Identifying Direct and Indirect Influences on Vocabulary Development of Children from Low-Income Families from Infancy to Grade 5

We used structural equation models to explore how a constellation of factors affected vocabulary development trajectories of infants (N = 556; 49.6% male) from low-income families who comprised the control group of the Early Head Start Research Evaluation project. Predictors assessed at age 14 months accounted for 23.5%, 25.8%, and 30.6% of variance in receptive vocabulary (Peabody Picture Vocabulary Test) at 36 months, Pre-K, and Grade 5, respectively. Joint attention, assessed during free play (3-bags task), and infant cognitive ability (Bayley Mental Development Index) had stable direct associations with vocabulary knowledge. Negative mother-infant interaction co-varied with joint attention but had no direct effect on vocabulary knowledge at any age. Gestational age was indirectly associated with vocabulary knowledge via infant cognitive ability. Home environment, maternal education, maternal distress, and child gender had variable direct and/or indirect effects. Latent factors and models were partially invariant for subgroups of children of Black/African American and White/European American mothers. The findings indicate long-term impact of joint attention and related factors on vocabulary growth at least through Grade 5, highlighting the importance of designing interventions to support mothers and infants living in poverty.