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.

A robot is watching me!: Five-year-old children care about their reputation after interaction with a social robot.

Since robots are becoming involved in children's lives, it is urgent to determine how children perceive robots. The present study assessed whether Japanese 5-year-olds care about their reputation when interacting with a social robot. Children were given stickers and asked to divide them between themselves and an absent recipient. Results revealed that children (N = 112, 55 boys, 57 girls) strategically shared more stickers when being watched by a social interactive robot than by an attentional but non-interactive robot or a still robot. Additionally, children (N = 36, 18 boys, 18 girls) attributed higher psychological properties to social robots. This study is the first to show that 5-year-olds care about their reputations from social robots.

Do infants understand educational television content based on scientific findings?

Although attempts to create evidence-based television content for infants from birth to 2 years of age are notable, it has not been empirically verified to what extent infants understand such content. Our study evaluated whether Japanese 11- to 20-month-olds (N = 97; 52 boys and 45 girls) understand evidence-based television content using a looking-time method. When presented with content based on number themes, infants demonstrated an understanding of addition. When presented with content related to moral cognition, infants preferentially looked at a helper more than at a non-helper. Results reveal that infants understand educational television content based on scientific findings, demonstrating robustness and ecological validity. We discuss the possibility that broadcasting such content promotes infants' sensitivity to numbers and morals and provides learning opportunities through television.

Children's affiliation toward peers reflected in their picture drawings.

Previous studies have demonstrated that a picture-drawing task can be an indicator of the affiliation children have with their peers. When a child draws himself/herself along with a peer, the distance between them is assumed to represent the extent of the affiliation held by the child toward the peer: the shorter the distance is, the more affiliation the child has. However, some issues remain before the picture-drawing task is established as a way to measure children's affiliation, including the possibility that the instructions might bias the children's responses (Thomas & Gray, 1992), and inconsistency over where to measure in the children's drawings (e.g., Song et al., 2015). In this study, we focused on the above two issues and addressed whether the picture-drawing task can be used for measuring children's affiliation toward peers. We conducted our study in Japanese nursery schools with 3- to 6-year-old children (N = 676), who drew pictures of themselves and a classmate. Teachers rated how much the children had played with the drawn peer. We found that the more a child had an affiliative relationship with a peer, the shorter the distance between the drawn child and peer was when measuring the closest points and the center between the two drawn figures. Our research sheds light on the validity of the picture-drawing task for measuring children's affiliation.

Children's understanding of friendship formation caused by gossip.

Previous studies with adults argued that gossiping contributes to friendship formation. Although some evidence suggests that gossip is also ubiquitous in children's lives, whether children understand its effect has not been investigated. In this study, we examined how children aged 6-10 years understand the effect of gossip on friendship formation between two individuals. They heard six vignettes where a protagonist heard a piece of gossip about a target from a gossip spreader and answered whether the protagonist wanted to be friends with the spreader. In these vignettes, we manipulated the valence of gossip (positive/negative) and the shared mindset between the protagonist and the gossip spreader (having the same/opposite/no opinion about the gossip target). We found that the children thought that the protagonist wanted to form a friendship with the person who spread positive gossip, but the extent of the protagonist's desire to befriend the gossip spreader depended on their shared mindset. On the other hand, the children thought that the protagonist wanted to befriend the person who spread negative gossip when the protagonist had the same opinion about the target. These findings suggest that the children's inference of friendship formation caused by gossip depended on the valence of gossip and whether a shared mindset existed between the two individuals. This is the first evidence that reveals how children understand the social consequences of gossiping.

The Use of Pitch Accent in Word-Object Association by Monolingual Japanese Infants.

This study investigated the lexical use of Japanese pitch accent in Japanese-learning infants. A word-object association task revealed that 18-month-old infants succeeded in learning the associations between two nonsense objects paired with two nonsense words minimally distinguished by pitch pattern (Experiment 1). In contrast, 14-month-old infants failed (Experiment 2). Eighteen-month-old infants succeeded even for sounds that contained only the prosodic information (Experiment 3). However, a subsequent experiment revealed that 14-month-old infants succeeded in an easier single word-object task using pitch contrast (Experiment 4). These findings indicate that pitch pattern information is robustly available to 18-month-old Japanese monolingual infants in a minimal pair word-learning situation, but only partially accessible in the same context for 14-month-old infants.

Third-party punishment by preverbal infants.

Third-party punishment of antisocial others is unique to humans and seems to be universal across cultures. However, its emergence in ontogeny remains unknown. We developed a participatory cognitive paradigm using gaze-contingency techniques, in which infants can use their gaze to affect agents displayed on a monitor. In this paradigm, fixation on an agent triggers the event of a stone crushing the agent. Throughout five experiments (total N = 120), we show that eight-month-old infants punished antisocial others. Specifically, infants increased their selective looks at the aggressor after watching aggressive interactions. Additionally, three control experiments excluded alternative interpretations of their selective gaze, suggesting that punishment-related decision-making influenced looking behaviour. These findings indicate that a disposition for third-party punishment of antisocial others emerges in early infancy and emphasize the importance of third-party punishment for human cooperation. This behavioural tendency may be a human trait acquired over the course of evolution.

Early verb learning in 20-month-old Japanese-speaking children.

The present study investigated whether children's representations of morphosyntactic information are abstract enough to guide early verb learning. Using an infant-controlled habituation paradigm with a switch design, Japanese-speaking children aged 1 ; 8 were habituated to two different events in which an object was engaging in an action. Each event was paired with a novel word embedded in a single intransitive verb sentence frame. The results indicated that only 40% of the children were able to map a novel verb onto the action when the mapping task was complex. However, by simplifying the mapping task, 88% of the children succeeded in verb-action mapping. There were no differences in perceptual salience between the agent and action switches in the task. These results provide strong evidence that Japanese-speaking children aged 1 ; 8 are able to use an intransitive verb sentence frame to guide early verb learning unless the mapping task consumes too much of their cognitive resources.

An eye-tracking study of letter-sound correspondence in Japanese-speaking 2- to 3-year-old toddlers.

Although the acquisition of letter-sound correspondences is a critical step in reading development, how and when children develop such correspondence remains relatively unexplored. In this study, we focused on Japanese hiragana letters to examine the implicit letter-sound correspondence using an eye-tracking technique for 80 Japanese-speaking toddlers. The results showed that 32- to 48-month-olds (but not 24- to 32-month-olds) directed their gaze at the target letter. An additional experiment on a letter-reading task showed that 32- to 40-month-olds could barely read the presented hiragana letters. These findings suggest that toddlers have already begun to grasp implicit letter-sound correspondences well before actually acquiring the ability to read letters.

The impact of positive and negative testimony on children's attitudes toward others.

Children can identify who is benevolent or malevolent not only through first-hand experiences and observations but also from the testimony of others. In this study, we investigated whether 5- and 7-year-olds (N = 128) would form their attitudes toward others after hearing testimony about that person's past moral behavior and whether the valence of testimony would differently influence the children. In the positive condition, half of the participants gained information about three puppets: puppet A's prosocial behavior by their own first-hand observation, testimony about puppet B's past prosocial behavior, and testimony about puppet C's past neutral behavior. In the negative condition, the other half also learned information about the three puppets: puppet A's antisocial behavior by their own first-hand observation, testimony about puppet B's past antisocial behavior, and testimony about puppet C's past neutral behavior. Then they engaged in tasks that measured their behavioral attitudes toward the puppets and evaluated the goodness of each puppet to assess their attitudes at a cognitive level. Our results concluded that the children form their behavioral attitudes toward others based on testimony starting at the age of 7, and attitude formation at the cognitive level based on testimony is seen at age 5. Negative testimony, rather than positive testimony, influences the children's attitudes toward others. In addition, the 7-year-olds' use of testimony differs depending whether they are the allocators or the receivers of rewards. Our findings deepen understanding of how children rely on the verbal information around themselves when they navigate interactions with others.

Ostension affects infant learning more than attention.

A recent controversy in infants' social learning has revolved around whether ostensive cues have an effect beyond simply grabbing infants' attention: natural pedagogy theory vs. attention modulation theory. However, since previous research only focused on gaze-following behaviors, it has failed to determine whether attention-grabbing versus ostensive cues might affect infants' learning at different levels. To explore this possibility, we conducted a critical test with 9-month-old infants (N=140) in which gaze-following behavior was discriminated from referential learning about a target object (object processing and object preference). Here we report that although both attentional cues (shivering, a beep, and mouth-moving beep) and ostensive cues (infant-directed speech) affected infants' gaze-following, only ostensive cues facilitated their referential object learning. These findings provide new evidence that ostensive cues play a distinct role in infant learning, supporting natural pedagogy theory.

Relative quantity judgment by Asian elephants (Elephas maximus).

This study investigated whether Asian elephants can make relative quantity judgment (RQJ), a dichotomous judgment of unequal quantities ordered in magnitude. In Experiment 1, elephants were simultaneously shown two baskets with differing quantities of bait (up to 6 items). In Experiment 2, elephants were sequentially presented with baits, which could not be seen by elephants in their total quantities. The task of elephants was to choose the larger quantity in both experiments. Results showed that the elephants chose the larger quantity with significantly greater frequency. Interestingly, the elephants did not exhibit disparity or magnitude effects, in which performance declines with a smaller difference between quantities in a two-choice task, or the total quantity increases, respectively. These findings appear to be inconsistent with the previous reports of RQJ in other animals, suggesting that elephants may be using a different mechanism to compare and represent quantities than previously suggested for other species.

Sensitivity to register selection errors amongst 5- and 7-year-old children.

We are expected to behave appropriately to suit social situations. One form of behavioral control is the selection of a linguistic register that is appropriate to the listener. Register selection errors can sometimes be interpreted as rude behavior and result in having a bad influence on the relationship with the listener and the evaluation by other people. Previous studies have demonstrated that children begin to show sensitivity to registers from about 2 years of age, and that 5- to 6-year-old children understand the appropriate relationships between a listener and a register. However, it remains unclear whether and when children understand the influence made by register selection errors on listeners, and how children evaluate speakers when they make errors in register selection. Therefore, we investigated the above issues in Japanese children, who are required to use registers strictly. Also, we conducted a control study with Japanese-speaking adults to identify adults' evaluation of register selection errors. The results indicated that 7-year-old, but not 5-year-old children understood that the selection of an appropriate register gives listeners positive feelings. Moreover, 7-year-old children used register selection as an index of selective learning and social preference, although how they use others' register use skills for evaluating them was slightly different from adults. These results suggest that although children notice the social meanings behind the use of registers by the age of 7, a more extended period of development is required to master the social meaning of register selection. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Sensitivity to linguistic register in 20-month-olds: Understanding the register-listener relationship and its abstract rules.

Linguistic register reflects changes in speech that depend on the situation, especially the status of listeners and listener-speaker relationships. Following the sociolinguistic rules of register is essential in establishing and maintaining social interactions. Recent research suggests that children over 3 years of age can understand appropriate register-listener relationships as well as the fact that people change register depending on their listeners. However, given previous findings that infants under 2 years of age have already formed both social and speech categories, it may be possible that even younger children can also understand appropriate register-listener relationships. The present study used Infant-Directed Speech (IDS) and formal Adult-Directed Speech (ADS) to examine whether 20-month-old toddlers can understand register-listener relationships. In Experiment 1, we used a violation-of-expectation method to examine whether 20-month-olds understand the individual associations between linguistic registers and listeners. Results showed that the toddlers looked significantly longer at a scene in which the adult was talked to in IDS than when the infant was talked to in IDS. In contrast, there was no difference when the adult and the infant were talked to in formal ADS. In Experiments 2 and 3, we used a habituation switch paradigm to examine whether 20-month-olds understand the abstract rule that a change of register depends on listeners rather than on speakers. Results showed that the toddlers looked significantly longer at the scene where the register rule was violated. The present findings provide new evidence that even 20-month-olds already understand that people change their way of speaking based on listeners, although their understanding of individual register-listener relationships is immature.

Children passively allow other's rule violations in cooperative situations.

Recent studies in developmental psychology have revealed the developmental origins of cooperation. Although such studies regard cooperation as a pro-social behavior, studies on adults have found a negative aspect: cooperation sometimes promotes unethical behavior. Adults also exhibit altruistic cheating, even though their cheating might not actually benefit them. However, the development of negative aspects of cooperation remains unclear. Our study examined whether 7-year-old children engage in negative aspects of cooperation from two aspects using a peeking paradigm. Specifically, Experiment 1 examined children's negative aspects of cooperation from the perspective of collaboration and Experiment 2 examined altruistic behavior. Results of Experiment 1 revealed that children kept the cheating of a collaborative partner secret even though they did not actively cheat themselves. In Experiment 2, children also kept the partner's cheating secret even when violations did not provide any reward to themselves, if the predefined reward was high. In contrast, children did not keep the cheating secret if the predefined reward was low. Overall, our findings suggest that even 7-year-olds tend to act as if cooperating is more important than following rules that are compatible and exhibit negative aspects of cooperation.

Individual differences in object-processing explain the relationship between early gaze-following and later language development.

Gaze-following behaviors play an important role in language development. However, the way in which gaze-following contributes to language development remains unclear. By focusing on two abilities, namely following the gaze direction of others and processing a cued object, the present study investigated how these two influences work together to promote language development in a longitudinal approach on infants from 9 to 18months of age. The results demonstrated that infants who spent more time following the gaze direction toward an object were more efficient in processing the cued object at 9months and had larger vocabularies by 18months. Mediation analyses showed that the relationship between early gaze-following behavior and subsequent vocabulary size was explained by object-processing ability. Importantly, mere extended fixations on a target object without the initiation of another's gaze shift were not related to enhanced object-processing. Our findings suggest that following another's gaze shift toward the object has an impact on object-processing that could contribute to vocabulary development, elucidating a critical step in the path from early gaze-following ability to later language development.

Eye Contact Affects Object Representation in 9-Month-Old Infants.

Social cues in interaction with others enable infants to extract useful information from their environment. Although previous research has shown that infants process and retain different information about an object depending on the presence of social cues, the effect of eye contact as an isolated independent variable has not been investigated. The present study investigated how eye contact affects infants' object processing. Nine-month-olds engaged in two types of social interactions with an experimenter. When the experimenter showed an object without eye contact, the infants processed and remembered both the object's location and its identity. In contrast, when the experimenter showed the object while making eye contact with the infant, the infant preferentially processed object's identity but not its location. Such effects might assist infants to selectively attend to useful information. Our findings revealed that 9-month-olds' object representations are modulated in accordance with the context, thus elucidating the function of eye contact for infants' object representation.

Baby arithmetic: one object plus one tone.

Recent studies using a violation-of-expectation task suggest that preverbal infants are capable of recognizing basic arithmetical operations involving visual objects. There is still debate, however, over whether their performance is based on any expectation of the arithmetical operations, or on a general perceptual tendency to prefer visually familiar and complex displays. Here we provide new evidence that 5-month-old infants recognize basic arithmetic operations across sensory modalities. Using a violation-of-expectation task that eliminated the possibility of the familiarity and complexity preference, 5-month-old infants were presented alternatively with two types of arithmetical events: the expected, correct outcomes of operations (1 object+1 tone=2 objects and 1 object+2 tones=3 objects) and the unexpected, incorrect ones (1 object+2 tones=2 objects and 1 object+1 tone=3 objects). Results showed that subjects looked significantly longer at the unexpected events than at the expected events, suggesting that infants are able to recognize basic arithmetic operations across sensory modalities.

Audiovisual matching of lips and non-canonical sounds in 8-month-old infants.

Japanese 8-month-olds were tested to investigate the matching of particular lip movements to corresponding non-canonical sounds, namely a bilabial trill (BT) and a whistle (WL). The results showed that the infants succeeded in lip-voice matching for the bilabial trill, whereas they failed to do so for the whistle.

Evidence of means-end behavior in Asian elephants (Elephas maximus).

The present study explores to what extent Asian elephants show "means-end" behavior. We used captive Asian elephants (N = 2) to conduct four variations of the Piagetian "support" problem, which involves a goal object that is out of reach, but rests on a support within reach. In the first condition, elephants were simultaneously presented with two identical trays serving as the "support", with the bait on one tray and the other tray left empty. In the next two conditions, the bait was placed on one tray, while additional bait was placed beside the other tray. In the last condition, both trays contained bait, but one of the trays had a small gap which prevented the elephants from reaching the reward. Subjects were required to choose and pull either tray with their trunk and to obtain the bait (i.e. goal). Results showed that one elephant performed all of the support problems significantly above chance after several sessions, suggesting that the elephant was capable of understanding that pulling the tray was the "means" for achieving the "end" of obtaining the bait. This study showed that elephants show means-end behavior when subjected to a Piagetian "support" task, and indicates that such goal-directed behavior occurs in species other than primates.