The threshold of rule productivity in infants.

Most learning theories agree that the productivity of a rule or a pattern relies on regular exemplars being dominant over exceptions; the threshold for productivity is, however, unclear; moreover, gradient productivity levels are assumed for different rules/patterns, regular or irregular. One theory by Yang, the Tolerance Principle (TP), specified a productivity threshold applicable to all rules, calculated by the numbers of total exemplars and exceptions of a rule; furthermore, rules are viewed as quantal, either productive or unproductive, with no gradient levels. We evaluated the threshold and gradience-quantalness questions by investigating infants' generalization. In an implicit learning task, 14-month-olds heard exemplars of an artificial word-order rule and exceptions; their distributions were set closed to the TP-threshold (5.77) on both sides: 11 regular exemplars vs. 5 exceptions in Condition 1 (productiveness predicted), and 10 regular exemplars vs. 6 exceptions in Condition 2 (unproductiveness predicted). These predictions were pitted against those of the statistical majority threshold (50%), a common assumption which would predict generalization in both conditions (68.75, 62.5%). Infants were tested on the trained rule with new exemplars. Results revealed generalization in Condition 1, but not in Condition 2, supporting the TP-threshold, not the statistical majority threshold. Gradience-quantalness was assessed by combined analyses of Conditions 1-2 and previous experiments by Koulaguina and Shi. The training across the conditions contained gradually decreasing regular exemplars (100, 80, 68.75, 62.5, 50%) relative to exceptions. Results of test trials showed evidence for quantalness in infants (productive: 100, 80, 68.75%; unproductive: 62.5, 50%), with no gradient levels of productivity.

When language-general and language-specific processes are in conflict: The case of sub-syllabic word segmentation in toddlers.

Infants use statistics-based word segmentation strategies from the preverbal stage. Statistical segmentation is, however, constrained by the Onset Bias, a language-universal principle that disfavors segmentation that harms syllable integrity. Children eventually learn language-specific exceptions to this principle. For instance, sub-syllabic parsing occurs for vowel-initial words in French liaison contexts, that is, when a word's final consonant surfaces as the following word's syllabic onset (e.g., /n/ in un /n/éléphant). In past research, French-learning 24-month-olds succeeded in parsing a vowel-initial pseudo-word surfacing with variable liaison consonants. This study further investigated infants' liaison representation, its potential impacts on parsing, and its interaction with the Onset Bias. In Experiments 1 and 2, French-learning 24-month-olds were familiarized with pseudo-words with variable liaison-like versus nonliaison-like onset consonants, preceded by words that cannot trigger those onsets (e.g., un zonche; un gonche). We found no mis-segmentation as vowel-initial and successful segmentation as consonant-initial. In Experiment 3, when the preceding words could trigger a liaison consonant that matched the onset of the following word (e.g., un nonche), infants showed a vowel-initial mis-interpretation, against the Onset Bias, revealing an effect of liaison knowledge. These results demonstrate that toddlers balance their use of language-general principles/strategies and language-specific knowledge during early acquisition.

Mandarin-learning 19-month-old toddlers' sensitivity to word order cues that differentiate unaccusative and unergative verbs.

Languages employ different means to manifest the unaccusative-unergative distinction. In Mandarin Chinese, unaccusative verbs are allowed in the inversion construction "V-le NP", while unergative verbs are not. This grammaticality contrast brings a presence/absence contrast between the two verb classes in the inversion construction in the input. Using an eye fixation task, we investigated whether Mandarin-learning 19-month-olds were sensitive to this specific input frequency contrast. We found that infants distinguished the grammatical versus ungrammatical uses of the two verb classes in the inversion construction "V-le NP" (Experiment 1). When the verb classes were in the "NP V-le" order (Experiment 2) (i.e., the same level of grammaticality), infants showed no evidence of a looking difference. These responses indicate toddlers' sensitivity to the distribution of the two verb classes in the inversion construction. This distributional information is likely to be one of the potential cues that facilitate their acquisition of the unaccusative-unergative distinction.

Variable forms in French-learning toddlers' lexical representations.

We investigated toddlers' phonological representations of common vowel-initial words that can take on multiple surface forms in the input. In French, liaison consonants are inserted and are syllabified as onsets in subsequent vowel-initial words, for example, petit /t/ éléphant [little elephant]. We aimed to better understand the impact on children's early lexical representations of this frequent intrusion by consonants by testing whether toddlers store multiple forms for vowel-initial words (e.g., téléphant, zéléphant) early in acquisition. Thirty-one Quebec French-learning 30-month-olds completed an eye-tracking experiment (16 girls). Children were predominantly from White, middle-class families living in a large urban area (Montreal). Each trial presented two objects while one of them was named. There were four key trial types: (a) correct vowel-initial (e.g., joli éléphant [pretty elephant]); (b) pragmatically incorrect frequent intrusion (e.g., joli zéléphant, /z/ intrusion [pretty elephants], which is grammatically acceptable but does not correspond to the picture); (c) lexically incorrect frequent intrusion (e.g., joli téléphant, /t/ intrusion, as /t/ is a frequent liaison consonant in general but is impossible with joli); (d) lexically incorrect infrequent intrusion (e.g., joli géléphant, /g/ intrusion, as /g/ is an infrequent liaison consonant and is also impossible with joli). The results showed that target recognition was successful in the frequent /t/- and /z/-intrusion trials and was also evident in the vowel-initial trials, whereas it was impeded in the infrequent /g/-intrusion trials. Our findings demonstrate that French-learning children's early lexicon contains multiple variants for words that are subject to phonological alternations, including frequent liaison-consonant variants. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

14-month-olds exploit verbs' syntactic contexts to build expectations about novel words.

During their second year of life, infants develop a rudimentary understanding of grammatical categories based on their knowledge and use of frequent function words. The current study inquired whether, at only 14 months of age, infants can track co-occurrence patterns between function words and content words (e.g., determiners can precede nouns, and pronouns can precede verbs), and use these previously encountered syntactic contexts to build expectations about which function words can co-occur with novel words. Using a habituation paradigm, French-learning 14-month-olds were presented with utterances containing two novel words preceded by function words (either two determiners in the Novel Nouns condition or two pronouns in the Novel Verbs conditions). We found that at test, infants looked longer during trials in which the novel words occurred in an unexpected syntactic context (following a pronoun for infants in the Novel Nouns condition and following a determiner for infants in the pooled analysis of the three Novel Verbs conditions). Hence, our results confirm previous findings on infants' sensitivity to noun contexts and most importantly demonstrate that their sensitivity to the co-occurrence of verbs with pronouns begins much earlier than previously understood.

Is prosodic information alone sufficient for guiding early grammatical acquisition?

An infant perceptual experiment investigated the role of prosody. All-nonsense-word sentences (e.g., Guin felli crale vur ti gosine), each in structure 1 ([[Determiner + Adjective + Noun] [Verb + Determiner + Noun]]) and structure 2 ([[Determiner + Noun] [Verb + Preposition + Determiner + Noun]]), were recorded (by mimicking real-word French sentences) with disambiguating prosodic groupings matching the two major constituents. French-learning 20- and 24-month-olds were familiarized with either structure 1 or structure 2. All infants were tested with noun-use trials (e.g., Le crale "the crale-Noun") versus verb-use trials (Tu crales "You crale-Verb"). Structure-2-familiarized infants, but not structure-1-familiarized infants, discriminated the test trials, demonstrating that prosody alone guides verb categorization. Noun categorization requires determiners, as shown in earlier work [S. Massicotte-Laforge and R. Shi, J. Acoust. Soc. Am. 138(4), EL441-EL446 (2015)].

Grammatical Aspect in Early Child Mandarin: Evidence from a Preferential Looking Experiment.

The study assessed 30-month-old Mandarin-speaking children's awareness of aspectual distinctions involving the perfective marker le and the imperfective marker zhe in a preferential looking experiment. In the experiment, we presented our child subjects with a choice between two video clips (one depicting a closed event and the other depicting an on-going event), in the presence of an auditory stimulus (either the le sentence, the zhe sentence or the control sentence without any aspect marker). Children's looking behavior in the task was recorded and analyzed. The results revealed 30-month-old children's emerging sensitivity to the aspectual contrast between le and zhe. This was manifest by an increase in looking to the closed event when hearing the le sentence and an increase in looking to the on-going event when hearing the zhe sentence. The absence of le or zhe in the control sentence did not result in any increase or decrease in looking to either event. We also found that the effect of le on children's looking behavior was immediate whereas the effect of zhe was late. We attributed this difference to the facilitative role of le in children's sentence processing as well as their preference for the event boundary. The results lend support to the continuity view that functional morphemes like aspect markers are available to children early in language development.

Perception and Representation of Lexical Tones in Native Mandarin-Learning Infants and Toddlers.

We investigated the perceptual development of lexical tones in native tone-learning infants during the first 2 years of life, focusing on two important stages of phonological acquisition: the preverbal and vocabulary explosion stages. Experiment 1 examined monolingual Mandarin-Chinese-learning 4- to 13-month-olds' discrimination of similar lexical tones in Mandarin, Tone 2 (T2, rising) vs. Tone 3 (T3, low-dipping). Infants were habituated to exemplars of one tone (either T2 or T3), and tested with new exemplars of the habituated tone vs. the contrasting tone. Results show that looking time increased for the contrasting tone, but not for new exemplars of the habituated tone, suggesting that infants discriminated the two tones as separate categories. Furthermore, infants' discrimination of the tones was comparable across ages. Experiment 2 tested whether tones are distinguished in toddlers' lexicon. Monolingual Mandarin-learning 19- to 26-month-olds were presented with pairs of objects while one was named. Targets were familiar words bearing T2 or T3, either correctly pronounced (CP) or mispronounced (MP) in tone. We found that word recognition was equally successful in CP and in MP trials when T2 was mispronounced as T3 and T3 as T2, indicating that T2 and T3 are confusable. In contrast, recognition failed when T2 and T3 words were mispronounced as Tone 4 (T4, falling), showing that T4 was represented as a distinct category. Results show that toddlers have difficulty encoding similar tones distinctly in known words. The T2-T3 contrast is particularly challenging because of Tone 3 Sandhi, which changes T3 to T2 when it precedes another T3. At the stage when toddlers track the meaning of T2 and T3 words and track the sandhi alternations, they seem to overgeneralize the two tones as variants of one functional category, reflecting perceptual organization at the level of phonemic learning.

The role of prosody in infants' early syntactic analysis and grammatical categorization.

This study tested the hypothesis that phrasal prosody assists early syntactic acquisition. Stimulus-sentences consisting of French determiners and pseudo-lexical-words were ambiguous between two syntactic structures, e.g., [[TonDet felliAdj craleN]NP [vurV laDet gosineN]VP] versus [[TonDet felliN]NP [craleV vurPrep laDet gosineN]VP], which had distinct prosodic cues. French-learning 20-month-olds were familiarized with the sentences either in the prosody of one structure, or the other structure. All infants were tested with Det + N (e.g., LeDet craleN) versus Pron + V (e.g., TuPron cralesV) trials containing non-familiarized functors. Infants perceived the test-stimuli according to the familiarized structure. They used prosody to categorize words and interpret adjacent and non-adjacent syntactic dependencies.

Representations of abstract grammatical feature agreement in young children.

A fundamental question in language acquisition research is whether young children have abstract grammatical representations. We tested this question experimentally. French-learning 30-month-olds were first taught novel word-object pairs in the context of a gender-marked determiner (e.g., un MASC ravole 'a ravole'). Test trials presented the objects side-by-side while one of them was named in new phrases containing other determiners and an adjective (e.g., le MASC joli ravole MASC 'the pretty ravole'). The gender agreement between the new determiner and the non-adjacent noun was manipulated in different test trials (e.g., le MASC __ravole MASC; *la FEM __ravole MASC). We found that online comprehension of the named target was facilitated in gender-matched trials but impeded in gender-mismatched trials. That is, children assigned the determiner genders to the novel nouns during word learning. They then processed the non-adjacent gender agreement between the two categories (Det, Noun) during test. The results demonstrate abstract featural representation and grammatical productivity in young children.

Distributional cues and the onset bias in early word segmentation.

In previous infant studies on statistics-based word segmentation, the unit of statistical computation was always aligned with the syllabic edge, which had a consonant onset. The current study addressed whether the learning system imposes a constraint that favors word forms beginning with a consonant onset over those beginning with an onsetless sub-syllable, by examining infants' segmentation of vowel-initial non-words in French liaison. French-learning 20- and 24-month-old infants (N = 64) were familiarized with sentences containing variable liaison consonants preceding the same vowel-initial non-word (e.g., /n/onche, /z/onche, /r/onche, /t/onche), such that the distributional cues supported the sub-syllabic target (e.g., onche). After familiarization, we tested sub-syllabic statistical segmentation by presenting the vowel-initial target (e.g., onche) versus another non-familiarized vowel-initial word (e.g., èque). Another group of infants was tested with a consonant-initial mis-segmentation of the target (e.g., zonche) versus another non-familiarized consonant-initial word (e.g., zèque). Results showed that 20-month-olds failed to segment the vowel-initial targets, but they mis-segmented the targets as consonant-initial, indicating that the onset bias dominated over sub-syllabic statistics for word segmentation at this age. Twenty-four-month-olds showed ambiguous interpretations (i.e., both vowel-initial segmentation and consonant-initial mis-segmentation), suggesting that the use of statistics to segment sub-syllabic words was emerging while the onset bias continued to have an impact.

Abstract rule learning in 11- and 14-month-old infants.

This study tests the hypothesis that distributional information can guide infants in the generalization of word order movement rules at the initial stage of language acquisition. Participants were 11- and 14-month-old infants. Stimuli were sentences in Russian, a language that was unknown to our infants. During training the word order of each sentence was transformed following a consistent pattern (e.g., ABC-BAC). During the test phase infants heard novel sentences that respected the trained rule and ones that violated the trained rule (i.e., a different transformation such as ABC-ACB). Stimuli words had highly variable phonological and morphological shapes. The cue available was the positional information of words and their non-adjacent relations across sentences. We found that 14-month-olds, but not 11-month-olds, showed evidence of abstract rule generalization to novel instances. The implications of this finding to early syntactic acquisition are discussed.

Development of abstract grammatical categorization in infants.

This study examined abstract syntactic categorization in infants, using the case of grammatical gender. Ninety-six French-learning 14-, 17-, 20-, and 30-month-olds completed the study. In a preferential looking procedure infants were tested on their generalized knowledge of grammatical gender involving pseudonouns and gender-marking determiners. The pseudonouns were controlled to contain no phonological or acoustical cues to gender. The determiner gender feature was the only information available. During familiarization, some pseudonouns followed a masculine determiner and others a feminine determiner. Test trials presented the same pseudonouns with different determiners in correct (consistent with familiarization gender pairing) versus incorrect gender agreement. Twenty-month-olds showed emerging knowledge of gender categorization and agreement. This knowledge was robust in 30-month-olds. These findings demonstrate that abstract, productive grammatical representations are present early in acquisition.

Toddlers use the number feature in determiners during online noun comprehension.

Function words support many aspects of language acquisition. This study investigated whether toddlers understand the number feature of determiners and use it for noun comprehension. French offers an ideal "test case" as number is phonetically marked in determiners but not in nouns. Twenty French-learning 24-month-olds completed a split-screen experiment. Looking times to target pictures were measured under 3 trial types varying in the degree to which the determiner matched the number displayed in the object(s). Children looked longer when the determiner matched the object(s), and were confused in trials of clear mismatch. Importantly, their processing resembled that of French adults (D. Dahan, D. Swingley, M. K. Tanenhaus, & J. S. Magnuson, 2000). Thus, children understand the determiner number feature early in acquisition and use this knowledge to constrain online comprehension.

Initial morphological learning in preverbal infants.

How do children learn the internal structure of inflected words? We hypothesized that bound functional morphemes begin to be encoded at the preverbal stage, driven by their frequent occurrence with highly variable roots, and that infants in turn use these morphemes to interpret other words with the same inflections. Using a preferential looking procedure, we showed that French-learning 11-month-olds encoded the frequent French functor /e/, and perceived bare roots and their inflected variants as related forms. In another experiment an added training phase presented an artificial suffix co-occurring with many pseudo-roots. Infants learned the new suffix and used it to interpret novel affixed words that never occurred during the training. These findings demonstrate that initial learning of sub-lexical functors and morphological alternations is frequency-based, without relying on word meaning.

A connectionist study on the role of pitch in infant-directed speech.

Infant-directed speech (IDS) is believed to facilitate language learning. However, the benefit may be either due to clearer acoustic correlates to linguistic structures, or simply increased attention from infants induced by IDS exaggerated prosody. This study investigated the pure effect of IDS pitch on lexical tone learning, with attentional/affective factors removed by using artificial neural networks. Following training with the pitch of Mandarin tones in IDS versus adult-directed speech, the networks yielded equal tonal categorization for both registers. IDS pitch produced no additional linguistic support. IDS pitch appears to strictly play the non-linguistic role of attention/affect, which may indirectly benefit learning.

Infants' sensitivity to non-adjacent dependencies across phonological phrase boundaries.

Natural languages contain numerous non-adjacent relationships between words or morphemes in a sentence, often straddling phonological phrase boundaries (e.g., [these sheep] [have [ellipsis (horizontal)]]). Since phonological phrases are considered the main processing unit for infants, this may cause the acquisition of cross-phrase dependencies to be challenging. This study, however, shows that by 17 months of age, French-learning infants have nonetheless gained sensitivity to remote determiner-auxiliary co-occurrences that are interceded by phonological phrase boundaries. Infants thus possess a robust mechanism for tracking non-adjacent dependencies. This ability is essential for early grammatical development.

Syntactic Categorization in French-Learning Infants.

Recent work showed that infants recognize and store function words starting from the age of 6-8 months. Using a visual fixation procedure, the present study tested whether French-learning 14-month-olds have the knowledge of syntactic categories of determiners and pronouns, respectively, and whether they can use these function words for categorizing novel words to nouns and verbs. The prosodic characteristics of novel words stimuli for noun versus verb uses were balanced. The only distinguishing cue was the preceding determiners versus subject pronouns, the former being the most common for nouns and the latter the most common for verbs, i.e., Det + Noun, Pron + Verb. We expected that noun categorization may be easier than verb categorization because the co-occurrence of determiners with nouns is more consistent than that of subject pronouns with verbs in French. The results showed that infants grouped the individual determiners as one common class, and that they appeared to use the determiners to categorize novel words into nouns. However, we found no evidence of verb categorization. Unlike determiners, pronouns were not perceived as a common syntactic class.

French-learning toddlers use gender information on determiners during word recognition.

In gender-marking languages, the gender of the noun determines the form of the preceding article. In this study, we examined whether French-learning toddlers use gender-marking information on determiners to recognize words. In a split-screen preferential looking experiment, 25-month-olds were presented with picture pairs that referred to nouns with either the same or different genders. The target word in the auditory instruction was preceded either by the correct or incorrect gender-marked definite article. Toddlers' looking times to target shortly after article onset demonstrated that target words were processed most efficiently in different-gender grammatical trials. While target processing in same-gender grammatical trials recovered in the subsequent time window, ungrammatical articles continued to affect processing efficiency until much later in the trial. These results indicate that by 25 months of age, French-learning toddlers use gender information on determiners when comprehending subsequent nouns.

The effect of functional morphemes on word segmentation in preverbal infants.

This study examines the role of functional morphemes in the earliest stage of lexical development. Recent research showed that prelinguistic infants can perceive functional morphemes. We inquire whether infants use frequent functors to segment potential word forms. French-learning 8-month-olds were familiarized to two utterance types: a novel noun following a functor, and another novel noun following a prosodically matched nonsense functor. After familiarization, infants' segmentation of the two nouns was assessed in a test phase presenting the nouns in isolation. Infants in Experiment 1 showed evidence of using both frequent functors des and mes (as opposed to the nonsense functor kes) to segment the nouns, suggesting also that they had specific representations of the functors. The infrequent functor vos in Experiment 2 did not facilitate segmentation. Frequency is thus a crucial factor. Our findings demonstrate that frequent functors can bootstrap infants into early lexical learning. Furthermore, the effect of functors for initial word segmentation is likely universal.