulus space should contribute most to accuracy of estimation. However, precision of boundaries is also important to accuracy; with imprecise boundaries stimuli may be misclassified, leading to large errors in estimation. We found that people use the same spatial categories regardless of the distribution of the locations. We argue that this spatial organization nevertheless can maximize the accuracy of estimates because vertical and horizontal category boundaries are the most exact, minimizing misclassification of stimuli.

The map is a small-scaled version of the space it represents. It has been argued that children have difficulty interpreting maps because they do not understand scale relations. Recent research has shown that even preschoolers can solve problems that involve scaling in one dimension. This study examined whether early scaling ability extends to tasks involving two-dimensional maps and referent spaces of different sizes. Results showed that about 60% of the 4-year-olds and 90% of the 5-year-olds tested used distance information presented on a map to locate an object in a two-dimensional spatial layout. Children had more difficulties in solving mapping tasks with a larger referent space. This decrease in accuracy as a function of space size on the mapping task was greater than would have been expected on the basis of performance on a parallel nonmapping task. The results are discussed in terms of their implications for the mechanisms underlying early scaling ability.

This paper presents three experiments which show syntactic priming effects in four- and five-year-old children. The experiments are modeled after priming studies with adults involving transitive and dative constructions. In Study 1 children were presented with a picture that was described by an experimenter. They repeated the experimenter's sentence and then were presented with a new picture to describe. Children were more likely to use a particular syntactic form if it had been used by the experimenter. In Study 2 the procedure was identical except that children did not repeat the experimenter's sentence. Priming effects were comparable to those in Study 1. In Study 3, after hearing the experimenter's sentences, children were presented with a block of pictures to describe. Across the entire block, children were more likely to use a particular form if it had been used by the experimenter. Together these results indicate that children represent syntactic form independently of particular lexical items.

Existing work on the acquisition of syntax has been concerned mainly with the early stages of syntactic development. In the present study we examine later syntactic development in children. Also, existing work has focused on commonalities in the emergence of syntax. Here we explore individual differences among children and their relation to variations in language input. In Study 1 we find substantial individual differences in children's mastery of multiclause sentences and a significant relation between those differences and the proportion of multiclause sentences in parent speech. We also find individual differences in the number of noun phrases in children's utterances and a significant relation between those differences and the number of noun phrases in parent speech. In Study 2 we find greater syntactic growth over a year of preschool in classes where teachers' speech is more syntactically complex. The implications of our findings for the understanding of the sources of syntactic development are discussed.

Six experiments examined whether there were circumstances in which toddlers could use landmarks for spatial reorientation. Findings confirmed that geometric information is used for reorientation by toddlers, but give reason to doubt that the use of this information is achieved using a module impenetrable to nongeometric information. (Author/KB)

Two experiments investigated infants' sensitivity to amount of continuous quantity and to changes in amount of continuous quantity. Found that 6-month-olds looked significantly longer at a novel quantity than at the familiar quantity. Nine-month-olds looked significantly longer at an impossible event than at a possible event. Findings question claims that infants' quantitative mechanism is exclusive to number. (Author/KB)

Tested 3- to 7-year-olds' ability to calculate with whole numbers, fractions, and mixed-numbers, in a task in which an amount was displayed, then hidden. Subjects were to determine the hidden amount resulting when numbers were added or substracted. Found that, although fraction problems were more difficult than whole-number problems, competence on all problem types emerged in the early childhood period. (JPB)

Examined sex differences in 4- to 6-year olds' spatial skill. Found that performance on spatial transformation task showed a substantial male advantage by age 4 years 6 months, with the advantage no more robust for rotation than for translation items. Comparable vocabulary task performance indicated that male advantage on spatial tasks was not attributable to overall intellectual advantage. (Author/KB)

Examined the relationship of environmental input to cognitive growth in language, spatial operations, concepts, and associative memory in children tested four times six months apart and differing in the amount of school input received. Found that children made greater growth over periods with greater amounts of school input for language, spatial operations, and concepts, but not associative memory. (Author/KB)

In four experiments, three, four, and five year olds were successful in solving perspective-taking problems when they were asked what object occupied a specified location with respect to a hypothetical observer. Results indicated developmental change in several important aspects of spatial performance. (BC)