Rushen Shi

Newborn infants’ sensitivity to perceptual cues to lexical and grammatical words

In our study newborn infants were presented with lists of lexical and grammatical words prepared from natural maternal speech. The results show that newborns are able to categorically discriminate these sets of words based on a constellation of perceptual cues that distinguish them. This general ability to detect and categorically discriminate sets of words on the basis of multiple acoustic and phonological cues may provide a perceptual base that can help older infants bootstrap into the acquisition of grammatical categories and syntactic structure.

Frequency and form as determinants of functor sensitivity in English-acquiring infants

High-frequency functors are arguably among the earliest perceived word forms and may assist extraction of initial vocabulary items. Canadian 11- and 8-month-olds were familiarized to pseudo-nouns following either a high-frequency functor the or a low-frequency functor her versus phonetically similar mispronunciations of each, kuh and ler, and then tested for recognition of the pseudo-nouns. A preceding the (but not kuh, her, ler) facilitated extraction of the pseudo-nouns for 11-month-olds; the is thus well-specified in form for these infants. However, both the and kuh (but not her-ler) facilitated segmentation for 8-month-olds, suggesting an initial underspecified representation of high-frequency functors.

Six-Month-Old Infants' Preference for Lexical Words

Previous work has shown that newborn infants categorically discriminate the fundamental syntactic category distinction between lexical and grammatical words. In this article, we show that by the age of 6 months, infants prefer to listen to lexical over grammatical words. In Experiment 1, infants were habituated to a list of either lexical or grammatical words, and then tested on new lists of words from the same and the contrasting categories. The infants showed recovery to lexical words after habituation to grammatical words but not vice versa. This asymmetry indicates a possible preference for lexical words. In Experiments 2 and 3, preference was assessed directly by presenting infants with alternating trials of lexical and grammatical words, in the central-fixation preference procedure. The infants looked significantly longer during lexical-word than grammatical-word trials. These results show that by 6 months, infants attend preferentially to lexical words. The implications of this emerging attentional preference for subsequent language acquisition are discussed.

The basis of preference for lexical words in 6-month-old infants

Six-month-old English-learning infants have been shown to prefer English lexical over English grammatical words. The preference is striking because there are few grammatical words in total number but each occurs far more frequently in input speech than any individual lexical word. This could be because lexical words are universally more salient and interesting acoustic and phonological forms than are grammatical words. Alternatively, familiarity may play a role since infants may know some specific lexical words. Here we explore the first possibility by testing Chinese-learning infants’ response to English lexical and grammatical words. These infants, who had virtually no prior exposure to English and thus were unfamiliar with any English words, nevertheless preferred to listen to English lexical words, as in the case of English-learning infants. This finding increases the plausibility that it is the acoustic and phonological salience of lexical words that determines the preference for lexical words in infants.

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.

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.

Recognition of function words in 8‐month‐old French‐learning infants

Previous work has shown that German‐learning 7‐9‐month‐old infants recognize function words (Hoehle and Weissenborn, 2003). English‐learning infants recognize function words around 10.5‐11 months (Schafer et al. 1998; Shady, 1996; Shi et al., 2003, 2004), and the highly frequent determiner ‘‘the’’ at 8 months (Shi et al., 2004). The present study investigates French‐learning infants’ recognition of function words. As French is a syllable‐timing language, the fuller syllabic status may allow infants to recognize function words earlier than English‐learning infants. Syntactically and morphologically, functional elements occur more systematically in French than in English, providing reliable statistical cues to functor segmentation. Using a preferential looking procedure, we familiarized 8‐month‐olds with a target function word (‘‘des,’’ ‘‘la,’’ ‘‘mes’’ or ‘‘ta’’), and tested them with phrases containing the target versus a non‐target. Results showed that infants’ looking time to the phrases containing the t...

Simulating the acquisition of lexical tones from continuous dynamic input

Infants develop phonetic categories by simply being exposed to adult speech. It remains unclear, however, how they handle the extensive variability inherent to speech, and how they process multiple linguistic functions that share the same acoustic parameters. Across four neural network simulations of lexical tone acquisition, self-organizing maps were trained with continuous speech input of increasing variability. Robust tonal categorization was achieved by tracking the velocity profiles of fundamental frequency contours. This result suggests that continuous speech signal carries sufficient categorical information that can be directly processed, and that dynamic acoustic information can be used for resolving the variability problem.

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.

Infant‐directed speech: Final syllable lengthening and rate of speech

Speech rate has been reported to be slower in infant‐directed speech (IDS) than in adult‐directed speech (ADS). Studies have also found phrase‐final lengthening to be more exaggerated in IDS compared with ADS. In our study we asked whether the observed overall slower rate of IDS is due to exaggerated utterance‐final syllable lengthening. Two mothers of preverbal English‐learning infants each participated in two recording sessions, one with her child, and another with an adult friend. The results showed an overall slower rate in IDS compared to ADS. However, when utterance‐final syllables were excluded from the calculation, the speech rate in IDS and ADS did not differ significantly. The duration of utterance‐final syllables differed significantly for IDS versus ADS. Thus, the overall slower rate of IDS was due to the extra‐long final syllable occurring in relatively short utterances. The comparable pre‐final speech rate for IDS and ADS further accentuates the final syllable lengthening in IDS. As utterances in IDS are typically phrases or clauses, the particularly strong final‐lengthening cue could potentially facilitate infants’ segmentation of these syntactic units. These findings are consistent with the existing evidence that pre‐boundary lengthening is important in the processing of major syntactic units in English‐learning infants.