Infant-Caregiver Vocal Contingency Changes Across Varying Interpersonal Space

Vocal contingency between caregivers and infants is a fundamental building block forsocio-communicative development. This paper investigates vocal contingency in homesettings and how it varies as a function of the physical distance between infants andtheir caregivers. We recorded 61 mother–infant dyads when infants were 5 to 14months old during daylong recording sessions, using wearable audio and proximitysensors. In total, 737 hours of indoor audio data were processed with machinelearning–based pipelines to extract and classify vocalisations automatically. When weconsidered all ages and proximities, we observed that mothers vocalised contingentlyto their infants, but that infants did not. Unexpectedly, above-chance contingency didnot increase with age for either partner. However, contingency varied with proximity ina quadratic fashion: it strengthened when dyads were closer, peaking at approximately0.4 m, and decreasing thereafter. This profile remained stable across ages.Importantly, above-chance contingency was also observed in infants (in addition tomothers) at proximities that fell between 0.3–0.5 m. The selective emergence of infantvocal contingency at these proximities suggests that face-to-face exchanges maypotentiate vocal contingency in infancy.