The Practical Linguist / What ever happened to the critical period?
Marshall R. Childs Special to The Daily Yomiuri
Two columns ago ("Get your mind in the mood for languages," April 13), I wrote that, as children mature into adults, there is no "critical period," if critical period describes a fertile period for language learning that is followed by a sharp decline in language-learning ability. Instead, I said, there is simply a progressive decline from birth to death. That declaration brought some readers to their keyboards.
"What ever happened to the critical period?" several readers asked. Many had learned this phrase as an explanation for the fact that most adults do not learn a second language well. Today I want to persuade you that the notion of a critical period is simplistic and does not fit the facts of human language learning.
The term "critical period" is borrowed from the field of ethology, and finds its inspiration in the fact that some newborn birds have a several-day period during which they will fix upon any moving object as their mother. Austrian ethologist Konrad Lorenz (1903-89) studied greylag geese, and found that if he substituted himself for a mother goose, the goslings accepted him and followed him around faithfully.
Lorenz called the goslings' behavior! "imprinting," and said the animals were biologically programmed to react to environmental stimuli during a certain "critical period."
The biological process of the several-day period during which a duck can identify its mother, although complex in itself, is much simpler than human language learning, and is not a useful analogy. First-language learning lasts at least two decades and entails many complex developmental processes that unfold at different times. It affects different people differently--leaving a few adults who are relatively successful at learning new languages.
===
First-language learning
First-language learning is a complex process that begins in utero and extends actively into the teenage years and beyond. The several aspects of language learning develop most strongly at different times, but the result is a holistic process that is a part of successful participation in a language community.
Neurological development begins before birth and, together with hearing and speaking, is substantially in place after toddlerhood. The ability to communicate within one's language environment is sought by very young infants and is fairly well adapted to the social setting by the time the child begins first grade. Apprehending a common definition of reality and mounting a personality proceed strongly from toddlerhood to the teenage years, and personality development goes through phases in which social dependency is transferred first from family to peers and then to the whole community.
Prof. James Hurford of the University of Edinburgh in Scotland imagined that a language might be said to have size, and "that children proceed from knowing 'some' of a language to knowing 'all' of it." The description of aspects of language learning in the previous paragraph suggests some elaboration of Hurford's image. Language learning is never completely finished. Each aspect, proceeding at its own pace, seems to approach a plateau without ever reaching it.
We would love to be able to say that hearing is 90 percent fixed by age 3, that full participation in a conversation is 90 percent fixed by age 7, or that vocabulary is 90 percent fixed by age 18. Although precision of this sort is impossible, the evidence is strong that different aspects of language learning take place over different periods of development. If we were to believe in critical periods at all, we would have to declare that there is not one critical period for language learning, but many.
Because a critical period exists in only a very gross sense, research that treats it as a unitary phenomenon is unlikely to have lasting value. A more economical approach to the facts would acknowledge the complexity of language learning as well as its intimate connection with other kinds of learning (social, personal, etc.). In this approach, we would note that language learning proceeds, just as Hurford said, from a skill of a small size to one of a very large size indeed.
But the vision of the continuous enlargement of one's first language or languages has a severe implication for new languages that might be presented. In a sense, there is only one barrier to adult second-language learning, and that is that a first language already occupies the language place.
I don't mean that the brain is filled with language like a balloon and can accept no more languages. Actually, it can accept many more if we can figure out how to slip them in. I mean that the automatic neural pathways are increasingly set to interpret any language input as conforming to known languages. New languages tend to get locked out simply because they do not match subconscious preconceptions.
===
Continuous decline
Imagine a curve of skill in known languages, rising from birth to death. Hurford might call this curve an indicator of the size of language knowledge. Now, however, note that the space above the rising curve is steadily diminishing. That is a suggestion that, for most people, the ability to learn new languages decreases as we get better at the languages we already know.
The term "critical period" implies that there is an age beyond which something is virtually impossible. Critical periods do exist in many biological realms. Language-learning ability, however, suffers a continuous decline from birth to death. For this reason, we should use a term such as "maturational constraints" rather than "critical period" to refer to human experiences of language learning.
In 2003, Kenneth Hyltenstam and Niclas Abrahamsson of Stockholm University published a book chapter on "Maturational constraints in SLA [Second-Language Acquisition]." These authors wrote that there is no sudden decline in language-learning ability. Instead, there is a continuous decline that begins at birth as the brain adapts itself to the languages in the environment.
Hyltenstam and Abrahamsson claimed that no one who begins learning a second language after childhood can achieve the skill of a native speaker. Therefore, "language learning must start 'from the beginning' in order to result in full nativelike ultimate proficiency." Some adults develop amazing skill in a second language, but deficiencies can be identified "in the laboratory of the linguist with a special interest in second language-learning mechanisms."
The clear consequence of a continuous decline is that, if you want to learn a second language, the earlier you start, the more thoroughly you can learn it. But because the decline in learning ability is continuous, there is no particular age beyond which the effort is hopeless (that observation offers some comfort to old guys like me).
A few people continue to have a vested interest in the concept of a sharp decline in language-learning ability. Some people like the metaphor that we are born with Language Acquisition Devices (LADs) in our heads. They tend to see the "critical period" as evidence that LADs are consumed in the process of first-language learning--and so are not available for learning further languages.
Some people see the critical period as a bastion for defense against the incursion of powerful international languages such as English. These people reason that if they can just fend off a foreign language until the end of the critical period (for example, the end of primary school), students will not learn the foreign language well and the heritage language will be preserved.
The phrase "critical period" has staying power because it is fixed in the minds of many people. But the image of a sharp decline in ability is bound to be replaced (mercifully) by the image of a gentler decline. And the new conception is a useful baseline for research studies of adults who continue to learn languages well in spite of their age.
* * *
Send e-mail to childs@tuj.ac.jp. The column will return on July 6.
(Jun. 8, 2007)