Larissa K. Samuelson

Object name Learning Provides On-the-Job Training for Attention

By the age of 3, children easily learn to name new objects, extending new names for unfamiliar objects by similarity in shape. Two experiments tested the proposal that experience in learning object names tunes childrens attention to the properties relevant for naming—in the present case, to the property of shape—and thus facilitates the learning of more object names. In Experiment 1, a 9-week longitudinal study, 17-month-old children who repeatedly played with and heard names for members of unfamiliar object categories well organized by shape formed the generalization that only objects with similar shapes have the same name. Trained children also showed a dramatic increase in acquisition of new object names outside of the laboratory during the course of the study. Experiment 2 replicated these findings and showed that they depended on childrens learning both a coherent category structure and object names. Thus, children who learn specific names for specific things in categories with a common organizing property—in this case, shape—also learn to attend to just the right property—in this case, shape—for learning more object names.

Early noun vocabularies: do ontology, category structure and syntax correspond?

This paper examines childrens early noun vocabularies and their interpretations of names for solid and non-solid things. Previous research in this area assumes that ontology, category organization and syntax correspond in the nouns children learn early such that categories of solid things are organized by shape similarity and named with count nouns and categories of non-solid things are organized by material similarity and named with mass nouns. In Experiment 1 we examine the validity of this assumption in a corpus of early-learned nouns and conclude that one side of the solidity-syntax-category organization mapping is favored. In our second experiment we examine the relation between early noun vocabulary development and novel word generalization. We find that children between 17 and 33 months of age do not systematically generalize names for solid things by shape similarity until they already know many nouns, and do not systematically generalize names for non-solid substances by material similarity. The implications for childrens acquisition of the ontological distinction, count/mass syntax, and novel nouns are discussed.

Fast Mapping but Poor Retention by 24-Month-Old Infants

Four experiments explored the processes that bridge between referent selection and word learning. Twenty-four-month-old infants were presented with several novel names during a referent selection task that included both familiar and novel objects and tested for retention after a 5-min delay. The 5-min delay ensured that word learning was based on retrieval from long-term memory. Moreover, the relative familiarity of objects used during the retention test was explicitly controlled. Across experiments, infants were excellent at referent selection, but very poor at retention. Although the highly controlled retention test was clearly challenging, infants were able to demonstrate retention of the first 4 novel names presented in the session when referent selection was augmented with ostensive naming. These results suggest that fast mapping is robust for reference selection but might be more transient than previously reported for lexical retention. The relations between reference selection and retention are discussed in terms of competitive processes on 2 timescales: competition among objects on individual referent selection trials and competition among multiple novel name-object mappings made across an experimental session.

Word Learning Emerges from the Interaction of Online Referent Selection and Slow Associative Learning.

Classic approaches to word learning emphasize referential ambiguity: In naming situations, a novel word could refer to many possible objects, properties, actions, and so forth. To solve this, researchers have posited constraints, and inference strategies, but assume that determining the referent of a novel word is isomorphic to learning. We present an alternative in which referent selection is an online process and independent of long-term learning. We illustrate this theoretical approach with a dynamic associative model in which referent selection emerges from real-time competition between referents and learning is associative (Hebbian). This model accounts for a range of findings including the differences in expressive and receptive vocabulary, cross-situational learning under high degrees of ambiguity, accelerating (vocabulary explosion) and decelerating (power law) learning, fast mapping by mutual exclusivity (and differences in bilinguals), improvements in familiar word recognition with development, and correlations between speed of processing and learning. Together it suggests that (a) association learning buttressed by dynamic competition can account for much of the literature; (b) familiar word recognition is subserved by the same processes that identify the referents of novel words (fast mapping); (c) online competition may allow the children to leverage information available in the task to augment performance despite slow learning; (d) in complex systems, associative learning is highly multifaceted; and (e) learning and referent selection, though logically distinct, can be subtly related. It suggests more sophisticated ways of describing the interaction between situation- and developmental-time processes and points to the need for considering such interactions as a primary determinant of development.

Statistical regularities in vocabulary guide language acquisition in connectionist models and 15-20-month-olds

This research tested the hypothesis that young childrens bias to generalize names for solid objects by shape is the product of statistical regularities among nouns in the early productive vocabulary. Data from a 4-layer Hopfield network suggested that the statistical regularities in the early noun vocabulary are strong enough to create a shape bias, and that the shape bias is overgeneralized to nonsolid stimuli. A 2nd simulation suggested that this overgeneralization is due to the dominance of names for shape-based categories in the early noun vocabulary. Two subsequent longitudinal experiments tested whether it is possible to create word learning biases in children. Children 15-20 months old were given intensive naming experiences with 12 noun categories typical of the types of categories children learn to name early. The children developed a precocious shape bias that was overgeneralized to naming nonsolid substances; they also showed accelerated vocabulary development. Children taught an atypical set of nouns or no new nouns did not develop a shape bias and did not show accelerated vocabulary development.

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.

Grounding Development in Cognitive Processes.

Developmentalists have made remarkable progress over the last several decades in detailing what children know at various points in development. Less progress has been made, however, in detailing the processes through which knowledge is realized in real-time tasks, or in detailing the processes of developmental change. We argue that the operating characteristics of perceiving and remembering provide a foundation for making progress on these issues in the next century. We include three examples applying these ideas to specific phenomena in early word learning. These examples illustrate how forming developmental hypotheses in terms of perceiving and remembering may bring new insights into specific phenomena as well as into how the ordinary operating characteristics of perceiving and remembering serve as bootstraps to more specialized and more abstract kinds of knowledge.

What's New? Children Prefer Novelty in Referent Selection.

Determining the referent of a novel name is a critical task for young language learners. The majority of studies on childrens referent selection focus on manipulating the sources of information (linguistic, contextual and pragmatic) that children can use to solve the referent mapping problem. Here, we take a step back and explore how childrens endogenous biases towards novelty and their own familiarity with novel objects influence their performance in such a task. We familiarized 2-year-old children with previously novel objects. Then, on novel name referent selection trials children were asked to select the referent from three novel objects: two previously seen and one completely novel object. Children demonstrated a clear bias to select the most novel object. A second experiment controls for pragmatic responding and replicates this finding. We conclude, therefore, that childrens referent selection is biased by previous exposure and childrens endogenous bias to novelty.

Children's Attention to Rigid and Deformable Shape in Naming and Non-Naming Tasks.

In four experiments with three-year-olds (N = 67), we investigate childrens understanding of the differential importance of shape for categorization of solid rigid objects with fixed shapes and solid but deformable objects with shapes that can be changed. In a non-naming task we find that young children categorize rigid and deformable things differently and know that material is important for deformable things and shape for rigid things. In two naming tasks, however, children generalize names for both solid and deformable objects by shape similarity and disregard rigidity. To understand this pattern of results we examine a corpus of early-learned nouns and the kinds of rigid and nonrigid things named by nouns in that corpus. The results suggest that names for categories of solid, rigid objects in which instances are similar in shape dominate childrens early noun vocabularies. We suggest that childrens novel word generalizations for deformable things may be overgeneralizations of this dominant pattern.

Different is good: connectionism and dynamic systems theory are complementary emergentist approaches to development

Connectionist and dynamic systems approaches to development are similar in that they are both emergentist theories that take a very different perspective from more traditional symbolic systems. Moreover, they are both based on similar mathematical principles. Nevertheless, connectionism and dynamic systems differ in the approach they take to the study of development. We argue that differences between connectionist and dynamic systems approaches in terms of the basic components of the models, what they see as the object of study, how they view the nature of knowledge and their notions of developmental change mean that they each stand to make different and unique contributions to a more complete theory of development. We present an example from our work on how children learn to learn words that illustrates the complementary nature of connectionist and dynamic systems theories.