Publications

Abstract

Language processing is rapidly incremental, but evidence bearing upon this assumption comes from very few languages. In this paper we report on a study of incremental processing in Murrinhpatha, a polysynthetic Australian language, which expresses complex sentence-level meanings in a single verb, the full meaning of which is not clear until the final morph. Forty native Murrinhpatha speakers participated in a visual world eyetracking experiment in which they viewed two complex scenes as they heard a verb describing one of the scenes. The scenes were selected so that the verb describing the target scene had either no overlap with a possible description of the competitor image, or overlapped from the start (onset overlap) or at the end of the verb (rhyme overlap). The results showed that, despite meaning only being clear at the end of the verb, Murrinhpatha speakers made incremental predictions that differed across conditions. The findings demonstrate that processing in polysynthetic languages is rapid and incremental, yet unlike in commonly studied languages like English, speakers make parsing predictions based on information associated with bound morphs rather than discrete words.

Abstract

A long-standing question in language development concerns the nature of the relationship between early lexical and grammatical knowledge. The very strong correlation between the two has led some to argue that lexical and grammatical knowledge may be inseparable, consistent with psycholinguistic theories that eschew a distinction between the two systems. However, little research has explicitly examined whether early lexical and grammatical knowledge are statistically separable. Moreover, there are two under-appreciated methodological challenges in such research. First, the relationship between lexical and grammatical knowledge may change during development. Second, non-linear mappings between true and observed scores on scales of lexical and grammatical knowledge could lead to spurious multidimensionality. In the present study, we overcome these challenges by using vocabulary and grammar data from several developmental time points and a statistical method robust to such non-linear mappings. In Study 1, we examined item-level vocabulary and grammar data from two American English samples from a large online repository of data from studies employing a commonly used language development scale. We found clear evidence that vocabulary and grammar were separable by two years of age. In Study 2, we combined data from two longitudinal studies of language acquisition that used the same scale (at 18/19, 21, 24 and 30 months) and found evidence that vocabulary and grammar were, under some conditions, separable by 18 months. Results indicate that, while there is clearly a very strong relationship between vocabulary and grammar knowledge in early language development, the two are separable. Implications for the mechanisms underlying language development are discussed.

Abstract

Continuous vector word representations (or
word embeddings) have shown success in cap-turing semantic relations between words, as evidenced by evaluation against behavioral data of adult performance on semantic tasks (Pereira et al., 2016). Adult semantic knowl-edge is the endpoint of a language acquisition process; thus, a relevant question is whether these models can also capture emerging word
representations of young language learners. However, the data for children’s semantic knowledge across development is scarce. In this paper, we propose to bridge this gap by using Age of Acquisition norms to evaluate word embeddings learnt from child-directed input. We present two methods that evaluate word embeddings in terms of (a) the semantic neighbourhood density of learnt words, and (b) con-
vergence to adult word associations. We apply our methods to bag-of-words models, and find that (1) children acquire words with fewer semantic neighbours earlier, and (2) young learners only attend to very local context. These findings provide converging evidence for validity of our methods in understanding the prerequisite features for a distributional model of word learning.

Abstract

Research on infants’ online lexical processing by Fernald, Perfors, and Marchman (2006) revealed substantial individual differences that are related to vocabulary development, such that infants with better lexical processing efficiency show greater vocabulary growth across time. Although it is clear that individual differences in lexical processing efficiency exist and are meaningful, the theoretical nature of lexical processing efficiency and its relation to vocabulary size is less clear. In the current study, we asked two questions: (a) Is lexical processing efficiency better conceptualized as a central processing capacity or as an emergent capacity reflecting a collection of word-specific capacities? and (b) Is there evidence for a causal role for lexical processing efficiency in early vocabulary development? In the study, 120 infants were tested on a measure of lexical processing at 18, 21, and 24 months, and their vocabulary was measured via parent report. Structural equation modeling of the 18-month time point data revealed that both theoretical constructs represented in the first question above (a) fit the data. A set of regression analyses on the longitudinal data revealed little evidence for a causal effect of lexical processing on vocabulary but revealed a significant effect of vocabulary size on lexical processing efficiency early in development. Overall, the results suggest that lexical processing efficiency is a stable construct in infancy that may reflect the structure of the developing lexicon.

Abstract

We report on two experiments that investigated the acquisition of the Tagalog symmetrical voice system, a typologically rare feature of Western Austronesian languages in which there are more than one basic transitive construction and no preference for agents to be syntactic subjects. In the experiments, 3-, 5-, and 7-year-old Tagalog-speaking children and adults completed a structural priming task that manipulated voice and word order, with the uniqueness of Tagalog allowing us to tease apart priming of thematic role order from that of syntactic roles. Participants heard a description of a picture showing a transitive action, and were then asked to complete a sentence of an unrelated picture using a voice-marked verb provided by the experimenter. Our results show that children gradually acquire an agent-before-patient preference, instead of having a default mapping of the agent to the first noun position. We also found an earlier mastery of the patient voice verbal and nominal marker configuration (patient is the subject), suggesting that children do not initially map the agent to the subject. Children were primed by thematic role but not syntactic role order, suggesting that they prioritize mapping of the thematic roles to sentence positions.

Abstract

Humans associate abstract words with physical stimulus dimensions, such as linking upward locations with positive concepts (e.g., happy = up). These associations manifest both via subjective reports of associations and on objective performance metrics. Humans also report subjective associations between colours and abstract words (e.g., joy is linked to yellow). Here we tested whether such associations manifest on objective task performance, even when not task-relevant. Across three experiments, participants were presented with abstract words in physical colours that were either congruent with previously-reported subjective word-colour associations (e.g., victory in red and unhappy in blue), or were incongruent (e.g., victory in blue and unhappy in red). In Experiment 1, participants' task was to identify the valence of words. This congruency manipulation systematically affected objective task performance. In Experiment 2, participants completed two blocks, a valence-identification and a colour-identification task block. Both tasks produced congruency effects on performance, however, the results of the colour identification block could have reflected learning effects (i.e., associating the more common congruent colour with the word). This issue was rectified in Experiment 3, whereby participants completed the same two tasks as Experiment 2, but now matched congruent and incongruent pairs were used for both tasks. Again, both tasks produced reliable congruency effects. Item analyses in each experiment revealed that these effects demonstrated a degree of item specificity. Overall, there was clear evidence that at least some abstract word-colour pairings can systematically affect behaviour.

Abstract

The computations involved in statistical learning have long been debated. Here, we build on work suggesting that a basic memory process, chunking , may account for the processing of statistical regularities into larger units. Drawing on methods from the memory literature, we developed a novel paradigm to test statistical learning by leveraging a robust phenomenon observed in serial recall tasks: that short‐term memory is fundamentally shaped by long‐term distributional learning. In the statistically induced chunking recall (SICR) task, participants are exposed to an artificial language, using a standard statistical learning exposure phase. Afterward, they recall strings of syllables that either follow the statistics of the artificial language or comprise the same syllables presented in a random order. We hypothesized that if individuals had chunked the artificial language into word‐like units, then the statistically structured items would be more accurately recalled relative to the random controls. Our results demonstrate that SICR effectively captures learning in both the auditory and visual modalities, with participants displaying significantly improved recall of the statistically structured items, and even recall specific trigram chunks from the input. SICR also exhibits greater test–retest reliability in the auditory modality and sensitivity to individual differences in both modalities than the standard two‐alternative forced‐choice task. These results thereby provide key empirical support to the chunking account of statistical learning and contribute a valuable new tool to the literature.

Abstract

Humans vary in almost every dimension imaginable, and language is no
exception. In this article, we review the past research that has focused on
individual differences (IDs) in first language acquisition. We first consider
how different theoretical traditions in language acquisition treat IDs, and
we argue that a focus on IDs is important given its potential to reveal the
developmental dynamics and architectural constraints of the linguistic system.
We then review IDs research that has examined variation in children’s
linguistic input, early speech perception, and vocabulary and grammatical
development. In each case, we observe systematic and meaningful variation,
such that variation in one domain (e.g., early auditory and speech
processing) has meaningful developmental consequences for development
in higher-order domains (e.g., vocabulary). The research suggests a high
degree of integration across the linguistic system, in which development
across multiple linguistic domains is tightly coupled.

Abstract

Statistical learning (SL) has been a prominent focus of research in developmental and adult populations, guided by the assumption that it is a fundamental component of learning underlying higher-order cognition. In developmental populations, however, there have been recent concerns regarding the degree to which many current tasks reliably measure SL, particularly in younger children. In the current article, we present the results of two studies that measured auditory statistical learning (ASL) of linguistic stimuli in children aged 5–8 years. Children listened to 6 min of continuous syllables comprising four trisyllabic pseudowords. Following the familiarization phase, children completed (a) a two-alternative forced-choice task and (b) a serial recall task in which they repeated either target sequences embedded during familiarization or foils, manipulated for sequence length. Results showed that, although both measures consistently revealed learning at the group level, the recall task better captured learning across the full range of abilities and was more reliable at the individual level. We conclude that, as has also been demonstrated in adults, the method holds promise for future studies of individual differences in ASL of linguistic stimuli.

Abstract

Much of Lieven’s pioneering work has helped move the study of individual differences to the centre of child language research. The goal of the present chapter is to illustrate how the study of individual differences provides crucial insights into the language acquisition process. In part one, we summarise some of the evidence showing how pervasive individual differences are across the whole of the language system; from gestures to morphosyntax. In part two, we describe three causal factors implicated in explaining individual differences, which, we argue, must be built into any theory of language acquisition (intrinsic differences in the neurocognitive learning mechanisms, the child’s communicative environment, and developmental cascades in which each new linguistic skill that the child has to acquire depends critically on the prior acquisition of foundational abilities). In part three, we present an example study on the role of the speed of linguistic processing on vocabulary development, which illustrates our approach to individual differences. The results show evidence of a changing relationship between lexical processing speed and vocabulary over developmental time, perhaps as a result of the changing nature of the structure of the lexicon. The study thus highlights the benefits of an individual differences approach in building, testing, and constraining theories of language acquisition.

Abstract

A core question in language acquisition is whether children’s syntactic processing is experience-dependent and language-specific, or whether it is governed by abstract, universal syntactic machinery. We address this question by presenting corpus and on-line processing dat a from children learning Mandarin Chinese, a language that has been important in debates about the universality of parsing processes. The corpus data revealed that two different relative clause constructions in Mandarin are differentially used to modify syntactic subjects and objects. In the experiment, 4-year-old children’s eye-movements were recorded as they listened to the two RC construction types (e.g., Can you pick up the pig that pushed the sheep?). A permutation analysis showed that children’s ease of comprehension was closely aligned with the distributional frequencies, suggesting syntactic processing preferences are shaped by the input experience of these constructions.