Infants' use of the index finger for social and non-social purposes during the first two years of life: A cross-cultural study.

The emergence of the pointing gesture is a major developmental milestone in human infancy. Pointing fosters preverbal communication and is key for language and theory of mind development. Little is known about its ontogenetic origins and whether its pathway is similar across different cultures. The goal of this study was to examine the theoretical proposal that social pointing is preceded by a non-social use of the index finger and later becomes a social-communicative gesture. Moreover, the study investigated to which extent the emergence of social pointing differs cross-culturally. We assessed non-social index-finger use and social pointing in 647 infants aged 3- to 24 months from 4 different countries (China, Germany, Japan, and Türkiye). Non-social index-finger use and social pointing increased with infants' age, such that social pointing became more dominant than non-social index-finger use with age. Whereas social pointing was reported across countries, its reported frequency differed between cultures with significantly greater social pointing frequency in infants from Türkiye, China, and Germany compared to Japanese infants. Our study supports theoretical proposals of the dominance of non-social index-finger use during early infancy with social pointing becoming more prominent as infants get older. These findings contribute to our understanding of infants' use of their index finger for social and non-social purposes during the first two years of life.

Associations of breastfeeding duration and cognitive development from childhood to middle adolescence.

AIM: To assess the dose-response association between the duration of any breastfeeding and cognitive skills in children from 5 to 15 years of age. METHODS: The data from the longitudinal cohort study Growing up in Australia: The Longitudinal Study of Australian Children (children born in 1999-2000 and 2003-2004) were accessed. Language skills were assessed via Peabody Picture Vocabulary Test at 5, 7 and 9 years of age (N = 8643), and non-verbal intelligence was assessed via Matrix Reasoning subtest from Wechsler Intelligence Scale at 7, 9 and 11 years of age (N = 8560) and executive functions were examined via Cogstate Cognitive Testing battery in 15 years old (N = 6213). Breastfeeding was assessed via maternal questionnaires, partly prospective. RESULTS: A longer duration of breastfeeding was significantly associated with greater language skills from 5 to 9 (0.05 [95% CI, 0.03-0.08], p < 0.0001) and greater non-verbal intelligence from 7 to 11 years of age (0.02 [95% CI, 0.01-0.04], p < 0.001). No significant relation was found between the breastfeeding duration and executive functions in 15 years old. CONCLUSION: These results support a dose-response relationship between breastfeeding duration and language skills and non-verbal intelligence during childhood and early adolescence.

The effect of older sibling, postnatal maternal stress, and household factors on language development in two- to four-year-old children.

Previous literature has shown that family structure affects language development. Here, factors relating to older siblings (their presence in the house, sex, and age gap), mothers (maternal stress), and household size and residential crowding were assessed to systematically examine the different roles of these factors. Data from mother-child dyads in a Singaporean birth cohort, (677-855 dyads; 52% males; 58% to 61% Chinese, 20% to 24% Malay, 17% to 19% Indian) collected when children were 24, 48, and 54 months old, were analyzed. There was a negative effect of having an older sibling, moderated by the siblings' age gap, but not by the older sibling's sex, nor household size or residential crowding. Maternal stress affected language outcomes in some analyses but not others. Implications for understanding the possible effects of family structure on language development are discussed. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Language development in infants with hearing loss: Benefits of infant-directed speech.

The majority of infants with permanent congenital hearing loss fall significantly behind their normal hearing peers in the development of receptive and expressive oral communication skills. Independent of any prosthetic intervention ("hardware") for infants with hearing loss, the social and linguistic environment ("software") can still be optimal or sub-optimal and so can exert significant positive or negative effects on speech and language acquisition, with far-reaching beneficial or adverse effects, respectively. This review focusses on the nature of the social and linguistic environment of infants with hearing loss, in particular others' speech to infants. The nature of this "infant-directed speech" and its effects on language development has been studied extensively in hearing infants but far less comprehensively in infants with hearing loss. Here, literature on the nature of infant-directed speech and its impact on the speech perception and language acquisition in infants with hearing loss is reviewed. The review brings together evidence on the little-studied effects of infant-directed speech on speech and language development in infants with hearing loss, and provides suggestions, over and above early screening and external treatment, for a natural intervention at the level of the carer-infant microcosm that may well optimize the early linguistic experiences and mitigate later adverse effects for infants born with hearing loss.

Acoustic features of infant-directed speech to infants with hearing loss.

This study investigated the effects of hearing loss and hearing experience on the acoustic features of infant-directed speech (IDS) to infants with hearing loss (HL) compared to controls with normal hearing (NH) matched by either chronological or hearing age (experiment 1) and across development in infants with hearing loss as well as the relation between IDS features and infants' developing lexical abilities (experiment 2). Both experiments included detailed acoustic analyses of mothers' productions of the three corner vowels /a, i, u/ and utterance-level pitch in IDS and in adult-directed speech. Experiment 1 demonstrated that IDS to infants with HL was acoustically more variable than IDS to hearing-age matched infants with NH. Experiment 2 yielded no changes in IDS features over development; however, the results did show a positive relationship between formant distances in mothers' speech and infants' concurrent receptive vocabulary size, as well as between vowel hyperarticulation and infants' expressive vocabulary. These findings suggest that despite infants' HL and thus diminished access to speech input, infants with HL are exposed to IDS with generally similar acoustic qualities as are infants with NH. However, some differences persist, indicating that infants with HL might receive less intelligible speech.