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.     

The importance of contextual elements in taste-aversion learning

The effect of exteroceptive contextual cues, presented during the conditioned stimulus (CS) and unconditioned stimulus (US) intervals, upon the later development of conditioned saccharin aversions was studied in two experiments. It was found that the presence of the contextual cues during the CS + US and CS intervals resulted in a greater degree of saccharin aversion; the presence of these cues during the US interval was relatively less important. These findings are discussed in terms of conditioning models and retrieval models derived from animal learning and human information-processing data.     

A cross-linguistic study of early lexical development

Cross-linguistic studies have shown that children can vary markedly in rate, style, and sequence of grammatical development, within and across natural languages. It is less clear whether there are robust cross-linguistic differences in early lexical development, with particular reference to the onset and rate of growth in major lexical categories (e.g., nouns, verbs, adjectives and grammatical function words). In this study, we present parental report data on the first stages of expressive and receptive lexical development for 659 English infants and 195 Italian infants between 8 and 16 months of age. Although there are powerful structural differences between English and Italian that could affect the order in which nouns and verbs are acquired, no differences were observed between these languages in the emergence and growth of lexical categories. In both languages, children begin with words that are difficult to classify in adult part-of-speech categories (i.e., “routines”). This is followed by a period of sustained growth in the proportion of vocabulary contributed by common nouns. Verbs, adjectives, and grammatical function words are extremely rare until children have vocabularies of at least 100 words. The same sequences are observed in production and comprehension, although verbs are reported earlier for receptive vocabulary. Our results are compared with other reports in the literature, with special reference to recent claims regarding the early emergence of verbs in Korean.     

Dynamic self-organization and early lexical development in children

In this study we present a self-organizing connectionist model of early lexical development. We call this model DevLex-II, based on the earlier DevLex model. DevLex-II can simulate a variety of empirical patterns in children's acquisition of words. These include a clear vocabulary spurt, effects of word frequency and length on age of acquisition, and individual differences as a function of phonological short-term memory and associative capacity. Further results from lesioned models indicate developmental plasticity in the network's recovery from damage, in a non-monotonic fashion. We attribute the network's abilities in accounting for lexical development to interactive dynamics in the learning process. In particular, variations displayed by the model in the rate and size of early vocabulary development are modulated by (a) input characteristics, such as word frequency and word length, (b) consolidation of lexical-semantic representation, meaning-form association, and phonological short-term memory, and (c) delayed processes due to interactions among timing, severity, and recoverability of lesion. Together, DevLex and DevLex-II provide an accurate computational account of early lexical development.     

The absence of a shape bias in children's word learning

There is debate about whether preschool-age children interpret words as referring to kinds or to classes defined by shape similarity. The authors argue that the shape bias reported in previous studies is a task-induced artifact rather than a genuine word-learning strategy. In particular, children were forced to extend an object's novel label to one of several stand-alone, simple-shaped items, including a same-shape option from a different category and a different-shape option from the same superordinate category. Across 6 experiments, the authors found that the shape bias was eliminated (a) when the objects were more complex, (b) when they were presented in context, or (c) when children were no longer forced to choose. Moreover, children preferred the different-shape category alternatives when these were part of the same basic-level category as the target. The present experiments suggest that children seek out objects of the same kind when presented with a novel label, even if they are sometimes unable to identify the relevant kinds on their own.     

The importance of internal facial features in learning new faces

For familiar faces, the internal features (eyes, nose, and mouth) are known to be differentially salient for recognition compared to external features such as hairstyle. Two experiments are reported that investigate how this internal feature advantage accrues as a face becomes familiar. In Experiment 1, we tested the contribution of internal and external features to the ability to generalize from a single studied photograph to different views of the same face. A recognition advantage for the internal features over the external features was found after a change of viewpoint, whereas there was no internal feature advantage when the same image was used at study and test. In Experiment 2, we removed the most salient external feature (hairstyle) from studied photographs and looked at how this affected generalization to a novel viewpoint. Removing the hair from images of the face assisted generalization to novel viewpoints, and this was especially the case when photographs showing more than one viewpoint were studied. The results suggest that the internal features play an important role in the generalization between different images of an individual's face by enabling the viewer to detect the common identity-diagnostic elements across non-identical instances of the face.     

The importance of decision making in causal learning from interventions

Recent research has focused on how interventions benefit causal learning. This research suggests that the main benefit of interventions is in the temporal and conditional probability information that interventions provide a learner. But when one generates interventions, one must also decide what interventions to generate. In three experiments, we investigated the importance of these decision demands to causal learning. Experiment 1 demonstrated that learners were better at learning causal models when they observed intervention data that they had generated, as opposed to observing data generated by another learner. Experiment 2 demonstrated the same effect between self-generated interventions and interventions learners were forced to make. Experiment 3 demonstrated that when learners observed a sequence of interventions such that the decision-making process that generated those interventions was more readily available, learning was less impaired. These data suggest that decision making may be an important part of causal learning from interventions.     

Looking through phonological shape to lexical meaning: The bottleneck of non-native sign language processing

In two studies, we find that native and non-native acquisition show different effects on sign language processing. Subjects were all born deaf and used sign language for interpersonal communication, but first acquired it at ages ranging from birth to 18. In the first study, deaf signers shadowed (simultaneously watched and reproduced) sign language narratives given in two dialects, American Sign Language (ASL) and Pidgin Sign English (PSE), in both good and poor viewing conditions. In the second study, deaf signers recalled and shadowed grammatical and ungrammatical ASL sentences. In comparison with non-native signers, natives were more accurate, comprehended better, and made different kinds of lexical changes; natives primarily changed signs in relation to sign meaning independent of the phonological characteristics of the stimulus. In contrast, non-native signers primarily changed signs in relation to the phonological characteristics of the stimulus independent of lexical and sentential meaning. Semantic lexical changes were positively correlated to processing accuracy and comprehension, whereas phonological lexical changes were negatively correlated. The effects of non-native acquisition were similar across variations in the sign dialect, viewing condition, and processing task. The results suggest that native signers process lexical structural automatically, such that they can attend to and remember lexical and sentential meaning. In contrast, non-native signers appear to allocate more attention to the task of identifying phonological shape such that they have less attention available for retrieval and memory of lexical meaning.     

Consequences of lexical stress on learning an artificial lexicon

Four experiments examined effects of lexical stress on lexical access for recently learned words. Participants learned artificial lexicons (48 words) containing phonologically similar items and were tested on their knowledge in a 4-alternative forced-choice (4AFC) referent-selection task. Lexical stress differences did not reduce confusions between cohort items: KAdazu and kaDAzeI were confused with one another in a 4AFC task and in gaze fixations as often as BOsapeI and BOsapaI. However, lexical stress did affect the relative likelihood of stress-initial confusions when words were embedded in running nonsense speech. Words with medial stress, regardless of initial vowel quality, were more prone to confusions than words with initial stress. The authors concluded that non-initial stress, particularly when wor segmentation is difficult, may serve as "noise" that alters lexical learning and lexical access.     

Levels-of-processing effects on Chinese character completion: The importance of lexical processing and test cue

The levels of processing (LoP) effect was studied in Chinese character completion tasks. The same stem cue, either graphemically or semantically related to the target character, was used to generate either a perceptual or a conceptual test. Participants received either direct or indirect instructions, so that the same stem cue also produced either an explicit or an implicit test of memory. This allowed us to examine simultaneously the roles of perceptual versus conceptual test and retrieval intentionality in the LoP effect. No LoP effects were found when the memory test was implicit. LoP effects were also not found for stems and characters related graphemically (perceptually), but were found for stems and characters related semantically (conceptually) when the memory test was explicit. The results are discussed in terms of the importance of lexical processing for character completion tests and the importance of reinstatement of the study process during retrieval for explicit memory tests.     

The role of novelty in early word learning

What mechanism implements the mutual exclusivity bias to map novel labels to objects without names? Prominent theoretical accounts of mutual exclusivity (e.g., Markman, 1989, 1990 ) propose that infants are guided by their knowledge of object names. However, the mutual exclusivity constraint could be implemented via monitoring of object novelty (see Merriman, Marazita, & Jarvis, 1995 ). We sought to discriminate between these contrasting explanations across two preferential looking experiments with 22‐month‐olds. In Experiment 1, infants viewed three objects: one name‐known, two name‐unknown. Of the two name‐unknown objects, one was novel, and the other had been previously familiarized. The infants responded to hearing a novel label by increasing attention only to the novel, name‐unknown object. In a second experiment in which the name‐known object was absent, a novel label increased infants’ attention to a novel object beyond baseline preference for novelty. The experiments provide clear evidence for a novelty‐based mechanism. However, differences in the time course of disambiguation across experiments suggest that novelty processing may be influenced by contextual factors.     

The importance of monitoring and self-regulation during multitrial learning

Theory suggests that accuracy of metacognitive monitoring and self-regulation of study will affect test performance, but there is little empirical evidence linking these variables. I examined the relation among these variables in a multitrial learning task. Regression analyses showed that monitoring accuracy and self-regulation were reliably related to test performance--greater monitoring accuracy and more effective self-regulation were associated with greater test performance. These analyses were contrasted with analyses typically conducted in previous research, to show the importance of using a multitrial learning task and of attending to the theoretically based causal relation among variables when evaluating how monitoring accuracy and self-regulation are related to test performance. The results of this investigation may help to explain why previous research has failed to link these variables.     

Beyond stop consonants: Consonantal specificity in early lexical acquisition

Previous research has shown that 20-month-old infants can simultaneously learn two words that only differ by one of their consonants, but fail to do so when the words differ only by one of their vowels. This asymmetry was interpreted as developmental evidence for the proposal that consonants play a more important role than vowels in lexical specification. However, the consonant/vowel distinction was confounded with another distinction, that of the continuous status of the phonemes used (discontinuous stop consonants versus continuous vowels). The present study investigated 20-month-olds’ use of phonetic specificity while simultaneously learning two words that differ by a continuous consonant. The results obtained parallel those previously found for stop consonants, confirming the original claim of an asymmetry between the roles of consonants and vowels at the lexical level.     

On leveraged learning in lexical acquisition and its relationship to acceleration

Children at about age 18 months experience acceleration in word learning. This vocabulary explosion is a robust phenomenon, although the exact shape and timing vary from child to child. One class of explanations, which we term collectively as leveraged learning , posits that knowledge of some words helps with the learning of others. In this framework, the child initially knows no words and so learning is slow. As more words are acquired, new words become easier and thus it is the acquisition of early words that fuels the explosion in learning. In this paper we examine the role of leveraged learning in the vocabulary spurt by proposing a simple model of leveraged learning. Our results show that leverage can change both the shape and timing of the acceleration, but that it cannot create acceleration if it did not exist in the corresponding model without leveraging. This model is then applied to the Zipfian distribution of word frequencies, which confirm that leveraging does not create acceleration, but that the relationship between frequency and the difficulty of learning a word may be complex.     

Multiple regression analyses in artificial-grammar learning: The importance of control groups

In artificial-grammar learning, it is crucial to ensure that above-chance performance in the test stage is due to learning in the training stage but not due to judgemental biases. Here we argue that multiple regression analysis can be successfully combined with the use of control groups to assess whether participants were able to transfer knowledge acquired during training when making judgements about test stimuli. We compared the regression weights of judgements in a transfer condition (training and test strings were constructed by the same grammar but with different letters) with those in a control condition. Predictors were identical in both conditions—judgements of control participants were treated as if they were based on knowledge gained in a standard training stage. The results of this experiment as well as reanalyses of a former study support the usefulness of our approach.     

语音短时记忆与词汇知识对第二语言词汇学习的影响

选取两种语音熟悉程度不同的非词为实验材料,把语音短时记忆区分为项目短时记忆和序列短时记忆,考察语音短时记忆与词汇知识对汉英双语者第二语言（英语）词汇学习的影响。实验1采用产出性的方式进行学习,结果发现,词汇知识与项目短时记忆对语音熟悉非词的学习起预测作用;词汇知识与序列短时记忆对语音不熟悉非词学习起预测作用。实验2采用接受性的方式进行学习,结果发现,项目短时记忆、序列短时记忆和词汇知识都对语音熟悉非词学习起独立的预测作用;项目短时记忆和序列短时记忆对语音不熟悉非词学习起独立的预测作用。实验结果表明,语音短时记忆和词汇知识都是影响英语词汇学习的重要因素。具体而言,学习语音熟悉的词汇,词汇知识起着更为重要的作用;学习语音不熟悉的词汇,语音短时记忆、特别是序列短时记忆起着更为重要的作用,而且两者作用的大小随着词汇学习方式的不同而发生变化。