What do longitudinal studies from Chile and China tell us about early childhood and cognitive abilities?

The early years of childhood substantially shape cognitive development and long-term achievements. Synthesis of longitudinal studies is mainly based on different cohort study datasets; therefore, it lacks consistent cohort study protocols and measures of assessment. We selected two early-life cohort-based longitudinal studies conducted in Chile and China and reviewed 9 out of 75 research papers in which the two cohort study datasets were analyzed to assess the impact of attending formal school in early life. The selection of these 9 research pieces was based on stringent quality assessment criteria for reporting the analysis. None of the studies achieved the highest rating on the quality criteria. We synthesised findings from 9 studies, of which only 2 received a moderate quality rating, while 7 were rated low in quality. Therefore, claims on the role of factors remain inconclusive. The synthesis suggested that cognitive abilities in early childhood show positive associations with factors such as being a female child, having an older mother, high family income, and receiving cognitive stimulation at home. Conversely, negative factors such as low family income, being a left behind child, and maternal cigarette consumption are associated with adverse outcomes. Mixed factors such as early school attendance and maternal employment can have both positive and negative effects on child development, highlighting the intricate nature of the process.