The role of embodied intention in early lexical acquisition

We examine the influence of inferring interlocutors' referential intentions from their body movements at the early stage of lexical acquisition. By testing human participants and comparing their performances in different learning conditions, we find that those embodied intentions facilitate both word discovery and word-meaning association. In light of empirical findings, the main part of this article presents a computational model that can identify the sound patterns of individual words from continuous speech, using nonlinguistic contextual information, and employ body movements as deictic references to discover word-meaning associations. To our knowledge, this work is the first model of word learning that not only learns lexical items from raw multisensory signals to closely resemble infant language development from natural environments, but also explores the computational role of social cognitive skills in lexical acquisition.     

Comparing Multiple Paths to Mastery: What is Learned?

Contemporary theories of learning postulate one or at most a small number of different learning mechanisms. However, people are capable of mastering a given task through qualitatively different learning paths such as learning by instruction and learning by doing. We hypothesize that the knowledge acquired through such alternative paths differs with respect to the level of abstraction and the balance between declarative and procedural knowledge. In a laboratory experiment we investigated what was learned about patterned letter sequences via either direct instruction in the relevant patterns or practice in solving letter-sequence extrapolation problems. Results showed that both types of learning led to mastery of the target task as measured by accuracy performance. However, behavioral differences emerged in how participants applied their knowledge. Participants given instruction showed more variability in the types of strategies they used to articulate their knowledge as well as longer solution times for generating the action implications of that knowledge as compared to the participants given practice. Results are discussed regarding the implications for transfer, generalization, and procedural application. Learning theories that claim generality should be tested against cross-scenario phenomena, not just parametric variations of a single learning scenario.     

Modeling parallelization and flexibility improvements in skill acquisition: from dual tasks to complex dynamic skills

Emerging parallel processing and increased flexibility during the acquisition of cognitive skills form a combination that is hard to reconcile with rule-based models that often produce brittle behavior. Rule-based models can exhibit these properties by adhering to 2 principles: that the model gradually learns task-specific rules from instructions and experience, and that bottom-up processing is used whenever possible. In a model of learning perfect time-sharing in dual tasks (Schumacher et al., 2001), speedup learning and bottom-up activation of instructions can explain parallel behavior. In a model of a complex dynamic task (Carnegie Mellon University Aegis Simulation Program [CMU-ASP], Anderson et al., 2004), parallel behavior is explained by the transition from serially organized instructions to rules that are activated by both top-down (goal-driven) and bottom-up (perceptually driven) factors. Parallelism lets the model opportunistically reorder instructions, leading to the gradual emergence of new task strategies.     

Use of phonetic specificity during the acquisition of new words: differences between consonants and vowels

The present study explores the issue of the use of phonetic specificity in the process of learning new words at 20 months of age. The procedure used follows Nazzi and Gopnik [Nazzi, T., & Gopnik, A. (2001). Linguistic and cognitive abilities in infancy: When does language become a tool for categorization? Cognition, 80, B11-B20]. Infants were first presented with triads of perceptually dissimilar objects, which were given made-up names, two of the objects receiving the same name. Then, word learning was evaluated through object selection/categorization. Tests involved phonetically different words (e.g. [pize] vs. [mora], Experiment 1), words differing minimally on their onset consonant (e.g. [pize] vs. [tize], Experiment 2a), and conditions which had never been tested before: non-initial consonantal contrasts (e.g. [pide] vs. [pige], Experiment 2b), and vocalic contrasts (e.g. [pize] vs. [pyze]; [pize] vs. [paze]; [pize] vs. [pizu], Experiments 3a-c). Results differed across conditions: words could be easily learnt in the phonetically different condition, and were learnt, though to a lesser degree, in both the initial and non-initial minimal consonant contrast; however, infants' global performance on all three vocalic contrasts was at chance level. The present results shed new light regarding the specificity of early words, and raise the possibility of different contributions for vowels and consonants in early word learning.     

Infants learn phonotactic regularities from brief auditory experience

Two experiments investigated whether novel phonotactic regularities, not present in English, could be acquired by 16.5-month-old infants from brief auditory experience. Subjects listened to consonant-vowel-consonant syllables in which particular consonants were artificially restricted to either initial or final position (e.g. /baep/ not /paeb/). In a later head-turn preference test, infants listened longer to new syllables that violated the experimental phonotactic constraints than to new syllables that honored them. Thus, infants rapidly learned phonotactic regularities from brief auditory experience and extended them to unstudied syllables, documenting the sensitivity of the infant's language processing system to abstractions over linguistic experience.     

Infants' understanding of false labeling events: the referential roles of words and the speakers who use them

The four studies reported here examine whether 16-month-old infants' responses to true and false utterances interact with their knowledge of human agents. In Study 1, infants heard repeated instances either of true or false labeling of common objects; labels came from an active human speaker seated next to the infant. In Study 2, infants experienced the same stimuli and procedure; however, we replaced the human speaker of Study 1 with an audio speaker in the same location. In Study 3, labels came from a hidden audio speaker. In Study 4, a human speaker labeled the objects while facing away from them. In Study 1, infants looked significantly longer to the human agent when she falsely labeled than when she truthfully labeled the objects. Infants did not show a similar pattern of attention for the audio speaker of Study 2, the silent human of Study 3 or the facing-backward speaker of Study 4. In fact, infants who experienced truthful labeling looked significantly longer to the facing-backward labeler of Study 4 than to true labelers of the other three contexts. Additionally, infants were more likely to correct false labels when produced by the human labeler of Study 1 than in any of the other contexts. These findings suggest, first, that infants are developing a critical conception of other human speakers as truthful communicators, and second, that infants understand that human speakers may provide uniquely useful information when a word fails to match its referent. These findings are consistent with the view that infants can recognize differences in knowledge and that such differences can be based on differences in the availability of perceptual experience.     

Children's comprehension of sentences with focus particles

We report three studies investigating children's and adults' comprehension of sentences containing the focus particle only. In Experiments 1 and 2, four groups of participants (6-7 years, 8-10 years, 11-12 years and adult) compared sentences with only in different syntactic positions against pictures that matched or mismatched events described by the sentence. Contrary to previous findings (Crain, S., Ni, W., & Conway, L. (1994). Learning, parsing and modularity. In C. Clifton, L. Frazier, & K. Rayner (Eds.), Perspectives on sentence processing. Hillsdale, NJ: Lawrence Erlbaum; Philip, W., & Lynch, E. (1999). Felicity, relevance, and acquisition of the grammar of every and only. In S. C. Howell, S. A. Fish, & T. Keith-Lucas (Eds.), Proceedings of the 24th annual Boston University conference on language development. Somerville, MA: Cascadilla Press) we found that young children predominantly made errors by failing to process contrast information rather than errors in which they failed to use syntactic information to restrict the scope of the particle. Experiment 3 replicated these findings with pre-schoolers.     

A narwhal is an animal: partial word knowledge biases adults' decisions

Adults' accuracy on a sentence verification task was measured to assess reliable biases in their responses as a function of their level of knowledge about the target words, as well as adults' ability to reject incorrect ontological category membership for their partially known words. Three levels of word knowledge (known, frontier, and unknown) were assessed in two experiments. Results indicated that participants were conservative decision-makers about sentences using the vocabulary words and that the conservative bias increased in strength as their level of knowledge about the target word increased. When biased guessing was discouraged, results indicated that participants were able to accurately identify both correct and incorrect sentences using targets at all three levels of knowledge, including their partially known words, but were least reliable at rejecting false sentences using unknown targets. Implications for the role of knowing not in adults' vocabulary acquisition are discussed.     

The Neural Basis of Motor-Skill Learning

Recent work indicates that motor-skill learning is supported by four processes: a strategic process that selects new goals of what to change in the environment, a perceptual-motor integration process that adjusts to new relationships between environmental stimuli and the appropriate motor response, a sequencing process that learns sequences of motor acts, and a dynamic process that learns new patterns of muscle activations. These four processes can operate in one of two modes: an unconscious mode, in which one is aware only of the goal of the movement, or a conscious mode, in which one consciously controls detailed aspects of the movement. This article provides an overview of these four processes and two modes, and describes their neural bases.     

Response acquisition with delayed reinforcement: a comparison of two-lever procedures.

Groups of 8 experimentally naive rats were exposed during 8-hr sessions to resetting delay procedures in which responses on one lever (the reinforcement lever) produced water after a delay of 8, 16, 32, or 64 s. For rats in one condition, responses on a second (no-consequences) lever had no programmed consequences. For rats in another condition, responses on a second (cancellation) lever during a delay initiated by a response on the reinforcement lever prevented delivery of the scheduled reinforcer; responses on the cancellation lever at other times had no programmed consequences. Under both conditions and at all delays, most subjects emitted more responses on the reinforcement lever than did control rats that never received water emitted on either lever. At 8-s delays, both conditions engendered substantially more responding on the reinforcement lever than on the other lever, and performance closely resembled that of immediate-reinforcement controls. At delays of 16 and 32 s, however, there was clear differential responding on the two levers under the cancellation condition but not under the other condition. When the delay was 64 s, differential responding on the two levers did not occur consistently under either condition. These findings provide strong evidence that the behavior of rats is sensitive to consequences delayed by 8, 16, and 32 s, but only equivocal evidence of such sensitivity to consequences delayed 64 s. They also indicate that acquisition depends, in part, on the measure of performance used to index it.