Are there perhaps specific biological foundations for language acqui- sition which are linked to a particular period of time during brain develop- ment (a “critical” or “sensitive” period), analogous to some species of bird song acquisition? (e.g., Marler 1987).
20. Critical Period
A period of time with a distinct onset and offset during which experience can lead to learning by an organism; assumed to be innately programmed and irreversible.
Puberty has sometimes been posed as “offset” time for language acquisition, potentially linked to development of hemispheric dominance.58
Given the findings above (5.3.3), there is not a simple basis for a clear bio- logical definition of a Critical Period for language acquisition in terms of hemi- spheric asymmetry and lateralization. To test the hypothesis of a critical period, researchers may look for cases where language experience has not occurred until post-puberty. Several relevant cases exist, such as Genie (Curtiss 1977).59These cases may involve extreme deprivation and are complex and confounded. Another form of evidence would involve adults acquiring a second language later in life.60 In keeping with the hypothesis of a Critical Period for human language acquisi- tion, some researchers have proposed that:
21. “. . . adults no longer have access to UG for the second language acquisition process” (Schacter 1990).
None of these forms of evidence are conclusive, however.
57See Kolk 2000 for review of “multiple routes” to brain plasticity. There are limits to plasticity:
Curtiss et al. 2001; St. James-Roberts 1981; Gazzaniga 1977.
58See Lenneberg 1967, 158; Penfield and Roberts 1959. There is considerable disagreement as to hypothesized time of offset. Lenneberg’s early hypothesis does not refer to the ability to acquire language knowledge, but rather to the physiological components connected with “verbal behaviour” (1967, 158).
59Also: Chelsea (Curtiss 1977), Isabelle (Brown 1958), EM (Grimshaw et al. 1998).
60Mayberry 1993; Newport 1990. Hypothesis of a critical period for language acquisition is more complex than first appears. If the human brain is biologically programmed to include a Language Faculty, this may exist continuously once formed, as does the brain’s biologically determined faculty for vision. A critical period is not necessary for bird song acquisition; some species can repeat the song learning process indefinitely as adults (Brainard and Doupe 2002).
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5.8.1 Genie
The tragic case of “Genie” is important to these issues because of the relatively precise and extensive linguistic and cognitive analyses which it has received (Curtiss 1977, Curtiss et al. 1974).
Born in 1957, Genie experienced extreme deprivation beginning at about twenty months of age when she was confined to a dark room in the back of a house, harnessed to a potty seat by day and strapped in a sleeping bag in a caged crib at night, until she was discovered in 1970 at the age of 13.9. She was exposed to little or no auditory stimulation during confinement, and beaten when she made sounds. Genie’s language experience during confinement was thus thought to be minimal to non-existent.61 Her father barked and growled at her; her mother, going blind, was allowed minimal contact with her children. When discovered, Genie appeared to be about six or seven years old, weighed 59 pounds, was mal- nourished, incontinent, had difficulty standing and walking, could not chew solid food, and never spoke. She appeared to understand only a few words.
With physical nourishment and various attempts at personal, social and cog- nitive nourishment, Genie’s physical development quite quickly brought her into puberty. Her general cognitive development reached the six- to eight-year level by the next year, when she was fourteen. At the same time, Genie’s language devel- opment, particularly its syntax, appeared extremely deficited. After five months she began to use single words and her vocabulary grew quickly. Her first words were often cognitively complex, e.g., color and number words and superlatives.
Two words were combined and then three to four words, e.g., (22); after about two years, attempted recursion appeared, e.g., (23).
22. want milk
Genie love Curtiss big elephant long trunk 23. ask [go shopping]
tell [door lock]
However, a complex of coherent linguistic deficits continuously characterized the syntax of Genie’s language (table 5.4). The nature of these deficits suggests the absence or malfunction of a Language Faculty. They all reflect incompetence for relating a surface form with an underlying form, i.e., to relate distinct levels of representation in ways required by natural language (chapter 2). Accordingly, Genie’s language lacks structure dependence; attempts at recursion in her lan- guage are deviant, as in (24a)–(24b).
61Little is known of Genie’s history before her confinement. Medical records exist for a blood transfusion at birth during a Caesarian birth, and a normal birth rate of seven pounds. However, her mother reported that she did little cooing or babbling and showed certain developmental lags.
Records also indicate a splint for congenital hip dislocation at four months, a weight of only fourteen pounds at six months, and only seventeen pounds at eleven months, and at fourteen months an acute illness involving fever, unresponsiveness and “possible retardation.”
Table 5.4 The case of Genie: a complex of linguistic deficits (derived from Curtiss 1977).
r Word order problems
Inability to deal withword order variationin production and comprehension
“There are no rules permuting sentence constituents” (196) r Failure withquestion formation; “where cracker” (163)
No subject–aux inversion, as in “Do you have a cracker”
r Nocontractions
r Noauxiliariesin Inflectional Phrases of sentences: “Idohave a candy”
r Irregular and optional application of inflectional endings: both “Curtiss is dance”
and “Curtis is dancing”
r Difficulty withpronounsof all forms
24. a. I want mat is present (19 March 1975)
b. Father hit Genie cry long time ago (2 May 1975)
In these constructions, the linear series of one proposition is simply juxtaposed with that of a second. A single noun functions both as the object of the first, and the subject of the second proposition, without embedding.
25. a. S - V - O - V - O
b. Father hit [Genie] cry long time ago
Genie predominantly used her right hemisphere for language (and, to a lesser degree, for non language).62
One possible explanation for Genie’s failure with language is that after a crit- ical period the left hemisphere can no longer control language acquisition, “.
. . accounted for by a kind of functional atrophy of the usual language areas, brought about by disuse (due to inadequate stimulation) or suppression” (Cur- tiss 1977, 216). Another possibility is that Genie’s brain function is related to brain damage which may have at least in part existed prior to her confine- ment. In the absence of full medical records, it is not possible to conclusively choose between these. This, plus the massive damage caused to all aspects of Genie’s development by her horrendous confinement, make it difficult to view this case as conclusive in evaluating a Critical Period Hypothesis for language development.
Genie’s case does provide converging evidence on the internal modularity of language organization, however. Genie’s relatively fast development of complex lexical knowledge, combined with her fundamental deficits in syntactic knowl- edge, once again demonstrate the dissociation of these components.
62This was determined through dichotic listening, tachistoscopic tests and ERP analyses (Curtiss 1977, 213). In many ways, Genie’s language is consistent with the language of RH adults: com- misurotomy and/or hemispherectomized (Curtiss 1977).
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5.8.2 Second language acquisition
The proposal in (21) remains the center of intense debate.63Clearly, there are differences between child and adult learners of a language. Yet age alone does not necessarily involve loss of ability to acquire another language.
In some cultures, adult acquisition of second languages is commonplace.64 (a) A substantial proportion of adults do acquire accent-free speech when acquir- ing another language, (b) while some child learners do show an accent. (c) Adults can be trained on foreign phonological distinctions; (d) some non-native sound distinctions are maintained while others are lost. Difficulties with spe- cific types of sounds or sound distinctions in a second language may relate to the grammatical system of the L1, not to a global loss of ability. (e) Funda- mental UG components, viz., linguistic principles and parameters, have been found to constrain adult second language acquisition as they do first. (f) Expe- rience and age must be dissociated in comparing first and second language acquisition.65
In order to evaluate the role of early language experience in later language learning, a recent study compared later language acquisition of American Sign Language (beginning between ages of 9 and 15) by two groups of subjects who had not been exposed to sign language at early ages. One group was born deaf and one was lately deafened, having experienced spoken language early in life. The group without early language experience showed low levels of per- formance with ASL, contrasting with the lately deafened. The researchers then compared three groups of adults on late acquisition of English: the first, born profoundly deaf, with little exposure to language before ASL exposure in school;
the second, born profoundly deaf but with experience in ASL in infancy; and the third, born hearing but having learned a language other than English in child- hood. Whether deaf or hearing, exposure to a language, whether sign or oral, resulted in superior performance on the late-learned language (English). The authors conclude that “the ability to learn language arises from a synergy between early brain development and language experience, and is seriously compromised when language is not experienced during early life” (Mayberry, Lock and Kazmi 2002, 38).
In summary, if there is a critical period for language acquisition, then its nature remains to be discovered. It very likely involves complex interactions between cerebral foundations and experience.
63Epstein et al. 1996 and related commentary; Singleton 1989 for review; Flynn and Manual 1992, Birdsong 1992, 1999; Newport 1990; Flynn 1996; White 1996.
64Singleton 1989 for review; Snow and Hoefnagel-Hohle 1978; Slavoff and Johnson 1995.
65(a): Seliger, Krashen and Ladefoged 1975; (b): Asher and Garcia 1969; White and Genesee 1992;
(c): Best et al. 1988; Flynn and Manuel 1991; (d): Best et al. 1988; (e): Flynn 1996; White 1996;
Martohardjono 1993; Flynn and Martohardjono 1994; Epstein et al. 1999; (f): Vinnitskaya, Foley and Flynn 2001.