In Chapter 1, it was pointed out that all normal children, given a normal upbringing, are successful in the acquisition of their first language. This contrasts with our experience of second language learners, who vary greatly in their abilities to acquire their second language.
Many of us believe that learners have certain characteristics which lead to more or less successful language learning. Such beliefs are usually based on anecdotal evidence, that is, on individual people we have known. For example, many teachers are convinced that extroverted learners who interact without inhibition in their second language and find many opportunities to practise language skills will be the most successful learners. In addition to personality characteristics, other factors generally considered to be relevant to language learning are intelligence, aptitude, motivation, and attitudes. Another important factor, as our previous discussion of the critical period hypothesis for first language acquisition has suggested, is the age at which learning begins.
In this chapter, we will see whether anecdotal evidence is supported by research findings. To what extent can we predict differences in the success of second language acquisition in two individuals if we have information about their personalities, their general and specific intellectual abilities, their motivation, or their age?

Activity
Characteristics of the good 'language learner'
It seems that some people have a much easier time of learning languages than others. Rate of development varies widely among first language learners. Some children can string together five-, six-, and seven-word sentences at the same time that other children are just beginning to label items in their immediate environment. Nevertheless, all normal children eventually master their first language.
All of the characteristics listed above can be classified into five main categories: motivation, aptitude, personality, intelligence, and learning style. However, many of the characteristics cannot be assigned exclusively to one category. For example, the characteristic `is willing to make mistakes' can be considered a personality and/or a motivational factor if the learner is willing to make mistakes in order to get the message across.

Research on learner characteristics
Perhaps the best way to begin our discussion is to describe how research on the influence of learner characteristics on second language learning has been carried out. When researchers are interested in finding out whether an individual factor such as motivation affects second language learning, they usually select a group of learners and give them a questionnaire to measure the type and degree of motivation. The learners are then given a test to measure their second language proficiency. The test and the questionnaire are both scored and the researcher investigates whether a learner with a high score on the proficiency test is also more likely to have a high score on the motivation questionnaire. If this is the case, the researcher usually concludes that high levels of motivation are correlated with success in language learning. A similar procedure can be used to measure the effects of intelligence on second language learning through the use of I Q tests.
Although this procedure seems straightforward, there are several difficulties with it. The first problem is that it is not possible to directly observe and measure qualities such as aptitude, motivation, extroversion, or even intelligence. These are just labels for an entire range of behaviours and characteristics. Furthermore, because characteristics such as these are not independent, it will come as no surprise that different researchers have often used the same labels to describe different sets of behavioural traits.