Interpreting Age Effects in Second Language Acquisition

1
Interpreting Age Effects in Second Language
Acquisition
David Birdsong

• A presentation of David Birdsongs chapter from
  the Handbook of Bilingualism Psycholinguistic
  Approaches edited by
• Judith F. Kroll and Annette M.B. de Groot

David Counselman Final Project APLNG 591 SLA
December 11, 2006
2
Introduction

• There is an undeniable, general correlation
  between age and skill at picking up a foreign
  language.
• Many have contributed this to a critical period.
• This is reasonable, considering some other
  evidence from science

3
Cont

• For example, there is a timetable associated with
  song learning in some birds (Marler 1991)
• Also, for vision in cats to develop fully,
  stimulation must be exposed to the visual cortex
  within the first three months of age (Hubel and
  Wiesel 1965)
• However, some researchers arent convinced that
  language acquisition is subject to a similar
  critical period.

4
Outline

• A general orientation to typical methodologies in
  SLA age factor research
• A view of temporal and geometric features
  characteristic of critical periods
• More specific data found within SLA research on
  the age problem
• The question of native-like performance and how
  it relates to the slope of the age-function
• Determining the slope of the age function
• Concluding remarks

5
The Age Question in SLA Research

• Often, as well as in this chapter, the age
  variable is the age of arrival (AoA) into the
  culture of the L2
• The issue of the end state
• Researchers usually set a bottom cut-off point
  for Length of Residence (LoR) like 10 years
• Usually, the issue is the following
• How does AoA affect L2 attainment or competency?

6
Cont

• Specifically, these are run experimentally in the
  laboratory
• subjects are asked to complete any of various
  tasks used to rate language competence.
• Results vary depending on setting, methodology,
  etc.
• Even presentation of material (orally vs
  visually) can make a difference (Bialystok and
  Miller 1999, Johnson 1992)

7
Cont

• This brings up an important fact
• The function of the effect of age will vary
  depending on the area of the L2 grammar being
  considered (e.g. Bialystok and Miller 1999,
  Birdsong and Flege 2001).
• Linguistic feature, amount of L2 use, and L1-L2
  pairing have all been found to play a role as
  well (see Flege, Yeni-Komshian Liu 1999, Moyer
  1999, Scovel 1988, Seliger 1978)

8

• Research has also looked at neurological
  dimensions of the issue, although these issues
  are not considered in detail in this article.
• Event-related brain potentials, fMRI, and
  positron emission tomography, for example.
• Also, do polyglots engage distinct neurological
  substrates in processing/ representing each
  language?
• Some evidence converges to say that high levels
  of L2 attainment correlate with the use of a
  common neurofunctional organization for the L1
  and L2 (see Brovetto 2002 for further discussion
  of this issue).

9
Geometric and Temporal features of Critical
Periods

• Generally, a critical period refers to a
  temperal span during which an organism displays
  a heightened sensitivity to certain environmental
  stimuli, the presence of which is required to
  trigger a developmental event.

10

• Some people assume the degree of sensitivity is
  constant throughout this temporal span (as
  pointed out by Bornstein 1989 183), which would
  imply

11
This view will be taken here

• Bornstein (1989) also noted, however, that a
  critical period, by definition, includes the time
  during its onset and offset, and so the function
  should look like this

12
A CP for language acquisition

• Since sounds like ba and pa can be
  distinguished by newborns a few hours old (Eimas,
  Siqueland, Jusczyk Vigorito 1971), it can be
  argued that the onset essentially begins at
  birth.
• Most accounts consider full adult-like competence
  to be possible if language learning begins by 4
  to 7 years of age. The beginning of the offset,
  could, therefore, be roughly located around this
  age.

13
Cont

• It is argued (Johnson and Newport 1989) that
  critical period effects for language acquisition
  should end around the point of complete
  neurocognitive maturation, roughly in the
  mid-to-late teens.
• This could be the end of the offset of the CP.

14
This provides the following
15
Other possible age-functions

• No end point the decline in attainment of
  language continues throughout the lifespan.

All of these functions will be compared with the
CPH (Lenneberg 1967) and with observations found
in the SLA literature.
16
CPH in the context of SLA

• The CPH has been formulated in various ways
• Increasing age entails
• Decreasing neural plasticity in the relevant
  cortical areas (Lenneberg 1967, Pulvermüller
  Shumann 1994)
• Loss of access to the language learning faculty
  or universal grammar (Eubank Gregg 1999)
• A gain in information processing capacity that
  might be ill-suited to the task of language
  acquisition (Newport 1991)
• Dismantling of relevant cortical circuitry
  (Pinker 1994)
• Loss of function of mediating mental faculties
  from lack of use (Bever 1981)
• The inhibition of learning by entrenched L1
  knowledge (Marchman 1993)
• See Birdsong (1999) for further discussion.

17
The function described by a CP

• Pinkers proposal (1994 293-294) is the only one
  that makes claims for the end of the offset,
  thereby fitting the function for critical
  periods, which has already been shown
• Pinker proposes that once the faculty to learn
  language has completed its task (once weve
  reached puberty and have learned our L1), it gets
  discarded to save metabolic energy. (liked to
  floppy disk)

18

• Johnson and Newport (1989) make a similar
  proposal (which fits the geometric and temporal
  features of a CP), but without mention of the
  same set of neural and metabolic mechanisms as
  Pinker.
• Other proposals do not predict a leveling off at
  the end of the critical period, and therefore
  cannot define a CP function, but well see that
  these proposals arent unworthy, they in fact
  seem to be even closer to reality.

19
Behavioral Data

• The primary argument against the CPH is that the
  data regularly fail to show a leveling off that
  signals the end of the CP.
• If language learning is related to maturation,
  there isnt any maturational difference in a 17
  y/o and a 27 y/o, so the CPH claims that people
  of both ages should reach the same level of
  attainment (Johnson and Newport 1989 79)

20
Straight-line Age Effects

• Flege (1999) reanalyzed data from Flege et al.
  (1995) to show that there was no discontinuity in
  ratings of perceived foreign accent as
  a function of age.

21
Cont

• Flege (1999) also reports that in Yeni-Komshian,
  Flege Liu (1997), there was also no evidence of
  a break in linearity.
• Hakuta, Bialystok Wiley (2001) found the same
  type of linear function when analysing the 1990
  U.S. Census results, which included self reports
  of Chinese and Spanish immigrants English oral
  proficiency.

22
Cont

• Bialystok and Hakuta (1999) looked at a subset of
  these immigrants who had LoR of at least 10 years
  and whose AoR ranged from 0 60
• Again, theres a linear trend in the data
• The results of these analyses

23
Chinese Spanish
24
Cont

• Flege et al. (1999) also found no evidence for a
  discontinuity in accent ratings of 240 Korean
  immigrants
• but DID find a slight discontinuity in their
  scores on a 144-item test on knowledge of English
  morphosyntax.
• However, even late-arriving Koreans were subject
  to a negatively-sloping fuction of age.

25
Disaggregation Analyses

• These analyses, in which age groups are divided
  at some age near puberty or a little after, often
  show a discontinuity in the slope of the age
  function.
• Patkowski (1990), for example, analysed his 1980
  dissertation data by dividing his subjects into
  early (younger than 15) and older (older than 15)
  learner groups
• Early arrivals regression line .052
• Late arrivals regression line .028

26
Johnson Newport (1989)

• Used this method
• Results provided evidence in favor of the CPH
• Birdsong and Molis (2001) replotted the JN89
  data and proved different results.
• BM01 also replicated the JN89 study with
  Spanish natives, and obtained a totally observe
  pattern.

27

• Here, the dotted line, JN89 shows a decline in
  early stages and a leveling off near the end
  (CPH)
• But BM01s replication of the study shows
  different results, in which there is a ceiling
  effect for early learnings and then a continuous
  decline after age 16.

• There is no patten here for the late arrivals.
• While this doesnt provide evidence for what the
  function may look like, it definitely does not
  provide evidence for a leveling off and bottoming
  out of the function in late arrivals.

28
Cont

• Also interesting, and important, is that
  Bialystok Hakuta (1994) reanalyse the JN89
  data
• and find that by moving the age of arrival
  split to 20 years of age
• the linear correlation of late arrivals
  increased to significance.

29
Summary from the data

• Some studies show a steady continuous decline in
  language attainment as a function of age.
• Others show that there is a discontinuity, where
  the slope for the late arrivals is much steeper
  than for early arrivals.
• In either case, there is NO evidence for a
  flattening out of attainment, which rejects the
  notion of an endpoint to the decline of
  sensitivity at some age after puberty.

30
The functions we looked at

• These results do not support the function
  associated with the CPH. Results that suggest a
  discontinuity look more like graph C, while other
  studies resemble the graphs A or B, depending.

31
Nativelike Attainment

• In the experimental context, usually defined as
  falling within the range of native speakers
• Some researchers strictly define that
  nativelikeness must fall within one standard
  deviation of native speakers.
• Some argue (Long 1990) that if late learners
  achieve nativelike scores on experimental tasks,
  this provides evidence to refute the CPH.

32
Cont

• In earlier research, evidence for this was not
  found.
• In latter research, however, much evidence of
  this type has been found.
• It is interesting though that most late learners
  who fall within nativelike ranges are usually
  earlier late learners (late teens).

33
Cautions should be considered

• Both the native speaker and immigrant subjects
  should be taken from the general population, and
  not the cream of the crop
• Some L2 speakers have had varying degrees of L2
  exposure prior to immigration.
• The L2 sample should be controlled to make sure
  subjects are at or near the end-state. (2 years
  VS 25 years)

34
Other problems implications

• It can also be problematic to compare any
  bilingual to a monolingual native-speaker group.
• A bilingual is not two monolinguals in one
  (Grosjean 1989)
• Previous studies that have claimed 5 or less of
  the population reaches native-like proficiency
  (Bley-Vroman 1989, Selinker 1972) may not have
  been sampling the right group of people.

35
Nativelike Attainment and the Age Function

• It should be considered that the likelihood of
  nativelike attainment in latter ages is subject
  to the slope of the age function.

• Steep slope implies less chance of nativelike
  attainment in older ages.
• Shallower slope implies more chance.

36
Age and Other Factors

• If the slope of the age function is so crucial to
  determining the likelihood of attaining
  nativelike competence
• how can we determine the slope?
• what affects the slope the function?
• what exactly does the function look like?

37
Cont

• Years of education have been found to play a role
  (Bialystok and Hakuta 1999)
• Greater use of the L2 has correlated with less
  perceived foreign accent (Flege colleagues)
• A variety of other cognitive, task-related,
  attitudinal, experiential, demographic, aptitude,
  and training variables may affect the slope as
  well.

38
Different aspects of linguistic knowledge

• It is also important to note that the age
  function does not affect all areas of language
  competence the same (Eubank and Gregg 1999, Flege
  et al. (1999), Flynn and Manuel (1991), Seliger
  (1978), and others).
• For example, Birdsong and Flege (2001) found that
  increasing AoA did not affect accuracy of
  knowledge of regular verb forms in English, but
  it did affect the knowledge of irregular verb
  forms.

39
(No Transcript)
40
Declarative VS Procedural Memory

• Birdsong (2004) suggested that the effect of
  aging on declarative memory is likely a big issue
  here.
• Declarative memory declines much more with age
  than procedural memory does.
• This distinction should also be considered, when
  trying to understand the age function on language.

41
Conclusion

• The observations observed in this chapter
  illustrate evidence that the age function does
  not match the predictions of the CPH
• Degree of L2 attainment does not appear to be
  linked to maturational milestones, but rather
  with age in general.
• The likelihood of native-like attainment
  decreases throughout the age spectrum (not does
  level off) progressively.

42
Cont

• Not everyone experiences this decline to the same
  degree or at the same pace.
• Whatever it is that allows language acquisition
  (brain plasticity?) is not one thing that affects
  the global mechanism for language learning
• age affects the acquisition of various
  linguistic features differently (regular vs
  irregular, for example).

43
Closing remark

• Flege opened and closed his plenary speech (age
  effects on L2A) at the Conference on Hispanic
  Linguistics and Acquisition by saying
• I hope you now understand less about the effect
  that age has on language acquisition than you did
  before the presentation.

44
References

• Bever, T. G. (1981). Normal acquisition
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