Periodic Reporting for period 1 - OptimisingIDS (Optimisation of the linguistic input in the first years of life)
Reporting period: 2018-09-01 to 2020-08-31
When parents interact with young infants, they spontaneously use a special type of speech known as infant-directed speech, also known as babytalk or parentese. Compared to adult-directed speech, infant-directed speech has a number of characteristic acoustic and linguistic components, which have been proposed to serve specific functions in young infants’ emotional and linguistic development. This fellowship focused on identifying the components that specifically serve a linguistic function; that is, the properties of infant-directed speech that assist infants in the challenging task of learning their native language. In addition, this was the first project to investigate these properties in infant-directed speech produced by bilingual parents in interactions with bilingual infants. Unlike their monolingual peers, bilingual infants face the additional challenge of differentiating their two native languages and tracking the information belonging to each language separately, so it is possible that the linguistic adaptations of infant-directed speech may yield additional benefits for this infant population.
This project pursued two main objectives: (1) To identify the individual acoustic components of infant-directed speech in relation to infants’ age and language ability, and (2) To experimentally isolate these individual components of infant-directed speech and measure the extent to which each component facilitates language processing in the first year of life. For this purpose, a combination of detailed acoustic analyses and experimental behavioral and neurophysiological tasks were used with four- to nine-month-old infants who were acquiring Spanish and Basque in monolingual and bilingual contexts.
This research has several practical implications. First, it enriches our understanding about bilingual language development. The majority of infants around the world acquire more than one language from birth, yet most current knowledge about language development is based on monolingual evidence. The results of this research inform caregivers and educators that with rich language exposure, bilingual infants can achieve dual-language proficiency that is on par with the one-language proficiency of their monolingual peers. Second, these results demonstrate that parents have direct access to one of the most effective child development tools - their own infant-directed speech. Access to rich linguistic input allows infants to develop language abilities in a rapid and effortless manner in their first years of life. This fellowship concentrated on identifying the components of infant-directed speech critical to enhance language development and provide monolingual and bilingual infants with the optimal type of linguistic input to achieve their maximum potential in the development of early language abilities.
This project pursued two main objectives: (1) To identify the individual acoustic components of infant-directed speech in relation to infants’ age and language ability, and (2) To experimentally isolate these individual components of infant-directed speech and measure the extent to which each component facilitates language processing in the first year of life. For this purpose, a combination of detailed acoustic analyses and experimental behavioral and neurophysiological tasks were used with four- to nine-month-old infants who were acquiring Spanish and Basque in monolingual and bilingual contexts.
This research has several practical implications. First, it enriches our understanding about bilingual language development. The majority of infants around the world acquire more than one language from birth, yet most current knowledge about language development is based on monolingual evidence. The results of this research inform caregivers and educators that with rich language exposure, bilingual infants can achieve dual-language proficiency that is on par with the one-language proficiency of their monolingual peers. Second, these results demonstrate that parents have direct access to one of the most effective child development tools - their own infant-directed speech. Access to rich linguistic input allows infants to develop language abilities in a rapid and effortless manner in their first years of life. This fellowship concentrated on identifying the components of infant-directed speech critical to enhance language development and provide monolingual and bilingual infants with the optimal type of linguistic input to achieve their maximum potential in the development of early language abilities.
This fellowship consisted of three experimental studies. Study 1 included 160 monolingual and bilingual five- and nine-month-old infants and their caregivers. Infants completed a speech perception task that assessed their ability to discriminate speech sounds that do and do not belong to the phonetic inventory of their native language(s). In addition, they took part in a naturalistic play session with their caregivers in which caregivers’ speech was recorded and subjected to detailed analyses to isolate the acoustic and linguistic components of their infant-directed speech. Studies 2 and 3 included 120 monolingual and bilingual eight- and four-month-old infants who completed age-appropriate language processing tasks (speech segmentation for eight-month-olds in Study 2 and neural tracking of speech for four-month-olds in Study 3). Infants were presented with acoustically manipulated infant-directed speech, in which the acoustic components predicted to facilitate language processing were either enhanced or suppressed.
First, results revealed that monolingual and bilingual caregivers exaggerate the acoustic properties of speech sounds when they address their infants compared to typical adult-directed speech. This adjustment has been proposed to enhance the clarity of infant-directed speech, and it is the first study to document it in speakers of Spanish and Basque. Critically, the degree to which parents exaggerated sounds in their speech was related to their infants’ speech perception abilities, so parents who spoke with greater clarity in interactions with their infants had infants with more mature speech perception abilities. Moreover, infant-directed speech with experimentally enhanced speech clarity elicited more successful language processing in bilingual infants in a challenging task that required them to differentiate their two languages and separately encode linguistic information belonging to each language. Therefore, these findings demonstrate that infant-directed speech possesses properties that foster language processing in young infants, especially in challenging communicative situations. Parents spontaneously produce these properties in interactions with their infants, and infants employ these properties of their language input according to the linguistic needs that are most relevant at each stage of the language acquisition process.
First, results revealed that monolingual and bilingual caregivers exaggerate the acoustic properties of speech sounds when they address their infants compared to typical adult-directed speech. This adjustment has been proposed to enhance the clarity of infant-directed speech, and it is the first study to document it in speakers of Spanish and Basque. Critically, the degree to which parents exaggerated sounds in their speech was related to their infants’ speech perception abilities, so parents who spoke with greater clarity in interactions with their infants had infants with more mature speech perception abilities. Moreover, infant-directed speech with experimentally enhanced speech clarity elicited more successful language processing in bilingual infants in a challenging task that required them to differentiate their two languages and separately encode linguistic information belonging to each language. Therefore, these findings demonstrate that infant-directed speech possesses properties that foster language processing in young infants, especially in challenging communicative situations. Parents spontaneously produce these properties in interactions with their infants, and infants employ these properties of their language input according to the linguistic needs that are most relevant at each stage of the language acquisition process.
These findings have a direct impact on the fields of early language acquisition and bilingualism. They contribute directly to the long-standing debate about the linguistic function of infant-directed speech by demonstrating that parents provide their infants with rich linguistic input that facilitates infants’ language acquisition, and infants in turn employ their input according to the linguistic needs that are most relevant at each stage of this process. Access to rich linguistic input allows infants to develop language abilities in a rapid and effortless manner in their first years of life. These language abilities are essential for efficient and effective acquisition of literacy skills and knowledge in all other academic areas when children start early formal education. However, not all children acquire these basic language skills to the same extent, giving some children a significant advantage even before they start school and leaving many others behind. Therefore, this work leads to significant practical implications. Understanding how the language environment can impact and enhance early language learning processes will inform not only the strategies for closing this gap in language ability, but the strategies to prevent it from emerging in the first place.