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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.

The intensifying pace of research based on cross-cultural studies in the social sciences necessitates a discussion of the unique challenges of multi-sited research. Given an increasing demand for social scientists to expand their data collection beyond WEIRD (Western, educated, industrialized, rich and democratic) populations, there is an urgent need for transdisciplinary conversations on the logistical, scientific and ethical considerations inherent to this type of scholarship. As a group of social scientists engaged in cross-cultural research in psychology and anthropology, we hope to guide prospective cross-cultural researchers through some of the complex scientific and ethical challenges involved in such work: (a) study site selection, (b) community involvement and (c) culturally appropriate research methods. We aim to shed light on some of the difficult ethical quandaries of this type of research. Our recommendation emphasizes a community-centred approach, in which the desires of the community regarding research approach and methodology, community involvement, results communication and distribution, and data sharing are held in the highest regard by the researchers. We argue that such considerations are central to scientific rigour and the foundation of the study of human behaviour.

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.

It has been hypothesized that sleep in the industrialized world is in chronic deficit, due in part to evening light exposure, which delays sleep onset and truncates sleep depending on morning work or school schedules. If so, societies without electricity may sleep longer. However, recent studies of hunter-gatherers and pastoralists living traditional lifestyles without electricity report short sleep compared to industrialized population norms. To further explore the impact of lifestyles and electrification on sleep, we measured sleep by actigraphy in indigenous Melanesians on Tanna Island, Vanuatu, who live traditional subsistence horticultural lifestyles, in villages either with or without access to electricity. Sleep duration was long and efficiency low in both groups, compared to averages from actigraphy studies of industrialized populations. In villages with electricity, light exposure after sunset was increased, sleep onset was delayed, and nocturnal sleep duration was reduced. These effects were driven primarily by breastfeeding mothers living with electric lighting. Relatively long sleep on Tanna may reflect advantages of an environment in which food access is reliable, climate benign, and predators and significant social conflict absent. Despite exposure to outdoor light throughout the day, an effect of artificial evening light was nonetheless detectable on sleep timing and duration.

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.

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.

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 (F0) 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. © 2014 Copyright Taylor & Francis Group, LLC.

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]

The psychological capacity to recognize that others may hold and act on false beliefs has been proposed to reflect an evolved, species-typical adaptation for social reasoning in humans; however, controversy surrounds the developmental timing and universality of this trait. Cross-cultural studies using elicited-response tasks indicate that the age at which children begin to understand false beliefs ranges from 4 to 7 years across societies, whereas studies using spontaneous-response tasks with Western children indicate that false-belief understanding emerges much earlier, consistent with the hypothesis that false-belief understanding is a psychological adaptation that is universally present in early childhood. To evaluate this hypothesis, we used three spontaneous-response tasks that have revealed early false-belief understanding in the West to test young children in three traditional, non-Western societies: Salar (China), Shuar/Colono (Ecuador) and Yasawan (Fiji). Results were comparable with those from the West, supporting the hypothesis that false-belief understanding reflects an adaptation that is universally present early in development.

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]

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. Keywords: sharing; culture; development; fairness; naive psychology

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]