Contingent turn-taking between parents and infants is positively correlated with child language outcome (Tamis-LeMonda, Bornstein & Baumwell, 2001; Marklund, Marklund, Lacerda & Schwarz, 2015). Many studies focus exclusively on mothers (e.g., Sung, Fausto-Sterling, Garcia Coll & Seifer, 2013). However, infants in Western countries acquire language with input both from mothers and fathers in varying degree, depending on how the family chooses to organize their parental leave. Sweden is an ideal country to study both mothers and fathers as caregivers for infants.

Parental contingency is often reported as response frequency within a time window after infant vocalizations (e.g., Johnson, Caskey, Rand, Tucker & Vohr, 2014). In this study, turn-taking contingency is measured by the duration of parent-child and child-parent switching pauses around infant vocalization with potential communicative intent. Fourteen (7 girls) infants and their primary and secondary caregivers were recorded in the family home when the infant was six months (M = 5 months 29 days, range: 5 months 3 days – 6 months 16 days). The audio recordings were collected two different days and lasted approximately ten minutes each. One of the days was a typical weekday on which the primary caregiver – in all cases the mother – was at home with the infant. The other day was a typical weekend day on which also the secondary caregiver – in all cases the father – was at home and spent time with the infant. On each of these days, a daylong LENA recording was also made to estimate the amount of exposure to female and male speech input on a typical day. Using Wavesurfer 1.8.5 (Sjölander & Beskow, 2010), on- and offset of all infant vocalizations were tagged as well as on- and offset for the surrounding switching pauses. If parent utterance and infant vocalization overlapped, switching pause duration received a negative value.

Two repeated measures ANOVAs were used to determine the effects of caregiver type (primary/secondary) and infant sex (girl/boy) on pause duration in infant-parent and parent-infant switching pauses. A main effect was found for caregiver type in infant-parent switching pauses (F(12,1) = 5.214; p = .041), as primary caregivers responded on average about 500 ms faster to infant vocalizations than secondary caregivers, with no effect of or interaction with infant sex. In parent-infant switching pauses, the main effect for caregiver type was almost significant (F(12,1) = 4.574; p = .054), with no effect of or interaction with infant sex. It is therefore fair to say that turn-taking between primary caregivers and 6-month-olds is more contingent than turn-taking between secondary caregivers and 6-month-olds.

Four linear regressions were then used to predict parent-infant and infant-parent switching pause duration from the average duration of female speech exposure and the average duration of male speech exposure across the two days, with the assumption that female speech duration equals speech input from the primary caregiver and male speech duration the secondary caregiver. None of the regression analyses turned out to be significant. However, it is likely that the greater contingency between primary caregivers and the infant is a function of greater turn-taking experience, that is, conversational turns rather than mere exposure to speech. Therefore, we will look next at the number of conversational turns for each caregiver separately and investigate whether they predict parental response contingency.

The present study shows that vocal turn-taking is more contingent between infants and primary caregivers than with secondary caregivers. Primary caregivers respond significantly faster to infant vocalizations than secondary caregivers and in turn, infants have a tendency to respond faster to primary caregivers. It is likely that this relationship is mediated by turn-taking experience, although this could not be shown with regression analyses using LENA estimates of total duration of speech exposure to primary and secondary caregiver.