Relationship Between Joint Attention and Language in Multiparous and Uniparous Households

Through verbal and nonverbal dyadic engagement with caregivers, infants acquire two critical capacities for social engagement: joint attention and language. Children initiate joint attention (IJA) when they use eye contact and pointing (IJA bids) to direct the attention of a social partner to objects of common interest, which then helps children acquire object labels from their social partners. The present study was designed to examine differences in the effect of the number of children in the household (also known as “parity”) on the relationship between IJA and language development. We reasoned that infants who are only children (i.e., in uniparous homes), relative to infants who have one or more siblings (i.e., in multiparous homes), would have more opportunity to engage in IJA, and would, therefore, acquire a larger number of object labels. We tested the hypotheses that: 1) there would be a positive correlation between the number of IJA bids and language overall, and 2) parity would moderate the IJA-language relationship such that in uniparous households, the aforementioned correlation would be stronger than in multiparous homes. For this study, 73 primarily white, middle-class infants ranging from 12 to 20 months of age (30 uniparous, 40 multiparous, 3 missing) visited the lab. Using the Picture Book Task of the Early Social Communication Scales, IJA behaviors were coded when children made eye contact with the experimenter (lower IJA) or pointed to pictures in the book (higher IJA) without elicitation. Productive and receptive vocabulary was measured through parental report using the MacArthur-Bates Communicative Development Inventory. Preliminary analyses showed that older children had larger productive [r(30) = .50, p = .000] but not receptive vocabularies relative to younger children. Also, we were surprised to find that the ages of the infants in our investigation were not associated with the number of siblings in their homes since older infants would have been more likely to have younger siblings. In terms of our hypotheses, it was found that IJA was not associated with either language measure. To test for a moderation effect, we conducted a moderated regression analysis in which each language measure was regressed on IJA, the number of siblings in the home, and the interaction term for these two variables. The interaction term was statistically significant, indicating a moderation effect [B = -8.09, SD = 4.00, t = -2.02, p = .047]. However, this association disappeared after controlling for child age. Overall, our hypotheses were not supported. Although it is possible that parity has no moderating effect of on the IJA-language relationship, our sample size did not provide for large amounts of statistical power to make such a strong claim in this direction. Still, these null findings may provide positive reassurance for families with multiple children that their younger children are not at an IJA/language acquisition disadvantage