Method: We used data from the Early Growth and Development Study, a longitudinal study of adoptive families (N=561). Effortful control (assessed with adoptive parent report on the Children’s Behavior Questionnaire at 4.5 and 6 years) and child cooperative play (assessed with adoptive parent report on the Pennsylvania Interactive Peer Play Scale at 4.5 and 6 years), were conceptualized as indexing cognitive and social domains of school readiness, respectively. Heritable influences were indexed with a birth parent agreeableness temperament factor measured with the Adult Temperament Questionnaire, Temperament and Character Inventory, and Harter Adult Self-Perception Profile. Child school achievement was assessed with the reading and math fluency scale from the Woodcock–Johnson Tests of Achievement at age 7.
Results: Birth parent agreeableness was directly associated with child effortful control (b = 0.10, p<.01) and cooperative peer play at 4.5 years (b = 0.11, p<.05). In addition to stability in child effortful control (b = 0.58, p<.01) and cooperative peer play (b=0.64, p<.01) from 4.5 to 6 years, child effortful control at 4.5 years elicited cooperative peer play at 6 years (b = 0.13, p<.01) and cooperative peer play at 4.5 years elicited child effortful control at 6 years (b = 0.16, p<.01). However, only child effortful control at age 6 was associated with subsequent reading (b = 0.23, p<.05) and math fluency (b = 0.20, p<.05). The direct effect of birth parent agreeableness on child effortful control and cooperative peer play indirectly conferred a protective effect on effortful control (b = 0.02, p<.01) and cooperatively peer play (b = 0.05, p<.01) at age 6. However, there was no indirect effect of birth parent agreeableness on reading and math fluency at age 7.
Discussion: These findings provide evidence of a heritable bidirectional relationship between early effortful control and cooperative peer play. Future research should take an integrative approach that examines the influence of heritable aspects of child characteristics on school readiness.