Intersensory Redundancy and 7‐Month‐Old Infants' Memory for Arbitrary Syllable‐Object Relations

Seven‐month‐old infants require redundant information, such as temporal synchrony, to learn arbitrary syllable‐object relations (Gogate & Bahrick, 1998). Infants learned the relations between 2 spoken syllables, /a/ and /i/, and 2 moving objects only when temporal synchrony was present during habituation. This article presents 2 experiments to address infants' memory for these relations. In Experiment 1, infants remembered the syllable‐object relations after 10 min, only when temporal synchrony between the vocalizations and moving objects was provided during learning. In Experiment 2, 7‐month‐olds were habituated to the same syllable‐object pairs in the presence of temporal synchrony and tested for memory after 4 days. Once again, infants learned and showed emerging memory for the syllable‐object relations 4 days after original learning under the temporally synchronous condition. These findings are consistent with the view that prior to symbolic development, infants learn and remember word‐object relations by perceiving redundant information in the vocal and gestural communication of adults.     

From Syllables to Syntax: Multilevel Statistical Learning by 12‐Month‐Old Infants

To successfully acquire language, infants must be able to track multiple levels of regularities in the input. In many cases, regularities only emerge after some learning has already occurred. For example, the grammatical relationships between words are only evident once the words have been segmented from continuous speech. To ask whether infants can engage in this type of learning process, 12‐month‐old infants in 2 experiments were familiarized with multiword utterances synthesized as continuous speech. The words in the utterances were ordered based on a simple finite‐state grammar. Following exposure, infants were tested on novel grammatical and ungrammatical sentences. The results indicate that the infants were able to perform 2 statistical learning tasks in sequence: first segmenting the words from continuous speech, and subsequently discovering the permissible orderings of the words. Given a single set of input, infants were able to acquire multiple levels of structure, suggesting that multiple levels of representation (initially syllable‐level combinations, subsequently word‐level combinations) can emerge during the course of learning.     

Word Segmentation in Monolingual Infants Acquiring Canadian English and Canadian French: Native Language,Cross‐Dialect,and Cross‐Language Comparisons

In five experiments, we tested segmentation of word forms from natural speech materials by 8‐month‐old monolingual infants who are acquiring Canadian French or Canadian English. These two languages belong to different rhythm classes; Canadian French is syllable‐timed and Canada English is stress‐timed. Findings of Experiments 1, 2, and 3 show that 8‐month‐olds acquiring either Canadian French or Canadian English can segment bi‐syllable words in their native language. Thus, word segmentation is not inherently more difficult in a syllable‐timed compared to a stress‐timed language. Experiment 4 shows that Canadian French‐learning infants can segment words in European French. Experiment 5 shows that neither Canadian French‐ nor Canadian English‐learning infants can segment two syllable words in the other language. Thus, segmentation abilities of 8‐month‐olds acquiring either a stress‐timed or syllable‐timed language are language specific.     

Chinese and English Infants' Tone Perception: Evidence for Perceptual Reorganization

Over half the world's population speaks a tone language, yet infant speech perception research has typically focused on consonants and vowels. Very young infants can discriminate a wide range of native and nonnative consonants and vowels, and then in a process of perceptual reorganization over the 1st year, discrimination of most nonnative speech sounds deteriorates. We investigated perceptual reorganization for tones by testing 6‐ and 9‐month‐old infants from tone (Chinese) and nontone (English) language environments for speech (lexical tone) and nonspeech (violin sound) tone discrimination in both cross‐sectional and longitudinal studies. Overall, Chinese infants performed equally well at 6 and 9 months for both speech and nonspeech tone discrimination. Conversely, English infants' discrimination of lexical tone declined between 6 and 9 months of age, whereas their nonspeech tone discrimination remained constant. These results indicate that the reorganization of tone perception is a function of the native language environment, and that this reorganization is linguistically based. Supplementary materials to this article are available on the World Wide Web at http:www.infancyarchives.com     

Age‐Related Changes in Prosodic Features of Maternal Speech to Prelingually Deaf Infants with Cochlear Implants

This study investigated prosodic and structural characteristics of infant‐directed speech to hearing‐impaired infants as they gain hearing experience with a cochlear implant over a 12‐month period of time. Mothers were recorded during a play interaction with their HI infants (N = 27, mean age 18.4 months) at 3, 6, and 12 months postimplantation. Two separate control groups of mothers with age‐matched normal‐hearing infants (NH‐AM) (N = 21, mean age 18.1 months) and hearing experience‐matched normal‐hearing infants (NH‐EM) (N = 24, mean age 3.1 months) were recorded at three testing sessions. Mothers produced less exaggerated pitch characteristics, a larger number of syllables per utterance, and faster speaking rate when interacting with NH‐AM as compared to HI infants. Mothers also produced more syllables and demonstrated a trend suggesting faster speaking rate in speech to NH‐EM relative to HI infants. Age‐related modifications included decreased pitch standard deviation and increased number of syllables in speech to NH‐AM infants and increased number of syllables in speech to HI and NH‐EM infants across the 12‐month period. These results suggest that mothers are sensitive to the hearing status of their infants and modify characteristics of infant‐directed speech over time.     

Picture Perception in Infants: Generalization From Two‐Dimensional to Three‐Dimensional Displays

Two experiments investigated 9‐month‐old infants’ abilities to recognize the correspondence between an actual three‐dimensional (3D) object and its two‐dimensional (2D) representation, looking specifically at representations that did not literally depict the actual object: schematic line drawings. In Experiment 1 , infants habituated to a line drawing of either a doll or a sheep and were then tested with the actual objects themselves. Infants habituated to the sheep drawing recovered to the unfamiliar but not the familiar object, showing a novelty preference. Infants habituated to the doll drawing, however, recovered to both familiar and unfamiliar objects, failing to show any preference between the two. In Experiment 2 , infants habituated to the 3D objects and were then tested with the 2D line drawings. In this case, both groups of infants showed a preference only for the novel displays. Together these findings demonstrate that 9‐month‐old infants recognize the correspondence between 3D objects and their 2D representations, even when these representations are not literal copies of the objects themselves.     

English‐Learning Infants' Representations of Word Forms With Iambic Stress

Retaining detailed representations of unstressed syllables is a logical prerequisite for infants' use of probabilistic phonotactics to segment iambic words from fluent speech. The head‐turn preference study was used to investigate the nature of English‐learners' representations of iambic word onsets. Fifty‐four 10.5‐month‐olds were familiarized to passages containing the nonsense iambic word forms ginome and tupong. Following familiarization, infants were either tested on familiar (ginome and tupong) or near‐familiar (pinome and bupong) versus unfamiliar (kidar and mafoos) words. Infants in the familiar test group (familiar vs. unfamiliar) oriented significantly longer to familiar than unfamiliar test items, whereas infants in the near‐familiar test group (near‐familiar vs. unfamiliar) oriented equally long to near‐familiar and unfamiliar test items. Our results provide evidence that infants retain fairly detailed representations of unstressed syllables and therefore support the hypothesis that infants use phonotactic cues to find words in fluent speech.     

Hierarchical Processing in Seven‐Month‐Old Infants

Hierarchical structures are crucial to many aspects of cognitive processing and especially for language. However, there still is little experimental support for the ability of infants to learn such structures. Here, we show that, with structures simple enough to be processed by various animals, seven‐month‐old infants seem to learn hierarchical relations. Infants were presented with an artificial language composed of “sentences” made of three‐syllable “words.” The syllables within words conformed to repetition patterns based on syllable tokens involving either adjacent repetitions (e.g., dubaba) or nonadjacent repetitions (e.g., du ba du ) . Importantly, the sequence of word structures in each sentence conformed to repetition patterns based on word types (e.g., aba‐ abb ‐ abb ). Infants learned this repetition pattern of repetition patterns and thus likely a hierarchical pattern based on repetitions, but only when the repeated word structure was based on adjacent repetitions. While our results leave open the question of which exact sentence‐level pattern infants learned, they suggest that infants embedded the word‐level patterns into a higher‐level pattern and thus seemed to acquire a hierarchically embedded pattern.     

Evidence of the Face Inversion Effect in 4‐Month‐Old Infants

This study tested the presence of the face inversion effect in 4‐month‐old infants using habituation to criterion followed by a novelty preference paradigm. Results of Experiment 1 confirmed previous findings, showing that when 1 single photograph of a face is presented in the habituation phase and when infants are required to recognize the same photograph, no differences in recognition performance with upright and inverted faces are found. However, Experiment 2 showed that, when infants are habituated to a face shown in a variety of poses and are required to recognize a new pose of the same face, infants' recognition performances were higher for upright than for inverted faces. Overall, results indicate that, under some experimental conditions, 4‐month‐olds process faces differently according to whether faces are presented upright or inverted.     

Changes in Preference for Infant‐Directed Speech in Low and Moderate Noise by 4.5‐ to 13‐Month‐Olds

Although a large literature discusses infants' preference for infant‐directed speech (IDS), few studies have examined how this preference might change over time or across listening situations. The work reported here compares infants' preference for IDS while listening in a quiet versus a noisy environment, and across 3 points in development: 4.5 months of age, 9 months of age, and 13 months of age. Several studies have suggested that IDS might help infants to pick out speech in the context of noise (Colombo, Frick, Ryther, Coldren, & Mitchell, 1995; Fernald, 1984; Newman, 2003); this might suggest that infants' preference for IDS would increase in these settings. However, this was not found to be the case; at all 3 ages, infants showed similar advantage (or lack thereof) for IDS as compared to adult‐directed speech when presented in noise versus silence. There was, however, a significant interaction across ages: Infants aged 4.5 months showed an overall preference for IDS, whereas older infants did not, despite listening to the same stimuli. The lack of an effect with older infants replicates and extends recent findings by Hayashi, Tamekawa, and Kiritani (2001), suggesting that the variations in fundamental frequency and affect are not sufficient cues to IDS for older infants.     

Six‐month‐old infants recognize phrases in song and speech

Infants exploit acoustic boundaries to perceptually organize phrases in speech. This prosodic parsing ability is well‐attested and is a cornerstone to the development of speech perception and grammar. However, infants also receive linguistic input in child songs. This study provides evidence that infants parse songs into meaningful phrasal units and replicates previous research for speech. Six‐month‐old Dutch infants (n = 80) were tested in the song or speech modality in the head‐turn preference procedure. First, infants were familiarized to two versions of the same word sequence: One version represented a well‐formed unit, and the other contained a phrase boundary halfway through. At test, infants were presented two passages, each containing one version of the familiarized sequence. The results for speech replicated the previously observed preference for the passage containing the well‐formed sequence, but only in a more fine‐grained analysis. The preference for well‐formed phrases was also observed in the song modality, indicating that infants recognize phrase structure in song. There were acoustic differences between stimuli of the current and previous studies, suggesting that infants are flexible in their processing of boundary cues while also providing a possible explanation for differences in effect sizes.     

A Cross‐Linguistic Study of Word‐Mapping in 18‐ to 20‐Month‐Old Infants

This study was designed to examine whether infants acquiring languages that place a differential emphasis on nouns and verbs, focus their attention on motions or objects in the presence of a novel word. An infant‐controlled habituation paradigm was used to teach 18‐ to 20‐month‐old English‐, French‐, and Japanese‐speaking infants’ novel words for events. Infants were habituated to two word‐event pairings and then presented with new combinations that involved a familiar word with a new object or motion, or both. Children could map the novel word to both the object and the motion, despite the differential salience of object and motion words in their native language. A control experiment with no label confirmed that both object and motion changes were detectable.     

The Relationship Between Processing Facial Identity and Emotional Expression in 8‐Month‐Old Infants

In Experiment 1, it was investigated whether infants process facial identity and emotional expression independently or in conjunction with one another. Eight‐month‐old infants were habituated to two upright or two inverted faces varying in facial identity and emotional expression. Infants were tested with a habituation face, a switch face, and a novel face. In the switch faces, a new combination of identity and emotional expression was presented. The results show that infants differentiated between switch and habituation faces only in the upright condition but not in the inverted condition. Experiment 2 provides evidence that infants’ nonresponse in the inverted condition can be attributed to their independent processing of facial identity and emotional expression. This suggests that infants in the upright condition processed facial identity and emotional expression in conjunction with one another.     

Crawling is Associated with Mental Rotation Ability by 9‐Month‐Old Infants

The present experiment examined whether 9‐month‐old infants’ mental rotation ability was related to their crawling ability. Forty‐eight 9‐month‐old infants were tested; half of them crawled for 7.1 weeks on average. Infants were habituated to a video of a simplified Shepard–Metzler object rotating back and forth through a 240° angle around the longitudinal axis of the object. Infants were tested with videos of the same object rotating through the previously unseen 120° angle and with the mirror image of that display. The results showed that the crawlers looked significantly longer at the mirror object than at the familiar object. The results support the interpretation that crawling experience is associated with 9‐month‐old infants’ mental rotation ability.     

Distributional Phonetic Learning at 10 Months of Age

Infant phonetic perception reorganizes in accordance with the native language by 10 months of age. One mechanism that may underlie this perceptual change is distributional learning, a statistical analysis of the distributional frequency of speech sounds. Previous distributional learning studies have tested infants of 6–8 months, an age at which native phonetic categories have not yet developed. Here, three experiments test infants of 10 months to help illuminate perceptual ability following perceptual reorganization. English‐learning infants did not change discrimination in response to nonnative speech sound distributions from either a voicing distinction (Experiment 1) or a place‐of‐articulation distinction (Experiment 2). In Experiment 3, familiarization to the place‐of‐articulation distinction was doubled to increase the amount of exposure, and in this case infants began discriminating the sounds. These results extend the processes of distributional learning to a new phonetic contrast, and reveal that at 10 months of age, distributional phonetic learning remains effective, but is more difficult than before perceptual reorganization.     

Sensitivity to Word‐Final Phonotactics in 9‐ to 16‐Month‐Old Infants

Previous research has shown that infants begin to display sensitivities to language‐specific phonotactics and probabilistic phonotactics at around 9 months of age. However, certain phonotactic patterns have not yet been examined, such as contrast neutralization, in which phonemic contrasts are neutralized typically in syllable‐ or word‐final position. Thus, the acquisition of contrast neutralization is dependent on infants' ability to perceive certain contrasts in final position. The studies reported here test infants' sensitivity to voicing neutralization in word‐final position and infants' discrimination of voicing and place of articulation (POA) contrasts in word‐initial and word‐final position. Nine and 11‐month‐old Dutch‐learning infants showed no preference for legal versus illegal voicing phonotactics that were contrasted in word‐final position. Furthermore, 10‐month‐old infants showed no discrimination of voicing or POA contrasts in word‐final position, whereas they did show sensitivity to the same contrasts in word‐initial position. By 16 months, infants were able to discriminate POA contrasts in word‐final position, although showing no discrimination of the word‐final voicing contrast. These findings have broad implications for models of how learners acquire the phonological structures of their language, for the types of phonotactic structures to which infants are presumed to be sensitive, and for the relative sensitivity to phonemic distinctions by syllable and word position during acquisition.     

2‐Year‐Olds’ Speech Understanding in Multitalker Environments

Infants and toddlers are often spoken to in the presence of background sounds, including speech from other talkers. Prior work has suggested that infants 1 year of age and younger can only recognize speech when it is louder than any distracters in the environment. The present study tests 24‐month‐olds’ ability to understand speech in a multitalker environment. Children were presented with a preferential‐looking task in which a target voice told them to find one of two objects. At the same time, multitalker babble was presented as a distracter, at one of four signal‐to‐noise ratios. Children showed some ability to understand speech and look at the appropriate referent at signal‐to‐noise ratios as low as ?5 dB. These findings suggest that 24‐month‐olds are better able to selectively attend to an interesting voice in the context of competing distracter voices than are younger infants. There were significant correlations between individual children’s performance and their vocabulary size, but only at one of the four noise levels; thus, it does not appear that vocabulary size is the driving factor in children’s listening improvement, although it may be a contributing factor to performance in noisy environments.     

Perception of Similar and Dissimilar Lexical Tones by Non‐Tone‐Learning Infants

This study examined the perception of Mandarin lexical tones by non‐tone‐learning infants. We tested French‐learning 4‐, 8‐, and 11‐month‐olds on Tone 2 (rising) versus Tone 3 (dipping), the most acoustically similar contrast in Mandarin, and on Tone 1 (high) versus Tone 4 (falling), acoustically more dissimilar contrast. We hypothesized that sensitivity should decline with age for the similar contrast, and the dissimilar contrast should remain more discriminable. Infants were habituated to one tone and tested with the same tone versus the contrastive tone. Results showed that the dissimilar T1–T4 contrast was consistently discriminated by all three ages, whereas the discrimination of the similar T2–T3 contrast revealed a tendency to decline over the ages. These results suggest that relative to consonants and vowels, perceptual sensitivity to lexical tones remains stronger in non‐tone‐learning infants. Discrimination of lexical tones is affected by both acoustic salience and perceptual attunement to the native‐language phonology.     

Stress Pattern Preference in Spanish‐Learning Infants: The Role of Syllable Weight

As a result of exposure, infants acquire biases that conform to the rhythmic properties of their native language. Previous lexical stress preference studies have shown that English‐ and German‐, but not French‐learning infants, show a bias toward trochaic words. The present study explores Spanish‐learning infants' lexical stress preferential patterns and the role of syllable weight at 9 months of age. Spanish is a syllable‐timed language with no vowel reduction and variable stress. Around 50% of the word types in Spanish are disyllabic, with a superior proportion of trochees than iambs (60% and 40%, respectively). Experiment 1 with CV.CV pseudo‐words failed to reveal a clear trochaic bias in 9‐month‐old Spanish‐learning infants. However, when preference was explored with items containing a heavy syllable (CVC.CV and CV.CVC, respectively), both a trochaic (Experiment 2) and an iambic preference (Experiment 3) could be elicited. These results suggest that knowledge about the close and highly regular link between heavy syllables and stress assignment in Spanish can be easily acquired and determines infants' preference at 9 months of age, while for CV.CV items, the trochaic bias appears to be weak. Our results broaden the current knowledge on the factors that determine the emergence of rhythmic biases.     

Infant‐Directed Speech Facilitates Word Segmentation

There are reasons to believe that infant‐directed (ID) speech may make language acquisition easier for infants. However, the effects of ID speech on infants' learning remain poorly understood. The experiments reported here assess whether ID speech facilitates word segmentation from fluent speech. One group of infants heard a set of nonsense sentences spoken with intonation contours characteristic of adult‐directed (AD) speech, and the other group heard the same sentences spoken with intonation contours characteristic of ID speech. In both cases, the only cue to word boundaries was the statistical structure of the speech. Infants were able to distinguish words from syllable sequences spanning word boundaries after exposure to ID speech but not after hearing AD speech. These results suggest that ID speech facilitates word segmentation and may be useful for other aspects of language acquisition as well. Issues of direction of preference in preferential listening paradigms are also considered.