Heinrich Heine-Universität
Anglistisches Institut
2. Semester

Lenneberg′s Critical Period Hypothesis

von: Alexandra Berlina

Contents

Introduction to the critical period theory 3

When does the critical period start and finish? 4

Russian accent in immigrants to Germany 7

Reference to Lenneberg 10

Conclusion 11

Literature 11

Introduction to the critical period theory

In his fundamental work, “Biological Foundations of Language”, the biolinguist Eric Lenneberg presents, among other things, his “Critical period” hypothesis. It consists, roughly, in the idea that a certain age is appropriate for learning a language, so that it is impossible to achieve full competence before or after it. In this essay, I will focus on the second borderline, which is usually drawn by later interpreters at the beginning of puberty – the reasonability of this will be discussed in the next chapter of this essay.

Lenneberg subdivides the ongoing process of lateralization into five levels: an infant up to 20 months has identical hemispheres without functional differences; a toddler up to 36 months develops a preference for either the right or the left hand, but the responsibility for language still can easily switch an other hemisphere; a child up to 10 years is still able to reactivate language functions in the right hemisphere; in the early puberty – up to 14 years – the equipotentiality rapidly declines, and after that it is lost completely. Lenneberg talks about a “reactivation”, not “creation” of the language function in the right hemisphere. He thereby implies that at the beginning this function is present in both hemispheres and later (partly) disappears from the right one; it does not develop in the left half of the brain only right from the start (with the option to migrate to the other hemisphere in emergency cases during the childhood). According to later studies, he was right in this point; apparently, he even overrated the monopolistic role of the left hemisphere as he wrote that in about 97% of the entire population language is definitely lateralized to the left (p. 181). He wrote the “Biological Foundations…” in 1967, ten years before the Russian scientists Balanov, Deglin and Chernigowskaya proved experimentally that every hemisphere contains certain speech ability: they caused a temporary aphasia of one hemisphere in healthy persons and detected that people with a blocked hemisphere were able to talk – even if it was the left one. In that case the used vocabulary shrunk, the test persons spoke very little, in short simple sentences, and only about concrete, visible objects, whereas persons with the right hemisphere blocked became very talkative, fantasized, used complicated grammatical constructions and a lot of abstract terms. Simultaneously, their intonation and pronunciation differed from the usual one, and their voice changed slightly. According to this experiment, the speech ability is based in both hemispheres, but only the left one is responsible for the ability to abstract the statements from the direct environment, which is regarded as one of the most important qualities of human speech and a cardinal distinct from the animal signals by the majority of linguists. Without this function the language ability is extremely constricted.

When does the critical period start and finish?

The critical period is normally referred to as the time before the onset of puberty. Is this definition right? Lenneberg does not express himself very clearly on the limits of this period. The chapter “Language in the context of growth and maturation” alone contains dozens of different statements about this point. I would like to quote some of them, arranged according to increasing ages mentioned.
Talking about aphasia patients, Lenneberg draws a first border at the age of four, and an other at the age of ten – in patients between four and ten years of age, the symptoms are similar to adult symptomatology, but (…) the overwhelming majority of these children recover fully (…) and some lines later he says that the period during which recovery from aphasia takes place may last much longer than in adult and that patients older than four and younger than ten (…) recover fully (p.146). Here, a child is said to loose the necessary flexibility of the brain with ten. And here with eight - if the lesion is confined to a single hemisphere, language will invariably return to a child if he is less than nine years old at the time of the catastrophe (p.151).

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