Disentangling the Role of Biphone Probability From Neighborhood Density in the Perception of Nonwords.

In six experiments we explored how biphone probability and lexical neighborhood density influence listeners' categorization of vowels embedded in nonword sequences. We found independent effects of each. Listeners shifted categorization of a phonetic continuum to create a higher probability sequence, even when neighborhood density was controlled. Similarly, listeners shifted categorization to create a nonword from a denser neighborhood, even when biphone probability was controlled. Next, using a visual world eye-tracking task, we determined that biphone probability information is used rapidly by listeners in perception. In contrast, task complexity and irrelevant variability in the stimuli interfere with neighborhood density effects. These results support a model in which both biphone probability and neighborhood density independently affect word recognition, but only biphone probability effects are observed early in processing.

Sensitivity to syllable stress regularities in externally but not self-triggered speech in Dutch.

Several theories of predictive processing propose reduced sensory and neural responses to anticipated events. Support comes from magnetoencephalography/electroencephalography (M/EEG) studies, showing reduced auditory N1 and P2 responses to self-generated compared to externally generated events, or when the timing and form of stimuli are more predictable. The current study examined the sensitivity of N1 and P2 responses to statistical speech regularities. We employed a motor-to-auditory paradigm comparing event-related potential (ERP) responses to externally and self-triggered pseudowords. Participants were presented with a cue indicating which button to press (motor-auditory condition) or which pseudoword would be presented (auditory-only condition). Stimuli consisted of the participant's own voice uttering pseudowords that varied in phonotactic probability and syllable stress. We expected to see N1 and P2 suppression for self-triggered stimuli, with greater suppression effects for more predictable features such as high phonotactic probability and first-syllable stress in pseudowords. In a temporal principal component analysis (PCA), we observed an interaction between syllable stress and condition for the N1, where second-syllable stress items elicited a larger N1 than first-syllable stress items, but only for externally generated stimuli. We further observed an effect of syllable stress on the P2, where first-syllable stress items elicited a larger P2. Strikingly, we did not observe motor-induced suppression for self-triggered stimuli for either the N1 or P2 component, likely due to the temporal predictability of the stimulus onset in both conditions. Taking into account previous findings, the current results suggest that sensitivity to syllable stress regularities depends on task demands.

Combining statistics: the role of phonotactics on cross-situational word learning.

Language learners can rely on phonological and semantic information to learn novel words. Using a cross-situational word learning paradigm, we explored the role of phonotactic probabilities on word learning in ambiguous contexts. Brazilian-Portuguese speaking adults (N = 30) were exposed to two sets of word-object pairs. Words from one set of labels had slightly higher phonotactic probabilities than words from the other set. By tracking co-occurrences of words and objects, participants were able to learn word-object mappings similarly across both sets. Our findings contrast with studies showing a facilitative effect of phonotactic probability on word learning in non-ambiguous contexts.

The differential roles of lexical and sublexical processing during spoken-word recognition in clear and in noise.

Successful spoken-word recognition relies on interplay between lexical and sublexical processing. Previous research demonstrated that listeners readily shift between more lexically-biased and more sublexically-biased modes of processing in response to the situational context in which language comprehension takes place. Recognizing words in the presence of background noise reduces the perceptual evidence for the speech signal and - compared to the clear - results in greater uncertainty. It has been proposed that, when dealing with greater uncertainty, listeners rely more strongly on sublexical processing. The present study tested this proposal using behavioral and electroencephalography (EEG) measures. We reasoned that such an adjustment would be reflected in changes in the effects of variables predicting recognition performance with loci at lexical and sublexical levels, respectively. We presented native speakers of Dutch with words featuring substantial variability in (1) word frequency (locus at lexical level), (2) phonological neighborhood density (loci at lexical and sublexical levels) and (3) phonotactic probability (locus at sublexical level). Each participant heard each word in noise (presented at one of three signal-to-noise ratios) and in the clear and performed a two-stage lexical decision and transcription task while EEG was recorded. Using linear mixed-effects analyses, we observed behavioral evidence that listeners relied more strongly on sublexical processing when speech quality decreased. Mixed-effects modelling of the EEG signal in the clear condition showed that sublexical effects were reflected in early modulations of ERP components (e.g., within the first 300 msec post word onset). In noise, EEG effects occurred later and involved multiple regions activated in parallel. Taken together, we found evidence - especially in the behavioral data - supporting previous accounts that the presence of background noise induces a stronger reliance on sublexical processing.

Combining statistics: the role of phonotactics on cross-situational word learning

Abstract Language learners can rely on phonological and semantic information to learn novel words. Using a cross-situational word learning paradigm, we explored the role of phonotactic probabilities on word learning in ambiguous contexts. Brazilian-Portuguese speaking adults (N = 30) were exposed to two sets of word-object pairs. Words from one set of labels had slightly higher phonotactic probabilities than words from the other set. By tracking co-occurrences of words and objects, participants were able to learn word-object mappings similarly across both sets. Our findings contrast with studies showing a facilitative effect of phonotactic probability on word learning in non-ambiguous contexts.

Nonword repetition depends on the frequency of sublexical representations at different grain sizes: Evidence from a multi-factorial analysis.

The nonword repetition task (NWR) has been widely used in basic cognitive and clinical research, as well as in clinical assessment, and has been proposed as a clinical marker for Specific Language Impairment (SLI). Yet the mechanisms underlying performance on this task are not clear. This study offers insights into these mechanisms through a comprehensive examination of item-related variables identified in previous research as possibly contributing to NWR scores and through testing the predictive power of each in relation to the others. A unique feature of the study is that all factors are considered simultaneously. Fifty-seven typically developing children were tested with a NWR task containing 150 nonwords differing in length, phonotactic probability, lexical neighbourhood and phonological complexity. The results indicate that phonological processing of novel words draws on sublexical representations at all grain sizes and that these representations are phonological, unstructured and insensitive to morphemehood. We propose a novel index - mean ngram frequency of all phonemes - that best captures the extent to which a nonword draws on sublexical representations. The study demonstrates the primacy of sublexical representations in NWR performance with implications for the nature of the deficit in SLI.

A Web-based interface to calculate phonotactic probability for words and nonwords in Modern Standard Arabic.

A number of databases (Storkel Behavior Research Methods, 45, 1159-1167, 2013) and online calculators (Vitevitch & Luce Behavior Research Methods, Instruments, and Computers, 36, 481-487, 2004) have been developed to provide statistical information about various aspects of language, and these have proven to be invaluable assets to researchers, clinicians, and instructors in the language sciences. The number of such resources for English is quite large and continues to grow, whereas the number of such resources for other languages is much smaller. This article describes the development of a Web-based interface to calculate phonotactic probability in Modern Standard Arabic (MSA). A full description of how the calculator can be used is provided. It can be freely accessed at http://phonotactic.drupal.ku.edu/ .

Effects of Vocabulary and Phonotactic Probability on 2-Year-Olds' Nonword Repetition.

This study investigates the relationship between nonword repetition (NWR) and vocabulary in 2-year-olds. Questions addressed are whether (1) NWR and vocabulary are associated, (2) phonotactic probability affects NWR, and (3) there is an interaction effect between phonotactic probability and vocabulary on NWR performance. The general aim of the study is to investigate whether NWR, as a task of phonological storage, assesses the quality of phonological representations in children as young as 2 years of age. 557 Dutch 2-year-olds performed a NWR task containing items of varying phonotactic probability as well as a receptive vocabulary task. The results showed a moderate, significant correlation between NWR and vocabulary. Phonotactic probability had an effect on NWR performance. Further analyses showed that there was a significant interaction between phonotactic probability and vocabulary for part of the items. These results support previously reported effects of vocabulary and phonotactic probability on NWR in older, English-speaking children for a large sample of Dutch-speaking 2-year-olds, and provide evidence that NWR assesses the quality of phonological representations already in very young children.

The influence of phonotactic probability and neighborhood density on children's production of newly learned words.

A word learning paradigm was used to teach children novel words that varied in phonotactic probability and neighborhood density. The effects of frequency and density on speech production were examined when phonetic forms were non-referential (i.e., when no referent was attached) and when phonetic forms were referential (i.e., when a referent was attached through fast mapping). Two methods of analysis were included: (1) kinematic variability of speech movement patterning; and (2) measures of segmental accuracy. Results showed that phonotactic frequency influenced the stability of movement patterning whereas neighborhood density influenced phoneme accuracy. Motor learning was observed in both non-referential and referential novel words. Forms with low phonotactic probability and low neighborhood density showed a word learning effect when a referent was assigned during fast mapping. These results elaborate on and specify the nature of interactivity observed across lexical, phonological, and articulatory domains.

Nonword repetition errors of children with and without specific language impairments (SLI).

BACKGROUND: Two ubiquitous findings from the literature are that (1) children with specific language impairments (SLI) repeat nonwords less accurately than peers with typical language development (TLD), and (2) all children repeat nonwords with frequent phonotactic patterns more accurately than low-probability nonwords. Many studies have examined repetition accuracy, but little work has examined children's errors. AIMS: To examine nonword repetition errors from a previously published study in terms of phonotactic probability. METHODS & PROCEDURES: Eighteen children with SLI (mean age = 9;2) and 18 age-matched controls (mean age = 8;11) repeated three- and four-syllable nonwords. Substitutions were analysed in terms of phoneme frequency and phonotactic probability of the syllable containing the substitution. OUTCOMES & RESULTS: Results for all children show that phoneme substitutions generally involved replacement with more frequently occurring phonemes. Also, the resulting phonotactic probability within syllables containing substitutions was greater than the probability of the targets. This trend did not differ by group. CONCLUSIONS & IMPLICATIONS: These results suggest that both children with SLI and children with TLD substitute less frequent phonemes with more frequent ones, and less probabilistic syllables with higher probability ones.

Early effects of neighborhood density and phonotactic probability of spoken words on event-related potentials.

All current models of spoken word recognition propose that sound-based representations of spoken words compete with, or inhibit, one another during recognition. In addition, certain models propose that higher probability sublexical units facilitate recognition under certain circumstances. Two experiments were conducted examining ERPs to spoken words and nonwords simultaneously varying in phonotactic probability and neighborhood density. Results showed that the amplitude of the P2 potential was greater for high probability-density words and nonwords, suggesting an early inhibitory effect of neighborhood density. In order to closely examine the role of phonotactic probability, effects of initial phoneme frequency were also examined. The latency of the P2 potential was shorter for words with high initial-consonant probability, suggesting a facilitative effect of phonotactic probability. The current results are consistent with findings from previous studies using reaction time and eye-tracking paradigms and provide new insights into the time-course of lexical and sublexical activation and competition.

Developmental change is key to understanding primary language impairment: the case of phonotactic probability and nonword repetition.

PURPOSE: In this study, the authors aimed to explore the relationship between lexical and phonological knowledge in children with primary language impairment (PLI) through the application of a developmental methodology. Specifically, they tested whether there is evidence for an impairment in the process of phonological abstraction in this group of children over and above that which would be predicted by their vocabulary growth. METHOD: The authors measured developmental change in the abilities of typically developing (TD) children ( n = 38, chronological age [CA] = 3;0-5;6 [years;months]) and those with PLI ( n = 13, CA = 3;0-6;6 and 4;6-8;0) to repeat nonwords with high and low phonotactic probability (PP) to uncover group differences in the process of abstraction of phonological representations. RESULTS: Cross-sectional developmental trajectories of change in nonword repetition abilities were compared across CA and vocabulary growth. Unlike TD children, the children with PLI did not evince a narrowing gap in the influence of PP across development, and they reached a plateau in their development. CONCLUSION: These results suggest slowed emergence of phonological representations in PLI, with a plateau in the development of lexical-phonological representations. This plateau may represent entrenchment and "fixing" due to a missed critical period and/or atypical word learning biases in PLI.

Factors that influence fast mapping in children exposed to Spanish and English.

PURPOSE: The purpose of this study was to determine whether children exposed to 2 languages would benefit from the phonotactic probability cues of a single language in the same way as monolingual peers and to determine whether crosslinguistic influence would be present in a fast-mapping task. METHOD: Two groups of typically developing children (monolingual English and bilingual Spanish-English) took part in a computer-based fast-mapping task that manipulated phonotactic probability. Children were preschool-aged (N = 50) or school-aged (N = 34). Fast mapping was assessed through name-identification and naming tasks. Data were analyzed using mixed analyses of variance with post hoc testing and simple regression. RESULTS: Bilingual and monolingual preschoolers showed sensitivity to English phonotactic cues in both tasks, but bilingual preschoolers were less accurate than monolingual peers in the naming task. School-aged bilingual children had nearly identical performance to monolingual peers. CONCLUSION: Knowing that children exposed to two languages can benefit from the statistical cues of a single language can help inform ideas about instruction and assessment for bilingual learners.

The effect of incremental changes in phonotactic probability and neighborhood density on word learning by preschool children.

PURPOSE: Phonotactic probability or neighborhood density has predominately been defined through the use of gross distinctions (i.e., low vs. high). In the current studies, the authors examined the influence of finer changes in probability (Experiment 1) and density (Experiment 2) on word learning. METHOD: The authors examined the full range of probability or density by sampling 5 nonwords from each of 4 quartiles. Three- and 5-year-old children received training on nonword-nonobject pairs. Learning was measured in a picture-naming task immediately following training and 1 week after training. Results were analyzed through the use of multilevel modeling. RESULTS: A linear spline model best captured nonlinearities in phonotactic probability. Specifically, word learning improved as probability increased in the lowest quartile, worsened as probability increased in the mid-low quartile, and then remained stable and poor in the 2 highest quartiles. An ordinary linear model sufficiently described neighborhood density. Here, word learning improved as density increased across all quartiles. CONCLUSION: Given these different patterns, phonotactic probability and neighborhood density appear to influence different word learning processes. Specifically, phonotactic probability may affect recognition that a sound sequence is an acceptable word in the language and is a novel word for the child, whereas neighborhood density may influence creation of a new representation in long-term memory.