Form is easy,meaning is hard: resolving a paradox in early child language

A developmental paradox is discussed: studies of infant processing of language and language-like stimuli indicate considerable ability to abstract patterns over specific items and to distinguish natural from unnatural English sentences. In contrast, studies of toddler language production find little ability to generalize patterns over specific English words or constructions. Thus, infants appear to be abstract auditory or language processors whereas toddlers appear to be non-abstract, item-specific language users. Three resolutions are offered to this paradox. The first, that no resolution is necessary because only the toddler findings come from language use in a communicative context and so only the toddler findings are relevant to linguistic knowledge, is rejected. The second, that the contradictions are rooted in the differing methodologies of the two sets of studies (comprehension vs. production), is found to explain important aspects of the contradictory findings. The third, that the contractions come from the differing content of the stimuli in the studies, is also found to be explanatory and is argued to carry greater weight. Resolution 3 suggests that the patterns that infants extract from their linguistic input are not yet tied to meaning; thus, toddlers do not lose these earlier-abstracted forms but their use of them is limited until they have been integrated with meaning. It is argued that in language acquisition, learning form is easy but learning meaning, and especially linking meanings and forms, is hard.     

The profile of abstract rule learning in infancy: Meta‐analytic and experimental evidence

Everyone agrees that infants possess general mechanisms for learning about the world, but the existence and operation of more specialized mechanisms is controversial. One mechanism—rule learning—has been proposed as potentially specific to speech, based on findings that 7‐month‐olds can learn abstract repetition rules from spoken syllables (e.g. ABB patterns: wo‐fe‐fe, ga‐tu‐tu…) but not from closely matched stimuli, such as tones. Subsequent work has shown that learning of abstract patterns is not simply specific to speech. However, we still lack a parsimonious explanation to tie together the diverse, messy, and occasionally contradictory findings in that literature. We took two routes to creating a new profile of rule learning: meta‐analysis of 20 prior reports on infants’ learning of abstract repetition rules (including 1,318 infants in 63 experiments total), and an experiment on learning of such rules from a natural, non‐speech communicative signal. These complementary approaches revealed that infants were most likely to learn abstract patterns from meaningful stimuli. We argue that the ability to detect and generalize simple patterns supports learning across domains in infancy but chiefly when the signal is meaningfully relevant to infants’ experience with sounds, objects, language, and people.     

Visual statistical learning in infancy: evidence for a domain general learning mechanism

The rapidity with which infants come to understand language and events in their surroundings has prompted speculation concerning innate knowledge structures that guide language acquisition and object knowledge. Recently, however, evidence has emerged that by 8 months, infants can extract statistical patterns in auditory input that are based on transitional probabilities defining the sequencing of the input's components (Science 274 (1996) 1926). This finding suggests powerful learning mechanisms that are functional in infancy, and raises questions about the domain generality of such mechanisms. We habituated 2-, 5-, and 8-month-old infants to sequences of discrete visual stimuli whose ordering followed a statistically predictable pattern. The infants subsequently viewed the familiar pattern alternating with a novel sequence of identical stimulus components, and exhibited significantly greater interest in the novel sequence at all ages. These results provide support for the likelihood of domain general statistical learning in infancy, and imply that mechanisms designed to detect structure inherent in the environment may play an important role in cognitive development.     

Rule learning by cotton-top tamarins

Previous work suggests that human infants are capable of rapidly generalizing patterns that have been characterized as abstract algebraic rules (Science 283 (1999) 77), a process that may play a pivotal role in language acquisition. Here we explore whether this capacity is uniquely human and evolved specifically for the computational problems associated with language, or whether this mechanism is shared with other species, and therefore evolved for problems other than language. We used the same materials and methods that were originally employed in tests of human infants to assess whether cotton-top tamarin monkeys can extract abstract algebraic rules. Specifically, we habituated subjects to sequences of consonant-vowel syllables that followed one of two patterns, AAB (e.g. wi wi di) or ABB (le we we). Following habituation, we presented subjects with two novel test items, one with the same pattern as that presented during habituation and one with a different pattern. Like human infants, tamarins were more likely to dishabituate to the test item with a different pattern. We conclude that the capacity to generalize rule-like patterns, at least at the level demonstrated, did not evolve specifically for language acquisition, though it remains possible that infants might use such rules during language acquisition.     

Language specific prosodic preferences during the first half year of life: Evidence from German and French infants

There is converging evidence that infants are sensitive to prosodic cues from birth onwards and use this kind of information in their earliest steps into the acquisition of words and syntactic regularities of their target language. Regarding word segmentation, it has been found that English-learning infants segment trochaic words by 7.5 months of age, and iambic words only by 10.5 months of age [Jusczyk, P. W., Houston, D. M., & Newsome, M. (1999). The beginnings of word segmentation in English-learning infants. Cognitive Psychology, 39, 159–207]. The question remains how to interpret this finding in relation to results showing that English-learning infants develop a preference for trochaic over iambic words between 6 and 9 months of age [Jusczyk, P. W., Cutler, A., & Redanz, N. (1993). Preference for the predominant stress patterns of English words. Child Development, 64, 675–687]. In the following, we report the results of four experiments using the headturn preference procedure (HPP) to explore the trochaic bias issue in German- and French-learning infants. For German, a trochaic preference was found at 6 but not at 4 months, suggesting an emergence of this preference between both ages (Experiments 1 and 2). For French, 6-month-old infants did not show a preference for either stress pattern (Experiment 3) while they were found to discriminate between the two stress patterns (Experiment 4). Our findings are the first to demonstrate that the trochaic bias is acquired by 6 months of age, is language specific and can be predicted by the rhythmic properties of the language in acquisition. We discuss the implications of this very early acquisition for our understanding of the emergence of segmentation abilities.     

Learning words’ sounds before learning how words sound: 9-Month-olds use distinct objects as cues to categorize speech information

One of the central themes in the study of language acquisition is the gap between the linguistic knowledge that learners demonstrate, and the apparent inadequacy of linguistic input to support induction of this knowledge. One of the first linguistic abilities in the course of development to exemplify this problem is in speech perception: specifically, learning the sound system of one’s native language. Native-language sound systems are defined by meaningful contrasts among words in a language, yet infants learn these sound patterns before any significant numbers of words are acquired. Previous approaches to this learning problem have suggested that infants can learn phonetic categories from statistical analysis of auditory input, without regard to word referents. Experimental evidence presented here suggests instead that young infants can use visual cues present in word-labeling situations to categorize phonetic information. In Experiment 1, 9-month-old English-learning infants failed to discriminate two non-native phonetic categories, establishing baseline performance in a perceptual discrimination task. In Experiment 2, these infants succeeded at discrimination after watching contrasting visual cues (i.e., videos of two novel objects) paired consistently with the two non-native phonetic categories. In Experiment 3, these infants failed at discrimination after watching the same visual cues, but paired inconsistently with the two phonetic categories. At an age before which memory of word labels is demonstrated in the laboratory, 9-month-old infants use contrastive pairings between objects and sounds to influence their phonetic sensitivity. Phonetic learning may have a more functional basis than previous statistical learning mechanisms assume: infants may use cross-modal associations inherent in social contexts to learn native-language phonetic categories.     

Statistical learning of tone sequences by human infants and adults

Previous research suggests that language learners can detect and use the statistical properties of syllable sequences to discover words in continuous speech (e.g. Aslin, R.N., Saffran, J.R., Newport, E.L., 1998. Computation of conditional probability statistics by 8-month-old infants. Psychological Science 9, 321-324; Saffran, J.R., Aslin, R.N., Newport, E.L., 1996. Statistical learning by 8-month-old infants. Science 274, 1926-1928; Saffran, J., R., Newport, E.L., Aslin, R.N., (1996). Word segmentation: the role of distributional cues. Journal of Memory and Language 35, 606-621; Saffran, J.R., Newport, E.L., Aslin, R.N., Tunick, R.A., Barrueco, S., 1997. Incidental language learning: Listening (and learning) out of the corner of your ear. Psychological Science 8, 101-195). In the present research, we asked whether this statistical learning ability is uniquely tied to linguistic materials. Subjects were exposed to continuous non-linguistic auditory sequences whose elements were organized into 'tone words'. As in our previous studies, statistical information was the only word boundary cue available to learners. Both adults and 8-month-old infants succeeded at segmenting the tone stream, with performance indistinguishable from that obtained with syllable streams. These results suggest that a learning mechanism previously shown to be involved in word segmentation can also be used to segment sequences of non-linguistic stimuli.     

Emotional facial expressions affect visual rule learning in 7- to 8-month-old infants

Rule learning (RL) is an implicit learning mechanism that allows infants to detect and generalize rule-like repetition-based patterns (such as ABB and ABA) from a sequence of elements. Increasing evidence shows that RL operates both in the auditory and the visual domain and is modulated by the perceptual expertise with the to-be-learned stimuli. Yet, whether infants’ ability to detect a high-order rule from a sequence of stimuli is affected by affective information remains a largely unexplored issue. Using a visual habituation paradigm, we investigated whether the presence of emotional expressions with a positive and a negative value (i.e., happiness and anger) modulates 7- to 8-month-old infants’ ability to learn a rule-like pattern from a sequence of faces of different identities. Results demonstrate that emotional facial expressions (either positive and negative) modulate infants’ visual RL mechanism, even though positive and negative facial expressions affect infants’ RL in a different manner: while anger disrupts infants’ ability to learn the rule-like pattern from a face sequence, in the presence of a happy face infants show a familiarity preference, thus maintaining their learning ability. These findings show that emotional expressions exert an influence on infants’ RL abilities, contributing to the investigation on how emotion and cognition interact in face processing during infancy.     

Consonants and vowels: different roles in early language acquisition

Language acquisition involves both acquiring a set of words (i.e. the lexicon) and learning the rules that combine them to form sentences (i.e. syntax). Here, we show that consonants are mainly involved in word processing, whereas vowels are favored for extracting and generalizing structural relations. We demonstrate that such a division of labor between consonants and vowels plays a role in language acquisition. In two very similar experimental paradigms, we show that 12-month-old infants rely more on the consonantal tier when identifying words (Experiment 1), but are better at extracting and generalizing repetition-based srtuctures over the vocalic tier (Experiment 2). These results indicate that infants are able to exploit the functional differences between consonants and vowels at an age when they start acquiring the lexicon, and suggest that basic speech categories are assigned to different learning mechanisms that sustain early language acquisition.     

Infant artificial language learning and language acquisition

The rapidity with which children acquire language is one of the mysteries of human cognition. A view held widely for the past 30 years is that children master language by means of a language-specific learning device. An earlier proposal, which has generated renewed interest, is that children make use of domain-general, associative learning mechanisms. However, our current lack of knowledge of the actual learning mechanisms involved during infancy makes it difficult to determine the relative contributions of innate and acquired knowledge. A recent approach to studying this problem exposes infants to artificial languages and assesses the resulting learning. In this article, we review studies using this paradigm that have led to a number of exciting discoveries regarding the learning mechanisms available during infancy. These studies raise important issues with respect to whether such mechanisms are general or specific to language, the extent to which they reflect statistical learning versus symbol manipulation, and the extent to which such mechanisms change with development. The fine-grained characterizations of infant learning mechanisms that this approach permits should result in a better understanding of the relative contributions of, and the dynamic between, innate and learned factors in language acquisition.     

Pattern induction by infant language learners

How do infants learn the sound patterns of their native language? By the end of the 1st year, infants have acquired detailed aspects of the phonology and phonotactics of their input language. However, the structure of the learning mechanisms underlying this process is largely unknown. In this study, 9-month-old infants were given the opportunity to induce specific phonological patterns in 3 experiments in which syllable structure, consonant voicing position, and segmental position were manipulated. Infants were then familiarized with fluent speech containing words that either fit or violated these patterns. Subsequent testing revealed that infants rapidly extracted new phonological regularities and that this process was constrained such that some regularities were easier to acquire than others.     

Learning about sounds contributes to learning about words: Effects of prosody and phonotactics on infant word learning

This research investigates how early learning about native language sound structure affects how infants associate sounds with meanings during word learning. Infants (19-month-olds) were presented with bisyllabic labels with high or low phonotactic probability (i.e., sequences of frequent or infrequent phonemes in English). The labels were produced with the predominant English trochaic (strong/weak) stress pattern or the less common iambic (weak/strong) pattern. Using the habituation-based Switch Task to test label learning, we found that infants readily learned high probability trochaic labels. However, they failed to learn low probability labels, regardless of stress, and failed to learn iambic labels, regardless of phonotactics. Thus, infants required support from both common phoneme sequences and a common stress pattern to map the labels to objects. These findings demonstrate that early word learning is shaped by prior knowledge of native language phonological regularities and provide support for the role of statistical learning in language acquisition.     

Words in a sea of sounds: the output of infant statistical learning

One of the first problems confronting infant language learners is word segmentation: discovering the boundaries between words. Prior research suggests that 8-month-old infants can detect the statistical patterns that serve as a cue to word boundaries. However, the representational structure of the output of this learning process is unknown. This research assessed the extent to which statistical learning generates novel word-like units, rather than probabilistically-related strings of sounds. Eight-month-old infants were familiarized with a continuous stream of nonsense words with no acoustic cues to word boundaries. A post-familiarization test compared the infants' responses to words versus part-words (sequences spanning a word boundary) embedded either in simple English contexts familiar to the infants (e.g. "I like my tibudo"), or in matched nonsense frames (e.g. "zy fike ny tibudo"). Listening preferences were affected by the context (English versus nonsense) in which the items from the familiarization phase were embedded during testing. A second experiment confirmed that infants can discriminate the simple English contexts and the matched nonsense frames used in Experiment 1. The third experiment replicated the results of Experiment 1 by contrasting the English test frames with non-linguistic frames generated from tone sequences. The results support the hypothesis that statistical learning mechanisms generate word-like units with some status relative to the native language.     

Grammatical pattern learning by human infants and cotton-top tamarin monkeys

There is a surprising degree of overlapping structure evident across the languages of the world. One factor leading to cross-linguistic similarities may be constraints on human learning abilities. Linguistic structures that are easier for infants to learn should predominate in human languages. If correct, then (a) human infants should more readily acquire structures that are consistent with the form of natural language, whereas (b) non-human primates' patterns of learning should be less tightly linked to the structure of human languages. Prior experiments have not directly compared laboratory-based learning of grammatical structures by human infants and non-human primates, especially under comparable testing conditions and with similar materials. Five experiments with 12-month-old human infants and adult cotton-top tamarin monkeys addressed these predictions, employing comparable methods (familiarization-discrimination) and materials. Infants rapidly acquired complex grammatical structures by using statistically predictive patterns, failing to learn structures that lacked such patterns. In contrast, the tamarins only exploited predictive patterns when learning relatively simple grammatical structures. Infant learning abilities may serve both to facilitate natural language acquisition and to impose constraints on the structure of human languages.     

汉语声调水平映射规则的内隐学习及其长度迁移效应

内隐学习领域关注的重要问题是被试能够习得何种结构及其相应的学习机制。远距离规则的研究为澄清这一问题提供了新的视角。现有研究已证实被试能够内隐地习得并迁移固定长度的远距离规则。按照内隐学习抽象性的观点,如果被试习得的是远距离的抽象规则本身,那么迁移也同时会发生在不同长度的材料上。因此,研究以独特的汉语声调水平映射规则为材料,通过对表面特征与底层规则之间的分离操作,探讨声调水平映射规则的内隐习得和长度迁移,结果表明被试不仅能够习得这一规则,还能够将该规则灵活迁移到不同长度的材料上,进一步为内隐学习的抽象性特点和无限性的学习机制提供强有力的新证据。     

The intersensory origins of word‐comprehension: an ecological–dynamic systems view

How do infants begin to understand spoken words? Recent research suggests that word comprehension develops from the early detection of intersensory relations between conventionally paired auditory speech patterns (words) and visible objects or actions. More importantly, in keeping with dynamic systems principles, the findings suggest that word comprehension develops from a dynamic and complementary relationship between the organism (the infant) and the environment (language addressed to the infant). In addition, parallel findings from speech and non‐speech studies of intersensory perception provide evidence for domain general processes in the development of word comprehension. These research findings contrast with the view that a lexical acquisition device with specific lexical principles and innate constraints is required for early word comprehension. Furthermore, they suggest that learning of word–object relations is not merely an associative process. The data support an alternative view of the developmental process that emphasizes the dynamic and reciprocal interactions between general intersensory perception, selective attention and learning in infants, and the specific characteristics of maternal communication.     

Contrasting behavioral looking procedures: a case study on infant speech segmentation

This paper compared three different procedures common in infant speech perception research: a headturn preference procedure (HPP) and a central-fixation (CF) procedure with either automated eye-tracking (CF-ET) or manual coding (CF-M). In theory, such procedures all measure the same underlying speech perception and learning mechanisms and the choice between them should ideally be irrelevant in unveiling infant preference. However, the ManyBabies study (ManyBabies Consortium, 2019), a cross-laboratory collaboration on infants’ preference for child-directed speech, revealed that choice of procedure can modulate effect sizes. Here we examined whether procedure also modulates preference in paradigms that add a learning phase prior to test: a speech segmentation paradigm. Such paradigms are particularly important for studying the learning mechanisms infants can employ for language acquisition. We carried out the same familiarization-then-test experiment with the three different procedures (32 unique infants per procedure). Procedures were compared on various factors, such as overall effect, average looking time and drop-out rate. The key observations are that the HPP yielded a larger familiarity preference, but also reported larger drop-out rates. This raises questions about the generalizability of results. We argue that more collaborative research into different procedures in infant preference experiments is required in order to interpret the variation in infant preferences more accurately.     

Co‐occurrence statistics as a language‐dependent cue for speech segmentation

To what extent can language acquisition be explained in terms of different associative learning mechanisms? It has been hypothesized that distributional regularities in spoken languages are strong enough to elicit statistical learning about dependencies among speech units. Distributional regularities could be a useful cue for word learning even without rich language‐specific knowledge. However, it is not clear how strong and reliable the distributional cues are that humans might use to segment speech. We investigate cross‐linguistic viability of different statistical learning strategies by analyzing child‐directed speech corpora from nine languages and by modeling possible statistics‐based speech segmentations. We show that languages vary as to which statistical segmentation strategies are most successful. The variability of the results can be partially explained by systematic differences between languages, such as rhythmical differences. The results confirm previous findings that different statistical learning strategies are successful in different languages and suggest that infants may have to primarily rely on non‐statistical cues when they begin their process of speech segmentation.     

Rules vs. analogy in English past tenses: a computational/experimental study

Are morphological patterns learned in the form of rules? Some models deny this, attributing all morphology to analogical mechanisms. The dual mechanism model (Pinker, S., & Prince, A. (1998). On language and connectionism: analysis of a parallel distributed processing model of language acquisition. Cognition, 28, 73-193) posits that speakers do internalize rules, but that these rules are few and cover only regular processes; the remaining patterns are attributed to analogy. This article advocates a third approach, which uses multiple stochastic rules and no analogy. We propose a model that employs inductive learning to discover multiple rules, and assigns them confidence scores based on their performance in the lexicon. Our model is supported over the two alternatives by new "wug test" data on English past tenses, which show that participant ratings of novel pasts depend on the phonological shape of the stem, both for irregulars and, surprisingly, also for regulars. The latter observation cannot be explained under the dual mechanism approach, which derives all regulars with a single rule. To evaluate the alternative hypothesis that all morphology is analogical, we implemented a purely analogical model, which evaluates novel pasts based solely on their similarity to existing verbs. Tested against experimental data, this analogical model also failed in key respects: it could not locate patterns that require abstract structural characterizations, and it favored implausible responses based on single, highly similar exemplars. We conclude that speakers extend morphological patterns based on abstract structural properties, of a kind appropriately described with rules.