How Do Individual-Difference Variables Affect Adolescent Learners’ L2 English Speaking Development? A Microgenetic Study

Researchers have found that learners’ second language development is influenced by internal and external individual differences but only few studies have adopted a longitudinal approach. In the present study, I aimed to investigate how several internal and external individual differences were interrelated and whether and how these variables predicted L2 English speaking development in adolescent learners. I conducted a dense longitudinal study with frequent measurements of L2 speaking skills. Learners in the first year of secondary school (11 to 13 years old, n = 48) did a weekly speaking task from September to May. At the start of the study, the participants also did multiple tasks, which measured various individual differences. Spearman correlations were calculated to shed light on the relationships between individual-difference variables, and generalized additive mixed models were used to model learning trajectories over time and to investigate the role of individual differences in this development. Results showed that learners’ speaking scores were predicted by time and prior L2 English receptive vocabulary knowledge, which was the main predictor of L2 speaking skills. Vocabulary knowledge furthermore significantly correlated with measures of out-of-school exposure and motivation. The results showed the key role of vocabulary in the early stages of L2 English learning.