Baby's Online Live Database: An Open Platform for Developmental Science.

Efficient data collection in developmental studies is facing challenges due to the decreased birth rates in many regions, reproducibility problems in psychology research, and the COVID-19 pandemic. Here, we propose a novel platform for online developmental science research, the Baby's Online Live Database (BOLD), which extends the scope of the accessible participant pool, simplifies its management, and enables participant recruitment for longitudinal studies. Through BOLD, researchers can conduct online recruitment of participants preregistered to BOLD simply by specifying their attributes, such as gender and age, and direct the participants to dedicated webpages for each study. Moreover, BOLD handles participant recruitment and reward payment, thereby freeing researchers from the labor of participant management. BOLD also allows researchers the opportunity to access data that were collected from participants in previous research studies. This enables researchers to carry out longitudinal analyses at a relatively low cost. To make BOLD widely accessible, a consortium was formed within the Japan Society of Baby Science, where members from diverse research groups discussed the blueprint of this system. Once in full-scaled operation, BOLD is expected to serve as a platform for various types of online studies and facilitate international collaboration among developmental scientists in the near future.

Are higher-frequency sounds brighter in color and smaller in size? Auditory-visual correspondences in 10-month-old infants.

Previous research has shown that not only adults but also two-and-a-half-year-old children associate higher-frequency sounds with smaller objects and with objects of brighter colors, suggesting that these intersensory correspondences are based on neural connections present very early in life. The present research examined whether 10-month olds are sensitive to these intersensory correspondences using a violation-of-expectation procedure. The results of Experiment 1 indicated that 10-month-olds associate a higher-frequency tone with an object of a brighter color and a lower-frequency tone with an object of a darker color. However, Experiment 2 found that 10-month olds did not always associate a higher-frequency tone with a smaller object and a lower-frequency tone with a larger object. The results suggest that infants have an initial bias to associate pitch with brightness, whereas pitch-size correspondences may be learned after birth by observing statistical co-occurrence patterns in the real world.

Now you hear it, now you don't: vowel devoicing in Japanese infant-directed speech.

In this work, we examine a context in which a conflict arises between two roles that infant-directed speech (IDS) plays: making language structure salient and modeling the adult form of a language. Vowel devoicing in fluent adult Japanese creates violations of the canonical Japanese consonant-vowel word structure pattern by systematically devoicing particular vowels, yielding surface consonant clusters. We measured vowel devoicing rates in a corpus of infant- and adult-directed Japanese speech, for both read and spontaneous speech, and found that the mothers in our study preserve the fluent adult form of the language and mask underlying phonological structure by devoicing vowels in infant-directed speech at virtually the same rates as those for adult-directed speech. The results highlight the complex interrelationships among the modifications to adult speech that comprise infant-directed speech, and that form the input from which infants begin to build the eventual mature form of their native language.

Infant Discrimination of a Morphologically Relevant Word-Final Contrast.

Six-, 12-, and 18-month-old English-hearing infants were tested on their ability to discriminate nonword forms ending in the final stop consonants /k/ and /t/ from their counterparts with final /s/ added, resulting in final clusters /ks/ and /ts/, in a habituation-dishabituation, looking time paradigm. Infants at all 3 ages demonstrated an ability to discriminate this type of contrast, a contrast that constitutes one phonetic cue for the English morphological concepts of plural, possession, and person. These results suggest that across a significant portion of the development of infants' speech perception, this type of final contrast is discriminable.

Age-related changes in sensitivity to native phonotactics in Japanese infants.

Japanese infants at the ages of 6, 12, and 18 months were tested on their ability to discriminate three nonsense words with different phonotactic status: canonical keetsu, noncanonical but possible keets, and noncanonical and impossible keet. The results showed that 12 and 18 months olds discriminate the keets/keetsu pair, but infants in all age groups fail to discriminate the keets/keet pair. Taken together with the findings in our previous study [Kajikawa et al., J. Acoust. Soc. Am. 120(4), 2278-2284 (2006)], these results suggest that Japanese infants develop the perceptual sensitivity for native phonotactics after 6 months of age, and that this sensitivity is limited to canonical patterns at this early developmental stage.

Infant-directed speech supports phonetic category learning in English and Japanese.

Across the first year of life, infants show decreased sensitivity to phonetic differences not used in the native language [Werker, J. F., & Tees, R. C. (1984). Cross-language speech perception: evidence for perceptual reorganization during the first year of life. Infant Behaviour and Development, 7, 49-63]. In an artificial language learning manipulation, Maye, Werker, and Gerken [Maye, J., Werker, J. F., & Gerken, L. (2002). Infant sensitivity to distributional information can affect phonetic discrimination. Cognition, 82(3), B101-B111] found that infants change their speech sound categories as a function of the distributional properties of the input. For such a distributional learning mechanism to be functional, however, it is essential that the input speech contain distributional cues to support such perceptual learning. To test this, we recorded Japanese and English mothers teaching words to their infants. Acoustic analyses revealed language-specific differences in the distributions of the cues used by mothers (or cues present in the input) to distinguish the vowels. The robust availability of these cues in maternal speech adds support to the hypothesis that distributional learning is an important mechanism whereby infants establish native language phonetic categories.

Cross-language sensitivity to phonotactic patterns in infants.

This study explored sensitivity to word-level phonotactic patterns in English and Japanese monolingual infants. Infants at the ages of 6, 12, and 18 months were tested on their ability to discriminate between test words using a habituation-switch experimental paradigm. All of the test words, neek, neeks, and neekusu, are phonotactically legitimate for English, whereas the first two words are critically noncanonical in Japanese. The language-specific phonotactical congruence influenced infants' performance in discrimination. English-learning infants could discriminate between neek and neeks at the age of 18 months, but Japanese infants could not. There was a similar developmental pattern for infants of both language groups for discrimination of neek and neeks, but Japanese infants showed a different trajectory from English infants for neekusu/neeks. These differences reflect the different status of these word patterns with respect to the phonotactics of both languages, and reveal early sensitivity to subtle phonotactic and language input patterns in each language.

Japanese listeners' perceptions of phonotactic violations.

The canonical form for Japanese words is (Consonant)Vowel(Consonant) Vowel-. However, a regular process of high vowel devoicing between voiceless consonants and word-finally after voiceless consonants results in consonant clusters and word-final consonants, apparent violations of that phonotactic pattern. We investigated Japanese adults' perceptions of these violations, asking them to rate both canonical and noncanonical nonsense forms on a scale of goodness. Results indicate that adults show evidence of being guided in making their judgments by an implicit understanding of both typical canonical forms and appropriate contexts for vowel devoicing.

Speech overlap in Japanese mother-child conversations.

This study aimed to clarify the development of conversational style in Japanese mother-child interactions. We focused on the frequency of speech overlap as an index of Japanese conversational style, with particular attention to ne, a particle produced by the speaker, and to backchannels, such as 'uh-huh', produced by the listener that support sympathetic conversation. The results of longitudinal observations of two Japanese mother-child dyads from approximately 0;11 to 3;3 suggest that an adultlike conversational style with frequent overlaps emerges in Japanese child-directed speech around the two-word utterance period, and a child's development of ne use is closely related to this shift.

[Recognition of sound pattern of words extracted from spoken sentences by preverbal infants].

The present experiment investigated the ability of recognition and long-term retention of sound pattern of words extracted from spoken sentences in preverbal infants. When preferences of 8-month-old Japanese infants for target words and for novel words were tested by head-turn preference procedure, immediately after being auditory exposed to spoken sentences that included the target words, they showed preference for target words significantly over novel words. They were able to recognize words that were presented within sentences previously. Moreover, such preference was confirmed when the infants were tested with a 2-week interval. On the other hand, their preference for prosodic properties of the exposed spoken sentences was not confirmed. Infants retain information of those words that were extracted from the speech analytically rather than holistically.