A meta-analysis of infants' word-form recognition.

Recognizing word forms is an important step on infants' way toward mastering their native language. The present study takes a meta-analytic approach to assess overarching questions on the literature of early word-form recognition. Specifically, we investigated the extent to which there is cross-linguistic evidence for an early recognition lexicon, and how it may be influenced by infant age, language background, and familiarity of the selected stimuli (approximated by parent-reported word knowledge). Our meta-analysis-with open data access on metalab.stanford.edu-was based on 32 experiments in 16 different published or unpublished studies on infants 5-15 months of age. We found an overall significant effect of word-form familiarity on infants' responses. This effect increased with age and was higher for infants learning Romance languages than other languages. We further found that younger, but not older, infants showed higher effect sizes for more familiar word lists. These insights should help researchers plan future studies on word-form recognition.

Dual language input and the impact of language separation on early lexical development.

We examined properties of the input and the environment that characterize bilingual exposure in 11-month-old infants with a regular exposure to French and an additional language, and their possible effects on receptive vocabulary size. Using a diary method, we found that a majority of the families roughly followed a one-parent-one-language approach. Yet, the two languages co-occurred to various extents within the same half-hour both within and across speakers. We used exploratory correlation analyses to examine potential effects of the dual input on the size of infants' vocabularies. The results revealed some evidence for an impact of language separation by speakers.

Perceptual deletion and asymmetric lexical access in second language learners.

French listeners have difficulty perceiving /h/, and as L2 speakers they frequently omit /h/ in English words. This study investigated their processing of English /h/-initial words. Participants performed a lexical decision task on words and nonwords, where the nonwords were created from /h/-initial and vowel-initial words by removing or adding /h/, respectively. The results mirrored the production pattern, with more misses on /h/-initial words (e.g., holiday) and more false alarms on vowel-initial nonwords (e.g., usband). These results are interpreted in light of previous research on asymmetries in L2 lexical access.

Symbouki: a meta-analysis on the emergence of sound symbolism in early language acquisition.

Adults and toddlers systematically associate pseudowords such as "bouba" and "kiki" with round and spiky shapes, respectively, a sound symbolic phenomenon known as the "bouba-kiki effect". To date, whether this sound symbolic effect is a property of the infant brain present at birth or is a learned aspect of language perception remains unknown. Yet, solving this question is fundamental for our understanding of early language acquisition. Indeed, an early sensitivity to such sound symbolic associations could provide a powerful mechanism for language learning, playing a bootstrapping role in the establishment of novel sound-meaning associations. The aim of the present meta-analysis (SymBouKi) is to provide a quantitative overview of the emergence of the bouba-kiki effect in infancy and early childhood. It allows a high-powered assessment of the true sound symbolic effect size by pooling over the entire set of 11 extant studies (six published, five unpublished), entailing data from 425 participants between 4 and 38 months of age. The quantitative data provide statistical support for a moderate, but significant, sound symbolic effect. Further analysis found a greater sensitivity to sound symbolism for bouba-type pseudowords (i.e., round sound-shape correspondences) than for kiki-type pseudowords (i.e., spiky sound-shape correspondences). For the kiki-type pseudowords, the effect emerged with age. Such discrepancy challenges the view that sensitivity to sound symbolism is an innate language mechanism rooted in an exuberant interconnected brain. We propose alternative hypotheses where both innate and learned mechanisms are at play in the emergence of sensitivity to sound symbolic relationships.

Which epenthetic vowel? Phonetic categories versus acoustic detail in perceptual vowel epenthesis.

This study aims to quantify the relative contributions of phonetic categories and acoustic detail on phonotactically induced perceptual vowel epenthesis in Japanese listeners. A vowel identification task tested whether a vowel was perceived within illegal consonant clusters and, if so, which vowel was heard. Cross-spliced stimuli were used in which vowel coarticulation present in the cluster did not match the quality of the flanking vowel. Two clusters were used, /hp/ and /kp/, the former containing larger amounts of resonances of the preceding vowel. While both flanking vowel and coarticulation influenced vowel quality, the influence of coarticulation was larger, especially for /hp/.

How the demographic makeup of our community influences speech perception.

Speech perception is known to be influenced by listeners' expectations of the speaker. This paper tests whether the demographic makeup of individuals' communities can influence their perception of foreign sounds by influencing their expectations of the language. Using online experiments with participants from all across the U.S. and matched census data on the proportion of Spanish and other foreign language speakers in participants' communities, this paper shows that the demographic makeup of individuals' communities influences their expectations of foreign languages to have an alveolar trill versus a tap (Experiment 1), as well as their consequent perception of these sounds (Experiment 2). Thus, the paper shows that while individuals' expectations of foreign language to have a trill occasionally lead them to misperceive a tap in a foreign language as a trill, a higher proportion of non-trill language speakers in one's community decreases this likelihood. These results show that individuals' environment can influence their perception by shaping their linguistic expectations.

Asymmetries in the exploitation of phonetic features for word recognition.

French listeners' reliance on voicing, manner, and place was tested in a mispronunciation detection task. Mispronounced words were more likely to be recognized when the mispronunciation concerned voicing rather than manner or place. This indicates that listeners rely less on the former than on the latter for the purposes of word recognition. Further, the role of visual cues to phonetic features was explored by the task being conducted in both an audio-only and an audiovisual version, but no effect of modality was found. Discussion focuses on crosslinguistic comparisons and lexical factors that might influence the weight of individual features.

Consonants are More Important than Vowels in the Bouba-kiki Effect.

Adult listeners systematically associate certain speech sounds with round or spiky shapes, a sound-symbolic phenomenon known as the "bouba-kiki effect." In this study, we investigate the respective influences of consonants and vowels in this phenomenon. French participants were asked to match auditorily presented pseudowords with one of two visually presented shapes, one round and one spiky. The pseudowords were created by crossing either two consonant pairs with a wide range of vowels (experiment 1 and 2) or two vowel pairs with a wide range of consonants (experiment 3). Analyses showed that consonants have a greater influence than vowels in the bouba-kiki effect. Importantly, this asymmetry cannot be due to an onset bias, as a strong consonantal influence is found both with CVCV (experiment 1) and VCV (experiment 2) stimuli. We discuss these results in terms of the differential role of consonants and vowels in speech perception.

Rhythm Is a Marker of Ethnicity in Modern Hebrew: Evidence from a Perception Study and Actors' Ethnicized Portrayals.

In Modern Hebrew, only three segmental markers are typically acknowledged as ethnically conditioned, and usage of these markers has significantly decreased in second and third generation speakers. Yet the sociolinguistic situation of diverging language backgrounds of first generation speakers, compounded with ethnic segregation in housing and the workforce, seems like a fertile ground for social identification from speech. We report two studies on prosodic variation in Modern Hebrew: a perception study and a "matched-pairs" corpus study. The results of the first illustrate that even in the absence of the known segmental markers, ethnicity perception of young native speakers may still diverge between two major ethnic identities, Mizrahi (Middle Eastern) and Ashkenazi (European). The main acoustic correlate was rhythm, measured as the proportional duration of vowels in the utterance. In the second study, actors' speech rhythm was found to be modulated by their portrayed ethnic identity in the same direction, suggesting that this variable is socially salient-and for some speakers, controllable-enough to be involved in style shifting. This study joins a growing body of work illustrating that relatively mild rhythmic variation can contribute to social identification, and in the current case, also for ethnicity portrayal.

(Non)words, (non)words, (non)words: evidence for a protolexicon during the first year of life.

Previous research with artificial language learning paradigms has shown that infants are sensitive to statistical cues to word boundaries (Saffran, Aslin & Newport, 1996) and that they can use these cues to extract word-like units (Saffran, 2001). However, it is unknown whether infants use statistical information to construct a receptive lexicon when acquiring their native language. In order to investigate this issue, we rely on the fact that besides real words a statistical algorithm extracts sound sequences that are highly frequent in infant-directed speech but constitute nonwords. In three experiments, we use a preferential listening paradigm to test French-learning 11-month-old infants' recognition of highly frequent disyllabic sequences from their native language. In Experiments 1 and 2, we use nonword stimuli and find that infants listen longer to high-frequency than to low-frequency sequences. In Experiment 3, we compare high-frequency nonwords to real words in the same frequency range, and find that infants show no preference. Thus, at 11 months, French-learning infants recognize highly frequent sound sequences from their native language and fail to differentiate between words and nonwords among these sequences. These results are evidence that they have used statistical information to extract word candidates from their input and stored them in a 'protolexicon', containing both words and nonwords.

Toddlers' processing of phonological alternations: early compensation for assimilation in English and French.

Using a picture pointing task, this study examines toddlers' processing of phonological alternations that trigger sound changes in connected speech. Three experiments investigate whether 2;5- to 3-year-old children take into account assimilations--processes by which phonological features of one sound spread to adjacent sounds--for the purpose of word recognition (e.g., in English, ten pounds can be produced as te[mp]ounds). English toddlers (n = 18) show sensitivity to native place assimilations during lexical access in Experiment 1. Likewise, French toddlers (n = 27) compensate for French voicing assimilations in Experiment 2. However, French toddlers (n = 27) do not take into account a hypothetical non-native place assimilation rule in Experiment 3, suggesting that compensation for assimilation is already language specific.

English-learning infants' perception of word stress patterns.

Adult speakers of different free stress languages (e.g., English, Spanish) differ both in their sensitivity to lexical stress and in their processing of suprasegmental and vowel quality cues to stress. In a head-turn preference experiment with a familiarization phase, both 8-month-old and 12-month-old English-learning infants discriminated between initial stress and final stress among lists of Spanish-spoken disyllabic nonwords that were segmentally varied (e.g. ['nila, 'tuli] vs [lu'ta, pu'ki]). This is evidence that English-learning infants are sensitive to lexical stress patterns, instantiated primarily by suprasegmental cues, during the second half of the first year of life.

Language-specific stress perception by 9-month-old French and Spanish infants.

During the first year of life, infants begin to have difficulties perceiving non-native vowel and consonant contrasts, thus adapting their perception to the phonetic categories of the target language. In this paper, we examine the perception of a non-segmental feature, i.e. stress. Previous research with adults has shown that speakers of French (a language with fixed stress) have great difficulties in perceiving stress contrasts (Dupoux, Pallier, Sebastián & Mehler, 1997), whereas speakers of Spanish (a language with lexically contrastive stress) perceive these contrasts as accurately as segmental contrasts. We show that language-specific differences in the perception of stress likewise arise during the first year of life. Specifically, 9-month-old Spanish infants successfully distinguish between stress-initial and stress-final pseudo-words, while French infants of this age show no sign of discrimination. In a second experiment using multiple tokens of a single pseudo-word, French infants of the same age successfully discriminate between the two stress patterns, showing that they are able to perceive the acoustic correlates of stress. Their failure to discriminate stress patterns in the first experiment thus reflects an inability to process stress at an abstract, phonological level.

Rapid acquisition of phonological alternations by infants.

We explore whether infants can learn novel phonological alternations on the basis of distributional information. In Experiment 1, two groups of 12-month-old infants were familiarized with artificial languages whose distributional properties exhibited either stop or fricative voicing alternations. At test, infants in the two exposure groups had different preferences for novel sequences involving voiced and voiceless stops and fricatives, suggesting that each group had internalized a different familiarization alternation. In Experiment 2, 8.5-month-olds exhibited the same patterns of preference. In Experiments 3 and 4, we investigated whether infants' preferences were driven solely by preferences for sequences of high transitional probability. Although 8.5-month-olds in Experiment 3 were sensitive to the relative probabilities of sequences in the familiarization stimuli, only 12-month-olds in Experiment 4 showed evidence of having grouped alternating segments into a single functional category. Taken together, these results suggest a developmental trajectory for the acquisition of phonological alternations using distributional cues in the input.

Persistent stress 'deafness': the case of French learners of Spanish.

Previous research by Dupoux et al. [Dupoux, E., Pallier, C., Sebastián, N., & Mehler, J. (1997). A destressing "deafness" in French? Journal of Memory Language 36, 406-421; Dupoux, E., Peperkamp, S., & Sebastián-Gallés (2001). A robust method to study stress' deafness. Journal of the Acoustical Society of America 110, 1608-1618.] found that French speakers, as opposed to Spanish ones, are impaired in discrimination tasks with stimuli that vary only in the position of stress. However, what was called stress 'deafness' was only found in tasks that used high phonetic variability and memory load, not in cognitively less demanding tasks such as single token AX discrimination. This raised the possibility that instead of a perceptual problem, monolingual French speakers might simply lack a metalinguistic representation of contrastive stress, which would impair them in memory tasks. We examined a sample of 39 native speakers of French who underwent formal teaching of Spanish after age 10, and varied in degree of practice in this language. Using a sequence recall task, we observed in all our groups of late learners of Spanish the same impairment in short-term memory encoding of stress contrasts that was previously found in French monolinguals. Furthermore, using a speeded lexical decision task with word-nonword minimal pairs that differ only in the position of stress, we found that all late learners had much difficulty in the use of stress to access the lexicon. Our results show that stress 'deafness' is better interpreted as a lasting processing problem resulting from the impossibility for French speakers to encode contrastive stress in their phonological representations. This affects their memory encoding as well as their lexical access in on-line tasks. The generality of such a persistent suprasegmental 'deafness' is discussed in relation to current findings and models on the perception of non-native phonological contrasts.

Young infants' discrimination of subtle phonetic contrasts.

It is generally accepted that infants initially discriminate native and non-native contrasts and that perceptual reorganization within the first year of life results in decreased discrimination of non-native contrasts, and improved discrimination of native contrasts. However, recent findings from Narayan, Werker, and Beddor (2010) surprisingly suggested that some acoustically subtle native-language contrasts might not be discriminated until the end of the first year of life. We first provide countervailing evidence that young English-learning infants can discriminate the Filipino contrast tested by Narayan et al. when tested in a more sensitive paradigm. Next, we show that young infants learning either English or French can also discriminate comparably subtle non-native contrasts from Tamil. These findings show that Narayan et al.'s null findings were due to methodological choices and indicate that young infants are sensitive to even subtle acoustic contrasts that cue phonetic distinctions cross-linguistically. Based on experimental results and acoustic analyses, we argue that instead of specific acoustic metrics, infant discrimination results themselves are the most informative about the salience of phonetic distinctions.

The role of the striatum in linguistic selection: Evidence from Huntington's disease and computational modeling.

Though accumulating evidence indicates that the striatum is recruited during language processing, the specific function of this subcortical structure in language remains to be elucidated. To answer this question, we used Huntington's disease as a model of striatal lesion. We investigated the morphological deficit of 30 early Huntington's disease patients with a novel linguistic task that can be modeled within an explicit theory of linguistic computation. Behavioral results reflected an impairment in HD patients on the linguistic task. Computational model-based analysis compared the behavioral data to simulated data from two distinct lesion models, a selection deficit model and a grammatical deficit model. This analysis revealed that the impairment derives from an increased randomness in the process of selecting between grammatical alternatives, rather than from a disruption of grammatical knowledge per se. Voxel-based morphometry permitted to correlate this impairment to dorsal striatal degeneration. We thus show that the striatum holds a role in the selection of linguistic alternatives, just as in the selection of motor and cognitive programs.

Relative Difficulty of Understanding Foreign Accents as a Marker of Proficiency.

Foreign-accented speech is generally harder to understand than native-accented speech. This difficulty is reduced for non-native listeners who share their first language with the non-native speaker. It is currently unclear, however, how non-native listeners deal with foreign-accented speech produced by speakers of a different language. We show that the process of (second) language acquisition is associated with an increase in the relative difficulty of processing foreign-accented speech. Therefore, experiencing greater relative difficulty with foreign-accented speech compared with native speech is a marker of language proficiency. These results contribute to our understanding of how phonological categories are acquired during second language learning.

A novel form of perceptual attunement: Context-dependent perception of a native contrast in 14-month-old infants.

By the end of their first year of life, infants have become experts in discriminating the sounds of their native language, while they have lost the ability to discriminate non-native contrasts. This type of phonetic learning is referred to as perceptual attunement. In the present study, we investigated the emergence of a context-dependent form of perceptual attunement in infancy. Indeed, some native contrasts are not discriminated in certain phonological contexts by adults, due to the presence of a language-specific process that neutralizes the contrasts in those contexts. We used a mismatch design and recorded high-density Electroencephalography (EEG) in French-learning 14-month-olds. Our results show that similarly to French adults, infants fail to discriminate a native voicing contrast (e.g., [f] vs. [v]) when it occurs in a specific phonological context (e.g. [ofbe] vs. [ovbe], no mismatch response), while they successfully detected it in other phonological contexts (e.g., [ofne] vs. [ovne], mismatch response). The present results demonstrate for the first time that by the age of 14 months, infants' phonetic learning does not only rely on the processing of individual sounds, but also takes into account in a language-specific manner the phonological contexts in which these sounds occur.

The acquisition of allophonic rules: statistical learning with linguistic constraints.

Phonological rules relate surface phonetic word forms to abstract underlying forms that are stored in the lexicon. Infants must thus acquire these rules in order to infer the abstract representation of words. We implement a statistical learning algorithm for the acquisition of one type of rule, namely allophony, which introduces context-sensitive phonetic variants of phonemes. This algorithm is based on the observation that different realizations of a single phoneme typically do not appear in the same contexts (ideally, they have complementary distributions). In particular, it measures the discrepancies in context probabilities for each pair of phonetic segments. In Experiment 1, we test the algorithm's performances on a pseudo-language and show that it is robust to statistical noise due to sampling and coding errors, and to non-systematic rule application. In Experiment 2, we show that a natural corpus of semiphonetically transcribed child-directed speech in French presents a very large number of near-complementary distributions that do not correspond to existing allophonic rules. These spurious allophonic rules can be eliminated by a linguistically motivated filtering mechanism based on a phonetic representation of segments. We discuss the role of a priori linguistic knowledge in the statistical learning of phonology.