Characterization of children's verbal input in a forager-farmer population using long-form audio recordings and diverse input definitions

Abstract

There is little systematically collected quantitative empirical data on how much linguistic input children in small-scale societies encounter, with some estimates suggesting low levels of directed speech. We report on an ecologically-valid analysis of speech experienced over the course of a day by young children (n = 24, 6-58 months old, 33% female) in a forager-horticulturalist population of lowland Bolivia. A permissive definition of input (i.e. including overlapping, background, and non-linguistic vocalizations) leads to a doubling of the estimate of target-child-directed input, and a quadrupling of the estimate for overall input compared to a restrictive definition (only near and clear speech), while who talked to and around a focal child is relatively stable across input definitions. We discuss implications of these results for theoretical and empirical research into language acquisition.

Vocal input and output among infants in a multilingual context: Evidence from long‐form recordings in Vanuatu

“…Three studies are most relevant because they provide input estimates for each speaker type and include all vocalizations (and not just those directed to the child): Casillas et al (2021) on 10 infants learning Yélî Dnye; Casillas et al (2020) on 10 children learning Tseltal; on 15 children learning Tsimane'; all three studies consider their participants to be largely monolingual. Estimates are much higher in this work than in Gilkerson's, and range from 16.9 min/h (Scaff et al, 2022) to 39 min/h (Casillas et al, 2020) total speech, collapsing across all speaker types. In all three populations, male adults provided little input, and instead, a majority of the input came from female adults, although a sizable proportion, increasing with age, came from other children (Bunce et al, 2020).…”

“…In contrast, the proportion of input from other children varies widely not only between Cougar and our data, but also across Tseltal, Tsimane', and Yélî data reported on in previous work. For instance, only 20% of Tseltal infants' input came from other children (Casillas et al., 2020); whereas other children contributed about as much to the input as female adults did among the Tsimane' (Scaff et al., 2022). Increases with age were only significant in two of these three studies (Casillas et al., 2021; Scaff et al., 2022), but in the remaining case, this may be due to limited power as only 10 infants could be included (Casillas et al., 2020).…”

“…For instance, only 20% of Tseltal infants' input came from other children (Casillas et al., 2020); whereas other children contributed about as much to the input as female adults did among the Tsimane' (Scaff et al., 2022). Increases with age were only significant in two of these three studies (Casillas et al., 2021; Scaff et al., 2022), but in the remaining case, this may be due to limited power as only 10 infants could be included (Casillas et al., 2020). Taking all of these results together, the picture is one of considerable diversity across populations that are otherwise similar in many respects, including the fact that young children have been described as integrating peer groups from a young age (as in many other societies; Hewlett & Cavalli‐Sforza, 1986; Lew‐Levy et al., 2020).…”

“…(2020) on 10 children learning Tseltal; and Scaff et al. (2022) on 15 children learning Tsimane'; all three studies consider their participants to be largely monolingual. Estimates are much higher in this work than in Gilkerson's, and range from 16.9 min/h (Scaff et al., 2022) to 39 min/h (Casillas et al., 2020) total speech, collapsing across all speaker types.…”

“…(2022) on 15 children learning Tsimane'; all three studies consider their participants to be largely monolingual. Estimates are much higher in this work than in Gilkerson's, and range from 16.9 min/h (Scaff et al., 2022) to 39 min/h (Casillas et al., 2020) total speech, collapsing across all speaker types. In all three populations, male adults provided little input, and instead, a majority of the input came from female adults, although a sizable proportion, increasing with age, came from other children (Bunce et al., 2020).…”