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Infant-directed speech (IDS) is phonetically distinct from adult-directed speech (ADS): It is typically considered to have special prosody--like higher pitch and slower speaking rates--as well as unique speech sound properties, for example, more breathy, hyperarticulated, and/or variable consonant and vowel articulation. These phonetic features are widely observed in the IDS of caregivers from urbanized contexts who speak a handful of very well-researched languages. Yet studies with more diverse socio-cultural and linguistic samples show that this "typical" IDS prosody is not consistently observed across cultures. We extended cross-cultural work by examining IDS speech segment articulation, which--like prosody--is also thought to be a characteristic phonetic feature of IDS that might aid speech and language development. Here we asked whether IDS vowels have different articulatory features compared to ADS vowels in two distinct linguistic and socio-cultural contexts: urban English-speaking Canadian mothers, and rural Lenakel- and Southwest Tanna-speaking ni-Vanuatu mothers (n = 57, 20-46 years of age). Replicating prior work, Canadian mothers had "more" variable vowels in IDS compared to ADS, but also did not show clear register differences for breathiness or hyperarticulation. Vowels spoken by ni-Vanuatu mothers showed very distinct articulatory tendencies, using "less" variable (and "less" breathy) IDS vowels. Along with other work showing diversity in IDS phonetics across populations, this paper suggests that any understanding of how IDS might aid speech and language development are best examined through a culturally- and linguistically-specific lens.

Mirror self-recognition (MSR) is considered to be the benchmark of objective self-awareness--the ability to think about oneself. Cross-cultural research showed that there are systematic differences in toddlers' MSR abilities between 18 and 24 months. Understanding whether these differences result from systematic variation in early social experiences will help us understand the processes through which objective self-awareness develops. In this study, we examined 57 18- to 22-month-old toddlers (31 girls) and their mothers from two distinct sociocultural contexts: urban Canada (58% of the subsample were Canadian-born native English-speakers) and rural Vanuatu, a small-scale island society located in the South Pacific. We had two main goals: (a) to identify the social-interactional correlates of MSR ability in this cross-cultural sample, and (b) to examine whether differences in passing rates could be attributed to confounding factors. Consistent with previous cross-cultural research, ni-Vanuatu toddlers passed the MSR test at significantly lower rates (7%) compared to their Canadian counterparts (68%). Among a suite of social interactive variables, only mothers' imitation of their toddlers' behavior during a free play session predicted MSR in the entire sample and maternal imitation partially mediated the effects of culture on MSR. In addition, low passing rates among ni-Vanuatu toddlers could not be attributed to reasons unrelated to self-development (i.e., motivation to show mark-directed behavior, understanding mirror-correspondence, representational thinking). This suggests that differences in MSR passing rates reflect true differences in self-recognition, and that parental imitation may have an important role in shaping the construction of visual self-knowledge in toddlers.

Gaze is considered a crucial component of early communication between an infant and her caregiver. When communicatively addressed, infants respond aptly to others' gaze by following its direction. However, experience with face-to-face contact varies across cultures, begging the question whether infants' competencies in receiving others' communicative gaze signals are universal or culturally specific. We used eye-tracking to assess gaze-following responses of 5- to 7-month olds in Vanuatu, where face-to-face parent-infant interactions are less prevalent than in Western populations. We found that--just like Western 6-month-olds studied previously--5- to 7-month-olds living in Vanuatu followed gaze only, when communicatively addressed. That is, if presented gaze shifts were preceded by infant-directed speech, but not if they were preceded by adult-directed speech. These results are consistent with the notion that early infant gaze following is tied to infants' early emerging communicative competencies and rooted in universal mechanisms rather than being dependent on cultural specificities of early socialization.

It is known that infant‐directed speech (IDS) plays a key role in language development. Previous research, however, has also identified significant variability across societies in terms of how often IDS occurs. For example, some studies report very little IDS in non‐western, small‐scale societies – including children growing up in small‐scale societies in Tanna, Vanuatu. This is surprising given that IDS is widely assumed as a common feature of human caregiving based on research conducted in urbanised populations which are more well‐studied. Here, we propose that IDS is only one of a suite of important caregiving behaviours that are produced during interactions with infants, which may vary by culture, perhaps being replaced by other, non‐verbal infant‐directed behaviours (IDB). We will examine previously collected data consisting of 94 semi‐structured 10‐min video observations of caregivers and their 18–24 month‐old children in rural Tanna, Vanuatu and urban Vancouver, Canada to identify and compare the proportion of time caregivers spend engaging in IDS and IDB during these interactions, both within and between societies. We define IDS as caregiver speech or vocalisations during the interaction with the infant, and we define IDB as non‐verbal behaviours that are produced with the infant during the interaction. This study aims to take a step towards a more generalised understanding of language development in children, moving beyond the urban and western societies in which our understanding of development is currently based, and the predicted results will aid in recognising different developmental pathways within multi‐cultural communities. [ABSTRACT FROM AUTHOR]

When speaking to infants, adults typically alter the acoustic properties of their speech in a variety of ways compared with how they speak to other adults; for example, they use higher pitch, increased pitch range, more pitch variability, and slower speech rate. Research shows that these vocal changes happen similarly across industrialized populations, but no studies have carefully examined basic acoustic properties of infant-directed (ID) speech in traditional societies. Moreover, some scholars have suggested that ID speech is culturally specific and does not exist in some small-scale societies. We examined fundamental frequency (F[subscript 0]) production and speech rate in mothers speaking to both infants and adults in three cultures: Fijians, Kenyans, and North Americans. In all three cultures, speakers used higher F0 when speaking to infants relative to when speaking to other adults, and they also used significantly greater F0 variation and fewer syllables per second. Previous research has found that American mothers tend to use higher pitch than do mothers from other cultures, but when maternal education was controlled in the current study, we did not find a significant difference in average pitch across our three populations. This is the first research systematically comparing spontaneous ID and adult-directed speech prosody between Western and traditional societies, and it is consistent with a large body of evidence showing similar acoustic patterns in ID speech across industrialized populations.

Variation in attachment quality was assessed in 92 one- to three-year-olds' (49 female, 43 male) attachment to their father, within and across two small-scale, subsistence populations: the Tsimane of lowland Bolivia (n = 29 dyads) and Tannese of Vanuatu (n = 63 dyads). Overall, the Tsimane and Tannese populations show similarity in the patterning of child–father attachment relative to samples from industrialized societies, with 52% of Tsimane dyads and 62% of Tannese dyads showing secure attachment. However, the insecure-ambivalent attachment was more frequent among Tsimane and Tannese dyads relative to samples from industrialized societies, and attachment security was greater for sons than for daughters in Tanna. Of several attributes of fathers, only reports by mothers of how frequently fathers play with their children are associated with child–father secure attachment. Fathers who scored highly on this measure were more likely to have children with secure attachments. Studies of child–father attachment are rare outside of industrialized populations yet are critical to understanding the mechanisms underlying child–father relationships. [ABSTRACT FROM AUTHOR]

The authors examined similarities and differences in Canadian and ni‐Vanuatu caregivers' child‐directed speech to their toddlers (N = 35, Mage: 21 months, 20 girls). Speech samples were collected (2013–2016) during free play and analyzed with a focus on describing parents' references to their toddlers. Canadian caregivers referred significantly more to toddlers' tangible characteristics (relative risk, RR = 2.12) and internal states (RR = 2.31), whereas ni‐Vanuatu caregivers referred more to actions (RR = 2.04). When referring to internal states, Canadian mothers referred significantly more to mind‐minded states, whereas ni‐Vanuatu caregivers referred more to body‐minded states (RR = 7.98). These findings are interpreted as capturing meaningful differences in toddlers' opportunities to attend to themselves. Implications for self‐concept development are discussed. [ABSTRACT FROM AUTHOR]

Teaching likely evolved in humans to facilitate the faithful transmission of complex tasks. As the oldest evidenced hunting technology, spear hunting requires acquiring several complex physical and cognitive competencies. In this study, we used observational and interview data collected among BaYaka foragers (Republic of the Congo) to test the predictions that costlier teaching types would be observed at a greater frequency than less costly teaching in the domain of spear hunting and that teachers would calibrate their teaching to pupil skill level. To observe naturalistic teaching during spear hunting, we invited teacher–pupil groupings to spear hunt while wearing GoPro cameras. We analysed 68 h of footage totalling 519 teaching episodes. Most observed teaching events were costly. Direct instruction was the most frequently observed teaching type. Older pupils received less teaching and more opportunities to lead the spear hunt than their younger counterparts. Teachers did not appear to adjust their teaching to pupil experience, potentially because age was a more easily accessible heuristic for pupil skill than experience. Our study shows that costly teaching is frequently used to transmit complex tasks and that instruction may play a privileged role in the transmission of spear hunting knowledge. [ABSTRACT FROM AUTHOR]

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It is widely held that intuitive dualism—an implicit default mode of thought that takes minds to be separable from bodies and capable of independent existence—is a human universal. Among the findings taken to support universal intuitive dualism is a pattern of evidence in which "psychological" traits (knowledge, desires) are judged more likely to continue after death than bodily or "biological" traits (perceptual, physiological, and bodily states). Here, we present cross‐cultural evidence from six study populations, including non‐Western societies with diverse belief systems, that shows that while this pattern exists, the overall pattern of responses nonetheless does not support intuitive dualism in afterlife beliefs. Most responses of most participants across all cultures tested were not dualist. While our sample is in no way intended to capture the full range of human societies and afterlife beliefs, it captures a far broader range of cultures than in any prior study, and thus puts the case for afterlife beliefs as evidence for universal intuitive dualism to a strong test. Based on these findings, we suggest that while dualist thinking is a possible mode of thought enabled by evolved human psychology, such thinking does not constitute a default mode of thought. Rather, our data support what we will call intuitive materialism—the view that the underlying intuitive systems for reasoning about minds and death produce as a default judgment that mental states cease to exist with bodily death. [ABSTRACT FROM AUTHOR]

We examined infant activity level and attention in 45 eight‐month‐old infants (mean age 8.8, SD = 2.07) living in two diverse socio‐cultural contexts: rural island societies in the South Pacific and urban Western societies in North America. Infants and mothers were observed for 10 minutes in a face‐to‐face interaction and later coded for the frequency of infants' motor movements and gaze shifts. Results indicate that infants in urban North American societies produced more frequent motor movements and gaze shifts compared to infants in rural, island societies in Oceania. We interpret these discrepancies as reflecting differences in social experience, ecological niches as well as physiological experiences. These findings highlight the complex interplay of development and experience early in life. [ABSTRACT FROM AUTHOR]

When speaking to infants, mothers often alter their speech compared to how they speak to adults, but findings for fathers are mixed. This study examined interactions (N = 30) between fathers and infants (Mage  ± SD = 7.8 ± 4.3 months) in a small-scale society in Vanuatu and two urban societies in North America. Fundamental frequency (F0 ) and speech rate were measured in infant-directed and adult-directed speech. When speaking to infants, fathers in both groups increased their F0 range, yet only Vanuatu fathers increased their average F0 . Conversely, North American fathers slowed down their speech rate to infants, whereas Vanuatu fathers did not. Behavioral traits can vary across distant cultures while still potentially solving similar communicative problems. [ABSTRACT FROM AUTHOR]

Humans are unique in their propensity for helping. Not only do we help others in need by reacting to their requests, we also help proactively by assisting in the absence of a request. Proactive helping requires the actor to detect the need for help, recognize the intention of the other, and remedy the situation. Very little is known about the development of this social phenomenon beyond an urban, industrialized setting. We examined helping in nineteen two- to five-year old children in small-scale rural villages of Vanuatu. In the experimental condition, the intentions of the experimenter were made salient, whereas in the control condition they were ambiguous. Children helped more often in the experimental compared to the control condition, suggesting that the propensity to monitor others’ goals and act accordingly can be detected in different cultural contexts. [ABSTRACT FROM AUTHOR]

Humans are unique in their propensity to intentionally instruct and subsequently learn a wide range of information from others. We investigated when and how young children become socially resourceful in using others’ expertise, and whether the early propensity to request for help varies across diverse societies. We tested and compared 44 two- to four-year-old children growing up in urban United States and Japan, and rural Canada. Children were faced with two experimenters who demonstrated different abilities (successful vs. unsuccessful) in a toy retrieving task. We measured children’s propensity to request for help and the relative selectivity of requests to one experimenter over another. Results show significant cross-cultural differences. U.S. children’s request behavior differed significantly from the other two societies on three of the four measures. Specifically, U.S. children requested more overall, whereas Japanese children ceased manipulation (“give up”), and Canadian children continued to try on their own. Only the U.S. children show clear selective requests to the successful experimenter. On the last measure (gaze behavior), the U.S. and Canadian children look more to the successful model during the test phase than the unsuccessful model. These findings have implications for social learning research as well as the generalizability of developmental science. [ABSTRACT FROM AUTHOR]

The range of symbols that children treat as object names narrows over the course of development as children accrue more experience with and exposure to language. By two years of age, children no longer treat gestures as object labels. Here we investigate the source of this new-found failure and ask whether it stems primarily from a failure to form associations between gestures and their referents, as opposed to a failure to interpret these associations as referential. To explore these possibilities, we tested word versus gesture learning in a paradigm consisting of both a preferential looking task (designed to detect implicit associations) and a forced-choice task (designed to index explicit symbol-to-referent mapping). Our findings reveal that unlike two-year-olds in the word condition, two-year-olds in the gesture condition failed to demonstrate associations between gestures and objects in either task, suggesting that they did not form associative links between gestures and their intended referent. Importantly, those who did exhibit associations during preferential looking were also more likely to demonstrate successful learning of gestures in the forced-choice task. In contrast, 18-month-olds readily formed associations between gestures and objects. We conclude that the decline in receptivity to gestural labels during the second year is due to a failure to form reliable associations between gestures and their referents. [ABSTRACT FROM AUTHOR]

Abstract: Self-recognition by 86 children (14–52months) was assessed using the mirror mark test in two different social contexts. In the classic mirror task condition, only the child was marked prior to mirror exposure (Classic condition). In the social norm condition, the child, experimenter, and accompanying parent were marked prior to the child’s mirror exposure (Norm condition). Results indicate that in both conditions children pass the test in comparable proportion, with the same increase as a function of age. However, in the Norm condition, children displayed significantly more hesitation while removing the mark, often touching it without removing it or, if so, promptly putting the mark back onto their forehead. In the Classic condition, only one child showed such hesitation. These results suggest that from the outset, mirror self-recognition can refer to social awareness. This link is interpreted as the trademark of human self-consciousness, a deeply rooted “looking glass” self-awareness. [Copyright &y& Elsevier]

This research investigates 3- and 5-year-olds' relative fairness in distributing small collections of even or odd numbers of more or less desirable candies, either with an adult experimenter or between two dolls. The authors compare more than 200 children from around the world, growing up in seven highly contrasted cultural and economic contexts, from rich and poor urban areas, to small-scale traditional and rural communities. Across cultures, young children tend to optimize their own gain, not showing many signs of self-sacrifice or generosity. Already by 3 years of age, self-optimizing in distributive justice is based on perspective taking and rudiments of mind reading. By 5 years, overall, children tend to show more fairness in sharing. What varies across cultures is the magnitude of young children's self-interest. More fairness (less self-interest) in distributive justice is evident by children growing up in small-scale urban and traditional societies thought to promote more collective values. [ABSTRACT FROM AUTHOR]