Two-year-olds interpret novel phonological neighbors as familiar words

Minimal gains for minimal pairs: Difficulty in learning similar-sounding words continues into preschool

A critical indicator of spoken language knowledge is the ability to discern the finest possible distinctions that exist between words in a language-minimal pairs, for example, the distinction between the novel words beesh and peesh. Infants differentiate similar-sounding novel labels like "bih" and "dih" by 17 months of age or earlier in the context of word learning. Adult word learners readily distinguish similar-sounding words. What is unclear is the shape of learning between infancy and adulthood: Is there a nonlinear increase early in development, or is there protracted improvement as experience with spoken language amasses? Three experiments tested monolingual English-speaking children aged 3 to 6 years and young adults. Children underperformed when learning minimal-pair words compared with adults (Experiment 1), compared with learning dissimilar words even when speech materials were optimized for young children (Experiment 2), and when the number of word instances during learning was quadrupled (Experiment 3). Nonetheless, the youngest group readily recognized familiar minimal pairs (Experiment 3). Results are consistent with a lengthy trajectory for detailed sound pattern learning in one's native language(s), although other interpretations are possible. Suggestions for research on developmental trajectories across various age ranges are made.

Consequences of phonological variation for algorithmic word segmentation

Over the first year, infants begin to learn the words of their language. Previous work suggests that certain statistical regularities in speech could help infants segment the speech stream into words, thereby forming a proto-lexicon that could support learning of the eventual vocabulary. However, computational models of word segmentation have typically been tested using language input that is much less variable than actual speech is. We show that using actual, transcribed pronunciations rather than dictionary pronunciations of the same speech leads to worse segmentation performance across models. We also find that phonologically variable input poses serious problems for lexicon building, because even correctly segmented word forms exhibit a complex, many-to-many relationship with speakers' intended words. Many phonologically distinct word forms were actually the same intended word, and many identical transcriptions came from different intended words. The fact that previous models appear to have substantially overestimated the utility of simple statistical heuristics suggests a need to consider the formation of the lexicon in infancy differently.

Developmental consistency in the use of subphonemic information during real-time sentence processing

Apparently homophonous sequences contain acoustic information that differentiates their meanings (Gahl, 2008; Quené, 1992). Adults use this information to segment embedded homophones (e.g., ham vs. hamster; Salverda, et al., 2003) in fluent speech. Whether children also do this is unknown, as is whether listeners of any age use such information to disambiguate lexical homophones. In two experiments, 48 English-speaking adults and 48 English-speaking 7- to- 10-year-old children viewed sets of four images and heard sentences containing phonemically identical sequences while their eye movements were continuously tracked. As in previous research, adults showed greater fixation of target meanings when the acoustic properties of an embedded homophone were consistent with the target than when they were consistent with the alternate interpretation. They did not show this difference for lexical homophones. Children's behavior was similar to that of adults, indicating that the use of subphonemic information in homophone processing is consistent over development.

Preschoolers Have Difficulty Discriminating Novel Minimal-Pair Words

PURPOSE

The primary aim was to assess whether children have difficulty distinguishing similar-sounding novel words. The secondary aim was to assess what task characteristics might hinder or facilitate perceptual discrimination.

METHOD

Three within-subjects experiments tested ninety-nine 3- to 5-year-old children total. Experiment 1 presented two cartoon characters each saying a novel word. Children were asked to report whether they said the same word or different words. Words were identical (e.g., deev/deev), were dissimilar (deev/vush), differed in onset consonant voicing (deev/teev), or differed in vowel tenseness (deev/div). Experiment 2 added accuracy feedback after each trial to remind children of task instructions. Experiment 3 interspersed many "same" trials containing a repeating standard word to assess the role of bottom-up stimulus support on difference detection.

RESULTS

The d' scores were highest for dissimilar words, next highest on different-vowel pairs, and lowest on different-consonant pairs. Performance was better with repeated standard stimuli (Experiment 3) than without (Experiment 1). Benefits for repeated task instructions (Experiment 2) were marginal. Exploratory analyses comparing these results to findings in a word-learning study using the same stimuli suggest an imperfect match to how easily children can learn similar-sounding words.

CONCLUSIONS

Overall, similar-sounding novel words are challenging for children to discriminate perceptually, although discrimination scores exceeded chance for all levels of similarity. Clinically speaking, same/different tests may be less sensitive to sound discrimination than change/no-change tests.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.20151848.

A Protracted Developmental Trajectory for English-Learning Children's Detection of Consonant Mispronunciations in Newly Learned Words

Children are adept at learning their language's speech-sound categories, but just how these categories function in their developing lexicon has not been mapped out in detail. Here, we addressed whether, in a language-guided looking procedure, two-year-olds would respond to a mispronunciation of the voicing of the initial consonant of a newly learned word. First, to provide a baseline of mature native-speaker performance, adults were taught a new word under training conditions of low prosodic variability. In a second experiment, 24- and 30-month-olds were taught a new word under training conditions of high or low prosodic variability. Children and adults showed evidence of learning the taught word. Adults' target looking was reduced when the novel word was realized at test with a change in the voicing of the initial consonant, but children did not show any such decrement in target fixation. For both children and adults, most learners did not treat the phonologically distinct variant as a different word. Acoustic-phonetic variability during teaching did not have consistent effects. Thus, under conditions of intensive short-term training, 24- and 30-month-olds did not differentiate a newly learned word from a variant differing only in consonant voicing. High task complexity during training could explain why mispronunciation detection was weaker here than in some prior studies.

Children's disambiguation of novel words varies by the number and position of phonological contrasts

Young children often make pragmatic assumptions when learning new words. For example, they assume that a speaker who uses different words intends to refer to different things - the so-called principle of contrast. We used a standard disambiguation task to explore whether children's assumptions about contrast depend on how much words differ. Three- to 6-year-olds heard pairs of words that differed in terms of the number, position, and types of phonological contrasts. Results indicate that children were less likely to disambiguate words differing by one phoneme than words differing by two or more phonemes, particularly when those one-phoneme differences were located at the beginning or end of the words (as in fim/vim). Overall, the findings suggest that children's pragmatic assumptions about two contrasting words depend not only on if words differ, but also on how they differ.

Perceptual flexibility in word learning: Preschoolers learn words with speech sound variability

Children's language input is rife with acoustic variability. Much of this variability may facilitate learning by highlighting unvarying, criterial speech attributes. But in many cases, learners experience variation in those criterial attributes themselves, as when hearing speakers with different accents. How flexible are children in the face of this variability? The current study taught 3-5-year-olds new words containing speech-sound variability: a single picture might be labeled both deev and teev. After learning, children's knowledge was tested by presenting two pictures and asking them to point to one. Picture-pointing accuracy and eye movements were tracked. While children pointed less accurately and looked less rapidly to dual-label than single-label words, they robustly exceeded chance. Performance was weaker when children learned two distinct labels, such as vayfe and fosh, for a single object. Findings suggest moderate learning even with speech-sound variability. One implication is that neural representations of speech contain rich gradient information.

Repetition, but not acoustic differentiation, facilitates pseudohomophone learning by children

Children's ability to learn words with multiple meanings may be hindered by their adherence to a one-to-one form-to-meaning mapping bias. Previous research on children's learning of a novel meaning for a familiar word (sometimes called a pseudohomophone) has yielded mixed results, suggesting a range of factors that may impact when children entertain a new meaning for a familiar word. One such factor is repetition of the new meaning (Storkel & Maekawa, 2005) and another is the acoustic differentiation of the two meanings (Conwell, 2017). This study asked 72 4-year-old English-learning children to assign novel meanings to familiar words and manipulated how many times they heard the words with their new referents as well as whether the productions were acoustically longer than typical productions of the words. Repetition supported the learning of a pseudohomophone, but acoustic differentiation did not.

Adaptation to an Unfamiliar Accent by Child L2 Listeners

The study examines school-aged L2 listeners' adaptation to an unfamiliar L2 accent and learner variables predicting such adaptation. Fourth-grade Mandarin L1 learners of English as a foreign language (N = 117) listened to a story twice in one of three accent conditions. In the single-talker condition, the story was produced by an Indian English (IE) speaker. In the multi-talker condition, the story was produced by two IE speakers. In the control condition, the story was produced by a Mandarin-accented speaker. Children's (re)interpretation of IE words/nonwords was assessed by referent selection tests administered before and after the first and the second exposures to the story. Repeated exposure to IE-accented speech forms influenced performance: the participants demonstrated better recognition of IE words across the referent selection tests but worse (re)interpretation of IE nonwords sounding similar to existing lexical items. Exposure to an IE-accented story yielded an additional advantage in word recognition, but the advantage was limited to words heard in the story. Furthermore, children's English phonological awareness, phonological memory, and vocabulary predicted their reinterpretation performance of the accented forms. These results suggest that school-aged L2 listeners with better phono-lexical representations develop better capacity in adapting to an unfamiliar accent of a foreign language by loosening their acceptability criteria for word recognition but the adaptation does not necessarily entail perceptual tuning to the specific phonological categories of the accent.

Impacts of acoustic-phonetic variability on perceptual development for spoken language: A review

This article reviews research on when acoustic-phonetic variability facilitates, inhibits, or does not impact perceptual development for spoken language, to illuminate mechanisms by which variability aids learning of language sound patterns. We first summarize structures and sources of variability. We next present proposed mechanisms to account for how and why variability impacts learning. Finally, we review effects of variability in the domains of speech-sound category and pattern learning; word-form recognition and word learning; and accent processing. Variability can be helpful, harmful, or neutral depending on the learner's age and learning objective. Irrelevant variability can facilitate children's learning, particularly for early learning of words and phonotactic rules. For speech-sound change detection and word-form recognition, children seem either unaffected or impaired by irrelevant variability. At the same time, inclusion of variability in training can aid generalization. Variability between accents may slow learning-but with the longer-term benefits of improved comprehension of multiple accents. By highlighting accent as a form of acoustic-phonetic variability and considering impacts of dialect prestige on children's learning, we hope to contribute to a better understanding of how exposure to multiple accents impacts language development and may have implications for literacy development. This article is categorized under: Linguistics > Language Acquisition Psychology > Language Psychology > Perception and Psychophysics.

The development of infants' responses to mispronunciations: A meta-analysis

As they develop into mature speakers of their native language, infants must not only learn words but also the sounds that make up those words. To do so, they must strike a balance between accepting speaker-dependent variation (e.g., mood, voice, accent) but appropriately rejecting variation when it (potentially) changes a word's meaning (e.g., cat vs. hat). This meta-analysis focuses on studies investigating infants' ability to detect mispronunciations in familiar words, or mispronunciation sensitivity. Our goal was to evaluate the development of infants' phonological representations for familiar words as well as explore the role of experimental manipulations related to theoretical questions and of analysis choices. The results show that although infants are sensitive to mispronunciations, they still accept these altered forms as labels for target objects. Interestingly, this ability is not modulated by age or vocabulary size, suggesting that a mature understanding of native language phonology may be present in infants from an early age, possibly before the vocabulary explosion. These results support several theoretical assumptions made in the literature, such as sensitivity to mispronunciation size and position of the mispronunciation. We also shed light on the impact of data analysis choices that may lead to different conclusions regarding the development of infants' mispronunciation sensitivity. Our article concludes with recommendations for improved practice in testing infants' word and sentence processing online. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

How optimal is word recognition under multimodal uncertainty?

Identifying a spoken word in a referential context requires both the ability to integrate multimodal input and the ability to reason under uncertainty. How do these tasks interact with one another? We study how adults identify novel words under joint uncertainty in the auditory and visual modalities, and we propose an ideal observer model of how cues in these modalities are combined optimally. Model predictions are tested in four experiments where recognition is made under various sources of uncertainty. We found that participants use both auditory and visual cues to recognize novel words. When the signal is not distorted with environmental noise, participants weight the auditory and visual cues optimally, that is, according to the relative reliability of each modality. In contrast, when one modality has noise added to it, human perceivers systematically prefer the unperturbed modality to a greater extent than the optimal model does. This work extends the literature on perceptual cue combination to the case of word recognition in a referential context. In addition, this context offers a link to the study of multimodal information in word meaning learning.

Children's Response Bias and Identification of Misarticulated Words

Purpose The purpose of this study was to examine whether children's identification of misarticulated words as real objects was influenced by an inherent bias toward selecting real objects or whether a change in experimental conditions could impact children's selections. Method Forty preschool children aged 4 years 0 months to 6 years 11 months across 2 experiments heard accurate productions of real words (e.g., "leaf"), misarticulated words (e.g., "weaf" and "yeaf"), and unrelated nonwords (e.g., "geem"). Within the misarticulated words, the commonness of the substitute was controlled to be "common" or "uncommon." Using the MouseTracker software, children were asked to select between a real object (e.g., a leaf) and a novel object (Experiment 1) or between a real object (e.g., a leaf) and a blank square, which represented a hidden object (Experiment 2). Results Consistent with previous findings, children chose real objects significantly more when they heard accurate productions (e.g., "leaf") than misarticulated productions (e.g., "weaf" or "yeaf") across both experiments. In misarticulation conditions, real object selections were lower than in the previous study; however, children chose real objects significantly more in the common misarticulation condition than in the uncommon misarticulation condition. Conclusions The results of this study are consistent with previous findings. Children's behavioral responses depended upon the task. Despite these differences in the task, children demonstrated ease in integrating variability into their word identification.

The impact of cross-language phonological overlap on bilingual and monolingual toddlers' word recognition

We examined how L2 exposure early in life modulates toddler word recognition by comparing German-English bilingual and German monolingual toddlers' recognition of words that overlapped to differing degrees, measured by number of phonological features changed, between English and German (e.g., identical, 1-feature change, 2-feature change, 3-feature change, no overlap). Recognition in English was modulated by language background (bilinguals vs. monolinguals) and by the amount of phonological overlap that English words shared with their L1 German translations. L1 word recognition remained unchanged across conditions between monolingual and bilingual toddlers, showing no effect of learning an L2 on L1 word recognition in bilingual toddlers. Furthermore, bilingual toddlers who had a later age of L2 acquisition had better recognition of words in English than those toddlers who acquired English at an earlier age. The results suggest an important role for L1 phonological experience on L2 word recognition in early bilingual word recognition.

Vocal production and novel word learning in the first year

Previous studies have demonstrated an effect of early vocal production on infants' speech processing and later vocabulary. This study focuses on the relationship between vocal production and new word learning. Thirty monolingual Italian-learning infants were recorded at about 11 months, to establish the extent of their consonant production. In parallel, the infants were trained on novel word-object pairs, two consisting of early learned consonants (ELC), two consisting of late learned consonants (LLC). Word learning was assessed through Preferential Looking. The results suggest that vocal production supports word learning: Only children with higher, consistent consonant production attended more to the trained ELC images.

A cross-linguistic examination of toddlers' interpretation of vowel duration

Languages differ in their phonological use of vowel duration. For the child, learning how duration contributes to lexical contrast is complicated because segmental duration is implicated in many different linguistic distinctions. Using a language-guided looking task, we measured English and Dutch 21-month-olds' recognition of familiar words with normal or manipulated vowel durations. Dutch but not English learners were affected by duration changes, even though distributions of short and long vowels in both languages are similar, and English uses vowel duration as a cue to (for example) consonant coda voicing. Additionally, we found that word recognition in Dutch toddlers was affected by shortening but not lengthening of vowels, matching an asymmetry also found in Dutch adults. Considering the subtlety of the crosslinguistic difference in the input, and the complexity of duration as a phonetic feature, our results suggest a strong capacity for phonetic analysis in children before their second birthday.

Children's gradient sensitivity to phonological mismatch: considering the dynamics of looking behavior and pupil dilation

In a preferential looking paradigm, we studied how children's looking behavior and pupillary response were modulated by the degree of phonological mismatch between the correct label of a target referent and its manipulated form. We manipulated degree of mismatch by introducing one or more featural changes to the target label. Both looking behavior and pupillary response were sensitive to degree of mismatch, corroborating previous studies that found differential responses in one or the other measure. Using time-course analyses, we present for the first time results demonstrating full separability among conditions (detecting difference not only between one vs. more, but also between two and three featural changes). Furthermore, the correct labels and small featural changes were associated with stable target preference, while large featural changes were associated with oscillating looking behavior, suggesting significant shifts in looking preference over time. These findings further support and extend the notion that early words are represented in great detail, containing subphonemic information.

Word Level Stress and Lexical Processing in 17-Month-Old Infants

Detailed representations enable infants to distinguish words from one another and more easily recognize new words. We examined whether 17-month-old infants encode word stress in their familiar word representations. In Experiment 1, infants were presented with pairs of familiar objects while hearing a target label either properly pronounced with the correct stress (e.g., baby /'beɪbi/) or mis-pronounced with the incorrect stress pattern (e.g., baby /beɪ'bi/). Infants mapped both the correctly stressed and mis-stressed labels to the target objects; however, they were slower to fixate the target when hearing the mis-stressed label. In Experiment 2, we examined whether infants appreciate that stress has a nonproductive role in English (i.e., altering the stress of a word does not typically signal a change in word meaning) by presenting infants with a familiar object paired with a novel object while hearing either correctly stressed or mis-stressed familiar words (Experiment 2). Here, infants mapped the correctly stressed label to the familiar object but did not map the mis-stressed label reliably to either the target or distractor objects. These findings suggest that word stress impacts the processing of familiar words, and infants have burgeoning knowledge that altering the stress pattern of a familiar word does not reliably signal a new referent.

The infant's developmental path in phonological acquisition

Research on how language acquisition begins has been fragmented both in terms of scientific communities and in terms of the phenomena that are taken to characterize developmental progress. In her article, Marilyn Vihman argues for an integrative approach that takes the child's efforts at speech production as primary, and notes that infants' knowledge of how words sound may accrue over a protracted period developmentally. Here, I briefly discuss how reconceptualization of the process can help integrate perspectives previously at odds.