The interplay of dopaminergic genotype and parent–child relationship in relation to intra‐individual response time variability in preschoolers: A replication study

Intra-individual response time variability (IIRTV) during cognitive performance is increasingly recognized as an important indicator of attentional control (AC) and related brain region function. However, what determinants contribute to preschoolers' IIRTV received little attention. The present study explored the interaction of dopaminergic polygenic composite score (DPCS) and the parent-child relationship in relation to preschoolers' IIRTV. In the initial sample, 452 preschoolers (M age = 5.17, SD = 0.92) participated in the study. The modified Flanker task was used to evaluate children's IIRTV and their parents were requested to complete the Parent-Child Relationship Scale to assess the parent-child relationship (closeness/conflict). DNA data were extracted from children's saliva samples, and a DPCS was created by the number of COMT, DAT1, and DRD2 alleles associated with lower dopamine levels. Results showed that DPCS significantly interacted with the parent-child closeness to impact preschoolers' IIRTV. Specifically, preschoolers with higher DPCS exhibited lower IIRTV under higher levels of the parent-child closeness, and greater IIRTV under lower levels of the parent-child closeness compared to those with lower DPCS, which supported the differential susceptibility theory (DST). A direct replication attempt with 280 preschoolers (M age = 4.80, SD = 0.86) was conducted to investigate whether the results were in accordance with our exploratory outcomes. The interactive effect of DPCS and the parent-child closeness on IIRTV was confirmed. Additionally, the significant interactive effect of DPCS and the parent-child conflict on IIRTV was found in the replication study. The findings indicate that preschoolers' IIRTV, as an indicator of AC and related brain region function, is influenced by the interactions of dopaminergic genotypes and the parent-child relationship. RESEARCH HIGHLIGHTS: We investigated the Gene × Environment mechanism to underline the intra-individual response time variability as an indicator of attentional control (AC) in Chinese preschoolers. Dopaminergic polygenic composite score (COMT, DAT1, and DRD2) interacted with the parent-child relationship to predict preschoolers' intra-individual reaction time variability. A direct replication attempt has been conducted, and the results were in accordance with our exploratory outcomes, which increased the credibility of the present findings. The findings highlight the importance of considering precursors, including polygenic and environmental factors, which contribute to the development of early cognitive performance such as AC.