Overhearing conversations helps Tseltal Maya infants learn language effectively

A study published in the journal PNAS highlights the impact of overhearing-based learning on language development in infants who are rarely spoken to directly.

Tseltal mother carrying a nine-month-old infant. Study: Infants who are rarely spoken to nevertheless understand many words

Background

A wide-range of studies investigating language development in children have primarily considered the speech that parents or caregivers direct to children as the primary driver of language development. These studies have mostly been conducted on children raised in Western, middle-class, child-centered households.  

The primary highlight of these studies is that there may be a single, optimal pathway to language. This pathway involves frequent adult speech to children even before they learn to give meaningful replies. This is called child-directed language.

This particular theory of language development suggests that increasing the quantity and quality of child-directed language can increase language processing efficiency, vocabulary growth, optimal brain development, and subsequent educational attainment in children.

Some studies have argued this theory by reporting that language development occurs similarly across environmental contexts despite significant variation in child-directed language customs at the global scale.

This raises the possibility that children can learn from other language sources in their environment, especially the language they overhear from surrounding people.

In this study, scientists have investigated how other-directed language (overhearing) can facilitate language development in infants from an indigenous community in Southern Mexico who are rarely spoken to directly.

Study design

The study involved a Tseltal Maya society in Tenejapa, Chiapas, Mexico, where infants experience the world from a sling on their mothers’ backs.

Infants from this community are rarely addressed directly by caregivers or parents during the initial years of life. However, they have the opportunity to overhear a great deal of other-directed language by virtue of being carried on their mothers’ backs. They are exposed to direct speech only after they start walking and get a chance to interact with people around them.

The study employed a well-established “language-guided-looking” task to assess infants’ language knowledge. The task captures early word knowledge by measuring infants’ gaze between paired visual stimuli when prompted with one of their names.

Important observations

The study found that Tseltal infants exhibit implicit knowledge of common Tseltal nouns, which is similar to their US peers’ development of knowledge of common English nouns through child-directed language. This finding indicates that Tseltal infants are equivalent to US infants in terms of language development despite infrequent exposure to child-directed language.

Furthermore, the study found that Tseltal infants exhibit knowledge of Tseltal honorific greeting terms that are exclusively exchanged between adult members of the community. This finding indicates that Tseltal infants could learn these words only through overhearing.

Overall, these findings indicate that infants can learn from the other-directed language in their respective environments and that overhearing-based learning can be a crucial component of language development in some infants.

Study significance

The study provides a new perspective that children are able to successfully learn their native languages across variable environments partly because of their flexibility toward learning processes.

Language directed at children is not their only learning source. The language they overhear from their surrounding environments can also facilitate their language development, highlighting that children can play an active role in it.

This study contrasts with previous studies that identify child-directed language as the sole source of learning for language development in children. This might be because these studies have mostly involved children who are frequently exposed to child-directed language, whereas children included in the current study are rarely spoken to directly as they are almost always carried on their mothers’ backs.  

These findings provide a new path for future studies to investigate whether children from different environmental backgrounds are equally able to learn from child-directed and other-directed language or develop and adapt their learning strategies in response to their environments.  

As advised by the scientists, future studies could focus on measuring the composition of child-directed and other-directed language in their respective environments and evaluating the impact of this measure on children’s ability to learn from these two different language sources.

Future studies could also analyze and compare different types of other-directed language to determine which type is more conducive to learning than others.

The current study findings might be relevant for interventions encouraging caregivers to speak more to their young infants, particularly in contexts wherein this practice is not the cultural norm.