Bilingual Education and Cognitive Development in the Lower Primary Years: Evidence from Igbo-English Schools in Anambra State

The cognitive advantages associated with bilingual education have been extensively documented in European and North American research traditions, but the cognitive developmental outcomes of Igbo-English bilingual education in the lower primary years of Nigerian schooling have not been empirically investigated using robust cognitive assessment methodology. This dissertation investigates the relationship between bilingual education and cognitive development in lower primary school children in Anambra State, focusing on executive function, metalinguistic awareness, and academic concept formation as cognitive outcome dimensions. A longitudinal quasi-experimental design compared one hundred and twenty-six pupils in Igbo-English bilingual programme schools with a matched control group of ninety-eight pupils in English-medium schools across three assessment waves in Primary 1, Primary 2, and Primary 3. Cognitive assessment batteries adapted for the Anambra State context measured inhibitory control and cognitive flexibility as executive function components, phonological and morphological awareness as metalinguistic dimensions, and science and mathematics concept attainment as academic cognition indicators. Growth curve modelling of longitudinal data reveals significant bilingual programme advantages for cognitive flexibility and morphological awareness at all three assessment waves, with advantages on inhibitory control emerging from wave two. Bilingual programme pupils also show faster concept formation growth trajectories in mathematics but not science across the three waves. The dissertation engages with threshold theory, interdependence hypothesis, and recent multilingual cognition research to interpret findings. Original theoretical contributions address the transferability of cognitive advantage models to sub-Saharan African bilingual contexts. Keywords: bilingual education, cognitive development, lower primary, Igbo-English, Anambra State.