Heeding the voice of experience: the role of talker variation in lexical access

Two experiments used the head-mounted eye-tracking methodology to examine the time course of lexical activation in the face of a non-phonemic cue, talker variation. We found that lexical competition was attenuated by consistent talker differences between words that would otherwise be lexical competitors. In Experiment 1, some English cohort word-pairs were consistently spoken by a single talker (male couch, male cows), while other word-pairs were spoken by different talkers (male sheep, female sheet). After repeated instances of talker-word pairings, words from different-talker pairs showed smaller proportions of competitor fixations than words from same-talker pairs. In Experiment 2, participants learned to identify black-and-white shapes from novel labels spoken by one of two talkers. All of the 16 novel labels were VCVCV word-forms atypical of, but not phonologically illegal in, English. Again, a word was consistently spoken by one talker, and its cohort or rhyme competitor was consistently spoken either by that same talker (same-talker competitor) or the other talker (different-talker competitor). Targets with different-talker cohorts received greater fixation proportions than targets with same-talker cohorts, while the reverse was true for fixations to cohort competitors; there were fewer erroneous selections of competitor referents for different-talker competitors than same-talker competitors. Overall, these results support a view of the lexicon in which entries contain extra-phonemic information. Extensions of the artificial lexicon paradigm and developmental implications are discussed.     

Effects of language experience on the perception of American Sign Language

Perception of American Sign Language (ASL) handshape and place of articulation parameters was investigated in three groups of signers: deaf native signers, deaf non-native signers who acquired ASL between the ages of 10 and 18, and hearing non-native signers who acquired ASL as a second language between the ages of 10 and 26. Participants were asked to identify and discriminate dynamic synthetic signs on forced choice identification and similarity judgement tasks. No differences were found in identification performance, but there were effects of language experience on discrimination of the handshape stimuli. Participants were significantly less likely to discriminate handshape stimuli drawn from the region of the category prototype than stimuli that were peripheral to the category or that straddled a category boundary. This pattern was significant for both groups of deaf signers, but was more pronounced for the native signers. The hearing L2 signers exhibited a similar pattern of discrimination, but results did not reach significance. An effect of category structure on the discrimination of place of articulation stimuli was also found, but it did not interact with language background. We conclude that early experience with a signed language magnifies the influence of category prototypes on the perceptual processing of handshape primes, leading to differences in the distribution of attentional resources between native and non-native signers during language comprehension.     

The link between statistical segmentation and word learning in adults

Many studies have shown that listeners can segment words from running speech based on conditional probabilities of syllable transitions, suggesting that this statistical learning could be a foundational component of language learning. However, few studies have shown a direct link between statistical segmentation and word learning. We examined this possible link in adults by following a statistical segmentation exposure phase with an artificial lexicon learning phase. Participants were able to learn all novel object-label pairings, but pairings were learned faster when labels contained high probability (word-like) or non-occurring syllable transitions from the statistical segmentation phase than when they contained low probability (boundary-straddling) syllable transitions. This suggests that, for adults, labels inconsistent with expectations based on statistical learning are harder to learn than consistent or neutral labels. In contrast, a previous study found that infants learn consistent labels, but not inconsistent or neutral labels.     

Meaning matters in children's plural productions

The English plural is about the number of individuals in a set of like kinds. Two-year-old children use the plural but do not do so in all obligatory contexts. The present report asks whether the limitations on their production of the plural are related to aspects of meaning. In two Experiments plural productions were elicited from 2-year-old children for sets of size two and four and for instances of basic-level categories that were either similar or identical. Children were much more likely to produce the plural of these well-known nouns when there were four rather than two and when the instances were identical rather than merely similar. The results provide new evidence on children's acquisition of the English plural, showing that children's early productions are not just limited by knowledge of the noun and its plural form but also is limited by properties of the labeled sets in ways that are relevant to the underlying meaning of the plural.     

On the role of regular phonological variation in lexical access: evidence from voice assimilation in French

The present study investigated whether lexical access is affected by a regular phonological variation in connected speech: voice assimilation in French. Two associative priming experiments were conducted to determine whether strongly assimilated, potentially ambiguous word forms activate the conceptual representation of the underlying word. Would the ambiguous word form [sud] (either assimilated soute 'hold' or soude 'soda') facilitate "bagage" 'luggage', which is semantically related to soute but not to soude? In Experiment 1, words in either canonical or strongly assimilated form were presented as primes. Both forms primed their related target to the same extent. Potential lexical ambiguity did not modulate priming effects. In Experiment 2, the primes such as assimilated soute pronounced [sud] used in Experiment 1 were replaced with primes such as soude canonically pronounced [sud]. No semantic priming effect was obtained with these primes. Therefore, the effect observed for assimilated forms in Experiment 1 cannot be due to overall phonological proximity between canonical and assimilated forms. We propose that listeners must recover the intended words behind the assimilated forms through the exploitation of the remaining traces of the underlying form, however subtle these traces may be.     

A computational model of early argument structure acquisition

How children go about learning the general regularities that govern language, as well as keeping track of the exceptions to them, remains one of the challenging open questions in the cognitive science of language. Computational modeling is an important methodology in research aimed at addressing this issue. We must determine appropriate learning mechanisms that can grasp generalizations from examples of specific usages, and that exhibit patterns of behavior over the course of learning similar to those in children. Early learning of verb argument structure is an area of language acquisition that provides an interesting testbed for such approaches due to the complexity of verb usages. A range of linguistic factors interact in determining the felicitous use of a verb in various constructions —associations between syntactic forms and properties of meaning that form the basis for a number of linguistic and psycholinguistic theories of language. This article presents a computational model for the representation, acquisition, and use of verbs and constructions. The Bayesian framework is founded on a novel view of constructions as a probabilistic association between syntactic and semantic features. The computational experiments reported here demonstrate the feasibility of learning general constructions, and their exceptions, from individual usages of verbs. The behavior of the model over the timecourse of acquisition mimics, in relevant aspects, the stages of learning exhibited by children. Therefore, this proposal sheds light on the possible mechanisms at work in forming linguistic generalizations and maintaining knowledge of exceptions.     

Effects of Attention on the Strength of Lexical Influences on Speech Perception: Behavioral Experiments and Computational Mechanisms

The effects of lexical context on phonological processing are pervasive and there have been indications that such effects may be modulated by attention. However, attentional modulation in speech processing is neither well documented nor well understood. Experiment 1 demonstrated attentional modulation of lexical facilitation of speech sound recognition when task and critical stimuli were identical across attention conditions. We propose modulation of lexical activation as a neurophysiologically plausible computational mechanism that can account for this type of modulation. Contrary to the claims of critics, this mechanism can account for attentional modulation without violating the principle of interactive processing. Simulations of the interactive TRACE model extended to include two different ways of modulating lexical activation showed that each can account for attentional modulation of lexical feedback effects. Experiment 2 tested conflicting predictions from the two implementations and provided evidence that is consistent with bias input as the mechanism of attentional control of lexical activation.     

Autonomous construction of ecologically and socially relevant semantics

This article presents a synthetic modeling approach to the problem of grounded construction of concepts. In many computational models of grounded language acquisition and evolution, meanings are created in the process of discrimination between a chosen object and other objects present on the scene of communication. We argue that categories constructed for the purpose of identification rather than discrimination are more suitable for the detached language use (talking about things not present here and now). We describe a semantics based on so-called identification criteria constructed by extracting cross-situational similarities among instances of a category, and present several computational models. In the model of individual category construction, the instances are grouped to categories by common motor programs (affordances), while in the model of social learning, focused on the influence of naming on category formation, entities are considered members of the same category, if they are labeled with the same word by an external teacher. By these two mechanisms, the learner can construct interactionally grounded representation of objects, properties, relations, changes, complex situations and events. We also report and analyze simulation results of an experiment focused on the dynamics of meanings in iterated intergenerational transmission.     

Automatic evaluation of syntactic learners in typologically-different languages

Human syntax acquisition involves a system that can learn constraints on possible word sequences in typologically-different human languages. Evaluation of computational syntax acquisition systems typically involves theory-specific or language-specific assumptions that make it difficult to compare results in multiple languages. To address this problem, a bag-of-words incremental generation (BIG) task with an automatic sentence prediction accuracy (SPA) evaluation measure was developed. The BIG–SPA task was used to test several learners that incorporated n-gram statistics which are commonly found in statistical approaches to syntax acquisition. In addition, a novel Adjacency–Prominence learner, that was based on psycholinguistic work in sentence production and syntax acquisition, was also tested and it was found that this learner yielded the best results in this task on these languages. In general, the BIG–SPA task is argued to be a useful platform for comparing explicit theories of syntax acquisition in multiple languages.