Read the summaries of research on developmental sequences by Vivian Cook, a leading UK second language researcher.

Cook identifies three important questions to ask about developmental sequences:

• which forms do second language learners use in which order?
• how does this acquisitional order compare with first language learners?
• how can the sequence be explained?

Read Cook's research synopses and try his exercises to learn about:

1. the morpheme studies (Burt & Dulay)
2. the processability model (or multidimensional model; Pienemann et al.)