Chapter 3. The role of executive function in the perception of L2 speech sounds in young balanced and unbalanced dual language learners
This fMRI study investigated neural activity evoked by L2 speech syllables in brain regions associated with executive function typically recruited by bilinguals in cognitive control tasks. The main areas examined were the bilateral anterior cingulate cortex, bilateral supplementary motor area, bilateral inferior frontal gyrus, and bilateral middle frontal gyrus. Based on the degree of discrepancy between L1 and L2 proficiency scores, twenty-nine children classified as balanced (smaller discrepancy) or unbalanced (larger discrepancy) dual language learners were matched for age, socioeducational background, years of education in L2, and L2 age of acquisition. Children passively listened to L2 syllables while a muted film was presented. The results showed that unbalanced learners had increased activity in multiple frontal regions bilaterally relative to balanced learners. Balanced learners showed increased activity in a region of the right temporal lobe. The results suggest that unbalanced learners who have more difficulty learning the second language engage regions of executive function to support the perception of L2 speech sounds.