The document summarizes research on the optimal starting age for second language acquisition. It discusses how age-related differences in SLA inform decisions about language education in Hong Kong. Specifically, it finds that while early starters may progress faster initially, older starters often perform better in the long term. The crucial comparison is long-term proficiency between age groups learning a language for the same duration. More evidence is needed to say whether early or late starters in Hong Kong maintain superiority over time.