Impact of talker variability on language development in two-year-olds.

This research investigated the impact of the number of talkers with whom children engage in daily conversation on their language development. Two surveys were conducted in 2020, targeting two-year-olds growing up in Japanese monolingual families. Caregivers reported the number of talkers in three age groups and children's productive vocabulary via questionnaires. The results demonstrated significant effects of variability in talkers in fifth grade or above in Study 1 (N = 50; male = 23; r = .372) and in adult talkers in Study 2 (N = 175; non-nursery going; male = 76; r = .184) on children's vocabulary development, after controlling for language exposure time and demographic variables. Possible mediating factors are discussed. This research extends previous findings from immigrant bilingual children to monolingual speakers in Japan, suggesting the potential contribution of available talkers other than caregivers in conversational environments.

Preschoolers' Development of Theory of Mind: The Contribution of Understanding Psychological Causality in Stories.

This study investigated the relationship between children's abilities to understand causal sequences and another's false belief. In Experiment 1, we tested 3-, 4-, 5-, and 6-year-old children (n = 28, 28, 27, and 27, respectively) using false belief and picture sequencing tasks involving mechanical, behavioral, and psychological causality. Understanding causal sequences in mechanical, behavioral, and psychological stories was related to understanding other's false beliefs. In Experiment 2, children who failed the initial false belief task (n = 50) were reassessed 5 months later. High scorers in the sequencing of the psychological stories in Experiment 1 were more likely to pass the standard false belief task than were the low scorers. Conversely, understanding causal sequences in the mechanical and behavioral stories in Experiment 1 did not predict passing the false belief task in Experiment 2. Thus, children may understand psychological causality before they are able to use it to understand false beliefs.

Infants predict expressers' cooperative behavior through facial expressions.

This study investigated infants' ability to use facial expressions to predict the expressers' subsequent cooperative behavior. To explore this problem, Experiment 1 tested 10- and 14-month-olds (N = 16, respectively) by using a violation-of-expectation procedure. In the experiment, all infants were first familiarized with two models, one with a happy facial expression and the other with an angry expression. They were also familiarized with an event in which a duck puppet tried to open a box but failed. During the test phase, infants in the helping condition saw two test scenes; one in which the happy model helped the duck open the box, and the other in which the angry model helped the duck. Infants in the hindering condition saw a test scene in which the happy model hindered the duck and the other test scene in which the angry model hindered the duck. The results demonstrated that both 10- and 14-month-olds looked longer at the angry model than at the happy model in the helping condition, whereas they looked at the happy model as long as the angry model in the hindering condition. Experiment 2 tested 6-month-olds (N = 16) with a slightly modified procedure and found the same tendency as shown by 10- and 14-month-olds. These results suggest that infants as early as at 6 months do not predict that a person with an angry expression will help others. However at the same time, they do not clearly understand the incongruence between happy expressions and hindering behavior. The results were discussed by referring to a negativity bias and human environment in which infants grow up.

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.

[Inferring the meaning of a novel adjective by Japanese preschoolers].

This study examined how Japanese preschoolers infer the meaning of a novel adjective and noun. The participants, 41 three-year-olds and 44 four-year-olds, were introduced to a novel adjective or a novel noun in association with a familiar object. They were then shown five test objects and asked to choose all the objects to which they could apply the novel word. The results indicated that although both three- and four-year-olds tried to extend adjectives using a different principle from nouns, only four-year-olds successfully extended a novel adjective based on the sameness of property. Three-year-olds seem to have trouble extracting a common property across objects especially when those objects belong to different basic-level categories.

Object similarity bootstraps young children to action-based verb extension.

Young children often fail to generalize a novel verb based on sameness of action since they have difficulty focusing on the relational similarity across events while at the same time ignoring the objects that are involved. Study 1, with Japanese-speaking 3- and 4-year-olds (N = 28 in each group), found that similarity of objects involved in action events plays a scaffolding role in children's extraction of relational similarity across events when they extend a verb. Study 2, with 4-year-olds (N = 47), further showed that repeated experience of action-based verb extension supported by object similarity leads children to be better able to extend a novel verb based on sameness of action, even without support from object similarity.

A developmental shift from similar to language-specific strategies in verb acquisition: a comparison of English, Spanish, and Japanese.

The world's languages draw on a common set of event components for their verb systems. Yet, these components are differentially distributed across languages. At what age do children begin to use language-specific patterns to narrow possible verb meanings? English-, Japanese-, and Spanish-speaking adults, toddlers, and preschoolers were shown videos of an animated star performing a novel manner along a novel path paired with a language-appropriate nonsense verb. They were then asked to extend that verb to either the same manner or the same path as in training. Across languages, toddlers (2- and 2.5-year-olds) revealed a significant preference for interpreting the verb as a path verb. In preschool (3- and 5-year-olds) and adulthood, the participants displayed language-specific patterns of verb construal. These findings illuminate the way in which verb construal comes to reflect the properties of the input language.

Novel noun and verb learning in Chinese-, English-, and Japanese-speaking children.

When can children speaking Japanese, English, or Chinese map and extend novel nouns and verbs? Across 6 studies, 3- and 5-year-old children in all 3 languages map and extend novel nouns more readily than novel verbs. This finding prevails even in languages like Chinese and Japanese that are assumed to be verb-friendly languages (e.g., T. Tardif, 1996). The results also suggest that the input language uniquely shapes verb learning such that English-speaking children require grammatical support to learn verbs, whereas Chinese children require pragmatic as well as grammatical support. This research bears on how universally shared cognitive factors and language-specific linguistic factors interact in lexical development.

[Understanding the symbolic values of Japanese onomatopoeia: comparison of Japanese and Chinese speakers].

Do non-native speakers of the Japanese language understand the symbolic values of Japanese onomatopoeia matching a voiced/unvoiced consonant with a big/small sound made by a big/small object? In three experiments, participants who were native speakers of Japanese, Japanese-learning Chinese, or Chinese without knowledge of the Japanese language were shown two pictures. One picture was of a small object making a small sound, such as a small vase being broken, and the other was of a big object making a big sound, such as a big vase being broken. Participants were presented with two novel onomatopoetic words with voicing contrasts, e.g.,/dachan/vs./tachan/, and were told that each word corresponded to one of the two pictures. They were then asked to match the words to the corresponding pictures. Chinese without knowledge of Japanese performed only at chance level, whereas Japanese and Japanese-learning Chinese successfully matched a voiced/unvoiced consonant with a big/small object respectively. The results suggest that the key to understanding the symbolic values of voicing contrasts in Japanese onomatopoeia is some basic knowledge that is intrinsic to the Japanese language.

Mapping novel nouns and verbs onto dynamic action events: are verb meanings easier to learn than noun meanings for Japanese children?

The present research examined how 3- and 5-year-old Japanese children map novel nouns and verbs onto dynamic action events and generalize them to new instances. Studies 1 to 3 demonstrated that although both 3- and 5-year-olds were able to map novel nouns onto novel objects, only 5-year-olds could generalize verbs solely on the basis of the sameness of the action. Study 4 showed that the difficulty young children experience in learning verbs lies mainly in mapping the appropriate element to a verb rather than in encoding and remembering an action itself. The results of this research are related to a long-debated issue of whether noun learning is privileged over verb learning.

Reorganizing the lexicon by learning a new word: Japanese children's interpretation of the meaning of a new word for a familiar artifact.

This research investigated how children interpret the meaning of a new word associated with a familiar artifact. The existing literature has shown that syntactic form-class information plays an important role in making this kind of inference. However, this information is not available to Japanese children, because Japanese language does not have a grammatical distinction between count nouns and mass nouns, proper nouns and common nouns, or singular and plural. In Study 1, 12 three-year-old monolingual Japanese children were tested to examine whether they interpreted a new noun associated with a familiar artifact to be a material name or a new label for the object. They interpreted the new word as a new category label for the object, rather than as a name for the material. How children related the new category to the old familiar one was then examined in Studies 2 and 3. The results of Study 2, in which 24 three-year-olds participated, showed that children could flexibly shift between two interpretations using shape information. When the named object had a typical shape for the familiar category, they mapped the new word to a subordinate category. In contrast, when the shape of the named object was atypical, they mapped the new word to a new category that was mutually exclusive to the familiar category by excluding the named object from the familiar category. In Study 3, 12 three-year-olds were tested to examine relative importance of shape and functional information in this inference process. The results of the three studies suggest that children flexibly recruit clues from multiple sources, but the cluesare weighed in hierarchical order so that they can determine the single most plausible solution in a given situation when different clues suggest different solutions.