Of course, as we saw in Chapter 2, it is difficult to compare children and adults as second language learners. One of the difficulties in making the comparison is that the conditions for language learning are often very different. Younger learners in informal language learning environments usually have more time to devote to learning language. They often have more opportunities to hear and use the language in environments where they dc not experience strong pressure to speak fluently and accurately from the very beginning. Furthermore, their early imperfect efforts are often praised or, at least, accepted. On the other hand, older learners are often in situations which demand much more complex language and the expression of much more complicated ideas. Adults are often embarrassed by their lack of mastery of the language and they may develop a sense of inadequacy after experiences of frustration in trying to say exactly what they mean.

The critical period hypothesis has been challenged in recent years from several different points of view. Some studies of the second language development of older and younger learners who are learning in similar circumstances have shown that, at least in the early stages of second language development, older learners are more efficient than younger learners. In educational research, it has been reported that learners who began learning a second language at the primary school level did not fare better in the long run than those who began in early adolescence. Furthermore, there are countless anecdotes about older learners (adolescents and adults) who have reached high levels of proficiency in a second language. In neurological research, it has not been demonstrated that the hypothesized changes take place in the brain at puberty. Much research seems rather to suggest that the brains of very young infants already have some areas which are specialized for processing language. In the following pages, we will review some of the important recent studies designed to investigate the critical period hypothesis as it relates to second language learning.

C P H : More than just accent?
Most studies which have investigated the relationship between age of acquisition and second language development have focused on learners' phonological (pronunciation) achievement. In general, these studies have concluded that older learners almost inevitably have a noticeable `foreign accent'. But what of other linguistic features? Is syntax (word order, overall sentence structure) as dependent on age of acquisition as phonological development? Do older learners ever achieve native-like mastery of syntax? What about morphology (for example, grammatical endings which mark such things as verb tense or the number and gender of nouns)? One study that attempted to answer these questions is that of Mark Patkowski (1980).

Mastery of the spoken language
Mark Patkowski studied the effect of age on the acquisition of features of a second language other than accent. He hypothesized that, even if accent were ignored, only those who had begun learning their second language before the age of 15 could ever achieve full, native-like mastery of that language. Patkowski examined the spoken English of 67 highly educated immigrants to the United States. They had started to learn English at various ages, but all had lived in the United States for more than five years. The spoken English of 15 native-born Americans from a similarly high level of education was also examined. Their speech served as a sort of baseline of what the second language learners might be trying to attain as the target language. Inclusion of the native speakers also provided evidence concerning the validity of the research procedures. A lengthy interview with each of the subjects in the study was tape recorded. Because Patkowski wanted to remove the possibility that the results would be affected by accent, he did not ask the raters to judge the tape-recorded interviews themselves. Instead, he transcribed five-minute samples from the interviews. These samples (from which any identifying or revealing information about immigration history had been removed) were rated by trained native-speaker judges. The judges were asked to place each speaker on a rating scale from 0, representing no knowledge of the language, and 5, representing a level of English expected from an educated native speaker.

The main question in Patkowski's research was: `Will there be a difference between learners who began to learn English before puberty and those who began learning English later?' However, in the light of some of the issues discussed above, he also compared learners on the basis of other characteristics and experiences which some people have suggested might be as good as age in predicting or explaining a learner's eventual success in mastering a second language. For example, he looked at the relationship between eventual mastery and the total amount of time a speaker had been in the United States as well as the amount of formal E s L instruction the learner had had. The findings were quite dramatic. Thirty-two out of 33 subjects who had begun learning English before the age of fifteen scored at the 4+ or the 5 level. The homogeneity of the pre-puberty learners seemed to suggest that, for this group, success in learning a second language was almost inevitable (see Figure 3.1). On the other hand, there was much more variety in the levels achieved by the post-puberty group. The majority of the post-puberty learners centred around the 3+ level, but there was a distribution of levels (see Figure 3.1). This variety made the performance of this group look more like the sort of performance range one would expect if one were measuring success in learning almost any kind of skill or knowledge.