When the goal is basic communicative ability for all students in a school setting, and when it is assumed that the child's native language will remain the primary language, it may be more efficient to begin second language teaching later. In research on school learners receiving a few hours of instruction per week, learners who start later (for example, at age 10,11, or 12) catch up very quickly with those who began earlier. Any school program should be based on realistic estimates of how long it takes to learn a second language. One or two hours a week - even for seven or eight years - will not produce very advanced second language speakers.
The learner's age is one of the characteristics which determine the way in which an individual approaches second language learning. But the opportunities for learning (both inside and outside the classroom), the motivation to learn, and individual differences in aptitude for language learning are also important determining factors in both rate of learning and eventual success in learning.

Summary
In this chapter, we have looked at the ways in which intelligence, aptitude, personality and motivational characteristics, learning styles, and age have been found to influence second language learning. We have learned that the study of individual learner variables is not easy and that the results of research are not entirely satisfactory. This is partly because of the lack of clear definitions and methods for measuring the individual characteristics. It is also due to the fact that these learner characteristics are not independent of one another: learner variables interact in complex ways. So far, researchers know very little about the nature of these complex interactions. Furthermore, in a classroom, a sensitive teacher, who takes learners' individual personalities and learning styles into account, can create a learning environment in which virtually all learners can be successful in learning a second language. Therefore, it remains difficult to make precise predictions about how a particular individual's characteristics influence his or her success as a language learner.

Sources and suggestions for further reading
General discussion of individual differences
Skehan, P. 1989. Individual Differences in Second Language Learning. London: Edward Arnold.