Cross-language Transfer in Bilingual Poorer Readers: Effects of a Literacy Intervention on Word Reading

Approximately 40% of children worldwide learn to read in a language other than their home language or in two languages simultaneously. Evidence suggests that instruction in one language can enhance literacy outcomes in the other; however, the existence and longevity of these cross-language effects in poorer readers is unclear. This study used a cross-over randomised controlled trial design. Initially, 129 children (mean age = 111.44 months, SD = 12.23) participated in a 15-week Welsh literacy intervention, while 128 children (mean age = 110.62 months, SD = 12.34) served as a wait-list control group and did not receive the intervention during this period. After the first intervention phase, the wait-list control group then participated in the same 15-week Welsh literacy intervention. Welsh and English reading efficiency were assessed at three time points: baseline (t1; prior to intervention), posttest (t2; immediately after the initial intervention phase for the first group), and follow-up (t3; approximately 3-months after t2). We found that training poorer bilingual readers using a language-rich literacy intervention in Welsh improved word decoding skills in both Welsh and English. These effects were sustained in the longer term for the trained language, Welsh, but were short-lived for the untrained language, English. Our findings suggest that targeted intervention in one language enhances cognitive processes underlying literacy in both languages, and that bilingual students struggling with reading skills can make short-term literacy gains from a monolingual intervention that transfer to a language where there has not been explicit training.