Lynn K. Perry

Learn Locally, Think Globally Exemplar Variability Supports Higher-Order Generalization and Word Learning

Research suggests that variability of exemplars supports successful object categorization; however, the scope of variability’s support at the level of higher-order generalization remains unexplored. Using a longitudinal study, we examined the role of exemplar variability in first- and second-order generalization in the context of nominal-category learning at an early age. Sixteen 18-month-old children were taught 12 categories. Half of the children were taught with sets of highly similar exemplars; the other half were taught with sets of dissimilar, variable exemplars. Participants’ learning and generalization of trained labels and their development of more general word-learning biases were tested. All children were found to have learned labels for trained exemplars, but children trained with variable exemplars generalized to novel exemplars of these categories, developed a discriminating word-learning bias generalizing labels of novel solid objects by shape and labels of nonsolid objects by material, and accelerated in vocabulary acquisition. These findings demonstrate that object variability leads to better abstraction of individual and global category organization, which increases learning outside the laboratory.

The Shape of the Vocabulary Predicts the Shape of the Bias

Children acquire attentional biases that help them generalize novel words to novel objects. Researchers have proposed that these biases arise from regularities in the early noun vocabulary children learn and suggest that the specifics of the biases should be tied to the specifics of individual children’s vocabularies. However, evidence supporting this proposal to date comes from studies of group means. The current study examines the relations between the statistics of the nouns young children learn and the similarities and differences in the biases they demonstrate. We show that individual differences in vocabulary structure predict individual differences in novel noun generalization. Thus, these data support the proposal that word learning biases emerge from the regularities present in individual children’s vocabularies and, importantly, that children’s on-line attention during an experiment is mediated by instances of past learning.

Highchair philosophers: the impact of seating context-dependent exploration on children's naming biases

We examine developmental interactions between context, exploration, and word learning. Infants show an understanding of how nonsolid substances are categorized that does not reliably transfer to learning how these categories are named in laboratory tasks. We argue that what infants learn about naming nonsolid substances is contextually bound - most nonsolids that toddlers are familiar with are foods and thus, typically experienced when sitting in a highchair. We asked whether 16-month-old childrens naming of nonsolids would improve if they were tested in that typical context. Children tested in the highchair demonstrated better understanding of how nonsolids are named. Furthermore, context-based differences in exploration drove differences in the properties attended to in real-time. We discuss what implications this context-dependency has for understanding the development of an ontological distinction between solids and nonsolids. Together, these results demonstrate a developmental cascade between context, exploration, and word learning.

The role of language in multi-dimensional categorization: Evidence from transcranial direct current stimulation and exposure to verbal labels

Human concepts differ in their dimensionality. Some, like green-things, require representing one dimension while abstracting over many others. Others, like bird, have higher dimensionality due to numerous category-relevant properties (feathers, two-legs). Converging evidence points to the importance of verbal labels for forming low-dimensional categories. We examined the role of verbal labels in categorization by (1) using transcranial direct current stimulation over Wernickes area (2) providing explicit verbal labels during a category learning task. We trained participants on a novel perceptual categorization task in which categories could be distinguished by either a uni- or bi-dimensional criterion. Cathodal stimulation over Wernickes area reduced reliance on single-dimensional solutions, while presenting informationally redundant novel labels reduced reliance on the dimension that is normally incidental in the real world. These results provide further evidence that implicit and explicit verbal labels support the process of human categorization.

What the online manipulation of linguistic activity can tell us about language and thought.

Questions about the relationship between language and thought have long fascinated psychologists, philosophers, and the general public. One specific question is the extent to which verbal labels causally impact cognitive processes—how does calling an object by a particular name influence the way people categorize it; how does knowing words for mental states influence our reasoning about the minds of others; how does learning and using words like left influence our navigation behavior? One way to learn how the words we use to label objects, mental states, or locations affect our thoughts is to increase or decrease the ease with which we can use these words and observe outcomes of these manipulations on “non-linguistic” tasks. For example, if the word left enables us to remember which way to turn, preventing its activation might be expected to disrupt navigation. Manipulating the labeling process (and the engagement of language more broadly) is therefore very useful in exploring how language influences cognition. In this paper, we review two methodologies for implementing linguistic manipulations: verbal interference and transcranial direct current stimulation (tDCS), and discuss what we can learn about the role of language in cognitive processes from this line of research.

To have and to hold: looking vs. touching in the study of categorization

In order to make sense of the “blooming, buzzing, confusion” of a world where no two objects or events are ever exactly identical, infants form categories of perceptually distinct items that can be treated equivalently. The study of categorization often arises from one of two motivations: (1) to examine the mechanisms by which infants learn to treat distinct objects/events as equivalent (e.g., how an infant comes to name two different animals dog) and (2) to examine the current state of an infants knowledge (e.g., does an infant have a category of dog?). As an illustration, consider Quinn et al.s (1993) study. After habituating to different dog pictures, 3- and 4-month-olds do not dishabituate to cats. However, after habituating to cats, they do dishabituate to dogs. If we were examining the current state of knowledge, what should we conclude? Unless we want to suggest these infants are participants in Schrodingers thought experiment (1935)—they both have and do not have a cat category—we cannot say anything conclusive. Instead, the results reveal something important about the mechanisms of categorization. Quinn et al. (1993) showed variability between category members affects the exclusivity of the categories infants form. This example demonstrates that studying whether infants have a category misses the crucial point that categories are neither things that people have in their heads nor that exist in the world; but rather categorization is a process (see also Oakes and Madole, 2000; Samuelson and Smith, 2000; Samuelson et al., 2007). In addition to these two main motivations, the study of categorization typically utilizes one of two methodologies: (1) looking measures, e.g., habituation and preferential looking, and (2) touching/reaching measures, e.g., sequential touching or manual forced choice measures. What I will argue in this paper is that looking measures (1) too readily lend themselves to interpretations of infants having a category or not, and (2) miss the importance the body and physical context have on development.

Aligning body and world: stable reference frames improve young children's search for hidden objects.

This study investigated how young childrens increasingly flexible use of spatial reference frames enables accurate search for hidden objects by using a task that 3-year-olds have been shown to perform with great accuracy and 2-year-olds have been shown to perform inaccurately. Children watched as an object was rolled down a ramp, behind a panel of doors, and stopped at a barrier visible above the doors. In two experiments, we gave 2- and 2.5-year-olds a strong reference frame by increasing the relative salience and stability of the barrier. In Experiment 1, 2.5-year-olds performed at above-chance levels with the more salient barrier. In Experiment 2, we highlighted the stability of the barrier (or ramp) by maximizing the spatial extent of each reference frame across the first four training trials. Children who were given a stable barrier (and moving ramp) during these initial trials performed at above-chance levels and significantly better than children who were given a stable ramp (and moving barrier). This work highlights that factors central to spatial cognition and motor planning-aligning egocentric and object-centered reference frames-play a role in the ramp task during this transitional phase in development.

A year in words: The dynamics and consequences of language experiences in an intervention classroom

Children from low SES backgrounds hear, on average, fewer words at home than those from high SES backgrounds. This word gap is associated with widening achievement differences in children’s language abilities and school readiness. However relatively little is known about adult and child speech in childcare settings, in which approximately 30% of American children are enrolled. We examined the influence of teacher and peer language input on children’s in-class language use and language development in an intervention classroom for low-SES, high-risk 2- to 3-year-olds. Over the course of a year, day-long recordings of the classroom were collected weekly with LENA recorders. Using LENA software algorithms, we found that language input from peers was positively related to children’s in-class language use, both in-the-moment and over the course of each day, as were the number of conversational turns in which children and teachers engaged Both peer input and conversational turns with teachers were also positively related to children’s language development rates, as indexed by increases in vocabulary size. Together these results indicate the importance of child-specific rates of classroom language input in the language development of high-risk, preschoolers.

Language as shaped by the brain; the brain as shaped by development

Though we agree with their argument that language is shaped by domain-general learning processes, Christiansen & Chater (C&C) neglect to detail how the development of these processes shapes language change. We discuss a number of examples that show how developmental processes at multiple levels and timescales are critical to understanding the origin of domain-general mechanisms that shape language evolution.