According to Dr. Harley, what makes language learning more difficult after a certain age?

W: Good morning, Dr. Harley, thank you very much for coming on our radio talk. We know that you are an applied linguist, specializing in second language acquisition.
M: Right.
W: So, today, we’ll look at this issue. Now, first, Dr. Harley, could you please tell us what is second language acquisition?
M: Well, second language acquisition is, happens when a child or adult has already become competent at a language, and then, um, they attempt to learn another.
W: Okay, most people think, including me, it is difficult to learn another language. What are the reasons? Why is it so?
M: Well, there are a number of reasons for this. First, there have been research studies, they have shown that some aspects of language learning, especially syntax, are more difficult beyond a certain age, say after around twelve years of age. (1)
W: So age plays an important role in language learning?
M: Yes. But that’s not the only reason.
W: Oh, is that so?
M: Yes, for example: time and interest. Old children and adults often have less time and motivation to learn a second language. Another is related to the similarities and differences between one’s mother tongue and a second language. We find that learners will experience difficulty when their mother tongue and the second language they are learning differ. In general, the more idiosyncratic a feature is in a particular language, relative to other languages, the more difficult it will be to acquire.
W: Perhaps this is the key issue. Differences between languages cause language-learning problems.
M: Well, this may be one of the issues here, but this cannot be the whole story, as not all differences between languages cause difficulty. Let me give you an example.
W: Okay.
M: Research has found that many errors by Czech speakers learning English were made on syntactic constructions in which the two languages do not differ. (2)
W: Oh, really. The picture is more complicated than we’ve imagined.
M: Definitely yes. Each language-learning situation is different, so reasons vary a lot from case to case.
W: Now, Dr. Harley, since learning a second language is a difficult process, you know in one way or another, are there any methods so far, effective methods, to teach a second language.
M: There again, no method is absolutely effective in all situations. Some may prove effective, others may not, I mean all depending on specific conditions. But generally speaking, there are a number of methods that have been used to teach a second language.
W: Could you mention a few?
M: For instance, there is the traditional method. This method is based on translation from one language to another, and it emphasizes grammar teaching. (3) And then you have direct methods, which focus on conversational skills, and all teaching must be carried out in the second language.
W: Oh, I see. Any other methods?
M: Yes. For example, the audio-lingual method. This method emphasizes speaking and listening before reading and writing.
W: How interesting.
M: Then you have the immersion method. This method teaches learners exclusively through the medium of the second language.
W: How?
M: Well, it simply means that you cannot speak mother tongue. Everything must be done in the language you are learning. To me, the most natural method of learning a new language is what I call "submersion," that is to go to that country and be surrounded exclusively by speakers of that language.
W: Thank you very much Dr. Harvey, for introducing some of the language teaching methods. Now, let’s move on to something a bit theoretical. Since second language acquisition and teaching are a fascinating area for researchers, are there any theories to explain second language acquisition.
M: Yes. Many theories and models have been put forward by researchers so far. Today, I’d like to mention the five hypotheses proposed by Steven Krashen.
W: Okay.
M: The five hypotheses form what he calls the "Monitor Model" of second language learning.
W: What does it mean?
M: Okay. The first hypothesis is the "Acquisition and Learning Distinction" hypothesis. According to Krashen, children acquire their first language largely unconsciously and automatically. But, adults could only learn a second language consciously and effort fully. And adults could indeed acquire the second language, at least in part.
W: Right, then what’s his second hypothesis?
M: His second hypothesis is the "Natural Order In Acquisition" hypothesis. Basically, he means that the order in which learners acquire syntactic rules is the same in both languages.
W: Oh, that’s something really new to me.
M: The third hypothesis is the "Monitor" hypothesis, which is central to his theory. Here again, we come across the distinction between acquisition and learning. According to this hypothesis, the acquisition processes create sentences in the second language, right? But learning enables the development of a monitoring process to check and edit this output. The monitor uses knowledge of the rules, that’s why, as I said just now, learning is a conscious process.
W: This means in learning you use knowledge of the language to make sure what you say or write is correct. Is that so? (4)
M: Yes. His fourth hypothesis is the "Comprehensible Input" hypothesis. In order to move from one stage to the next, the learner must understand the meaning and the form of the input. This emphasizes the role of comprehension. And finally, the "Active Filter" hypothesis. This suggests attitude and emotional factors are also important in second language acquisition.
W: I guess Krashen’s model has provided a useful framework for second language learning.
M: Yes, it indeed has. And, it has also proved to be one of the most influential theoretical approaches to teaching a second language.
W: Okay, Dr. Harley, thank you once again for talking to us about second language acquisition.
M: Pleasure.