Lenneberg's Critical Period Hypothesis

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 eithe r 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 quo te 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). On page 152, Lenneberg differs between aphasia patients before and after teens. Here,

children older than 12 are said to be incapable to regain their speech ability fully.

Mostly, Lenneberg uses the word “puberty”, so that the widely accepted interpretation of the critical period appears sensible at the first sight. There is evidence that the primary acquisition of language is predicated upon a certain developmental stage which is quickly outgrown at the age of puberty (142). Children may show steady improvement over a period of several years, but usually not after puberty (146). After puberty, the ability for (…) adjustment to the physiological demands of verbal behaviour quickly declines. Foreign accents cannot be overcome easily after puberty (176). On page 178, Lenneberg says that the cerebral lateralization becomes fully established about puberty and talks about a limitation to the acquisition of primary language around puberty.

These statements are quite ambiguous. Firstly, the period of puberty is different for every singular person. Secondly, it starts (on the average) later in males than in females. And finally, the end of this period is – according to over twenty different Internet sources and a couple of lexicons – somewhere between 14 and 21 years, dependent of when it is said to be over: as soon as sexual reproduction first gets possible or only after physical growth stops and the physical maturity is achieved completely. Lenneberg himself suggests that puberty starts at the age of fourteen – the time it takes to reach puberty (…), that is the first 14 man-years (171); this figure reappears on the page 155: progress in language development was only recorded in children younger than fourteen. Not only the term “puberty” is inherently very relative - Lenneberg blurs it even more by using word like usually, around and about and the constructions cannot be overcome easily, quickly outgrown or quickly declines. “Quickly” may mean immediately a s well as after a year. The following sentence is no more exact: By the time of puberty, a turning point is reached (150). That only means that at a certain point during this period - which lasts many years – a development towards less or no flexibility of the brain starts; the reader gets no information about when this development is supposed to finish. Or page 168, we read that puberty marks a milestone for (…) the facility in language acquisition. Terms like milestone and turning point