This course explores the brain bases of bilingualism by discussing literature relevant to differences in age of initial learning, proficiency, and control in the nonverbal, single language and dual-language literature. Participants will learn about the latest research related to how humans learn one or two languages and other cognitive skills.
5.11 Speech in a Second Language
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The Bilingual Brain
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Week 5
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Arturo E. HernandezProfessor
Psychology
[SOUND] Work in my laboratories also looked at
the connection between speech and proficiency.
Now you might recall speech and
age of acquisition have been linked quite strongly, right.
So accent, the ability to process certain types of
information is clearly linked to the age in which a language is acquired.
But the question that we need to answer, one that was brought up originally by
Flagen, and what is termed now the speech learning model, was that
some non-native speakers are able to learn to distinguish and produce speech.
We can argue about whether it's accented or not,
is it monolingual-like or not, but clearly the speech is intelligible and
their ability to process speech in a second language is possible.
And they can become quite good at having conversations.
The question is how does that happen?
Is that different in a late learner than an early learner?
So Achila Suarte, former graduate student, did a study in
which she looked at people rating how similar two sounds were.
We talked about this in terms of age of acquisition in an earlier section.
And the finding was that when you asked people to rate two
sounds as really similar, somewhat similar, somewhat dissimilar, or
really dissimilar, you find this effect,
such that what happens is that when people hear things like saf saf or saf sof
that essentially the monolinguals and the early learners have these four very
clear clusters for saf sof, suf, and sef.
The later bilinguals, right,
the later second language learners, start to show much more fuzziness.
It's as if they don't hear this quite particularly well.
And the question is, how do they distinguish between a saf and a sof,
if their clusters are fuzzier than those who learn it early in life?
And there's reasons that people who learn a language early in
life would have these very clear clusters.
One reason being that early phonological acquisition in the native
language transitions from hearing many different contrasts to
specific contrasts within that language.
And so what would happen is that he would get a very sharp tuning of
the perceptual system to hear a saf as a saf.
But what about somebody who's tuned to a slightly different system and
has to retune to English?
Well, in this case, the Spanish speakers that we took did re-tuning,
but they could still distinguish between saf and sof and
the way they did it is by comparing across different sounds.
So the later somebody learned a, a language,
the more they did this comparative process and in fact, the ability or
the distance between these two different clusters was actually reflected in,
or correlated with, their proficiency in that second language.
So the acquisition of this phonological system appears in
these adults to be different and to rely on different aspects of processing,
specifically comparison across different sounds.
This bears some resemble again to what's been done with regard to
musical pitch or absolute pitch being the recognition of a single note and relative
pitch being noticing the difference between notes, as a comparison process.
And similarly, it appears that late learners are comparing sounds, and
they know that a saf is not as of, or a suf is not a sof,
at least for the Spanish speakers.
And it's because they're able to compare across sounds.
And so, it's a, a more conscious, a more effortful process.
But it is one that can be done, and one in which, when used reliably,
can allow late learners to distinguish sounds in a second language.
In a similar vein, Achila Suarte looked at a group of
children that were acquiring a second language.
So these were children who were from Spanish-speaking homes,
learned English upon entering school.
And at about six to seven years of age when they were placed in the scanner and
asked to just listen to sounds,
what appeared as activity was within superior temporal gyrus.
Superior temporal gyrus is up in the temporal lobes.
It's an area involved in speech.
This is not surprising to find this.
It's been found in many, many studies.
The interesting thing is that these children were listening to English sounds.
They were in the process of learning English.
And they showed superior temporal gyrus.
A group of monolingual kids we tested also showed this activity within the superior
temporal gyrus in both the left and the right, just like the bilinguals.
In the group of older bilingual children, there was also activity in
the superior temporal gyrus, but other areas came online.
These areas included parts of the frontal lobe involved in control processing.
There were also areas in the parietal lobe,
also involved in controlled processing.
And the para-hippocampus gyrus in the area roughly involved in visual processing.
The fact that these other areas come online for this group of children,
suggests that there seems to be some readjustment process going on.
Again, the introduction of the second language has led to other areas being
recruited in order to, as adults now, when we look at brains of adults who
have gone through the same process, settle back roughly to superior temporal gyrus.
Although the bilingual adults, the Spanish-English bilinguals,
same type of acquisition, right, first Spanish, then English,
show these two areas as superior temporal gyrus,
some additional areas but not nearly anything like the eight to 11-year-olds.
The eight to 11-year-olds seem to be showing this very strong
area outside of superior temporal gyrus.
And the idea that this suggests is that,
in fact, when these children are very young, they're actually using
their native language system to interpret these English phonological items.
In a later phase, they begin to use other systems, in order to help
to recognize these sounds, and eventually settle back to superior temporal gyrus.
Although there's always a trace of the fact that this is a second language.
So it appears that there's a transition here from what looks like
reliance on native language systems, some adjustment between eight and
11 to processing using other areas that are involved in
more general types of control, and then a settling back to superior temporal gyrus
with always a trace left of the fact that this not the first language.
Archila Suarte has also followed this up
by looking at in adults the difference between age of acquisition and
proficiency, and there are differences.
Proficiency plays a role in the brain activity observed
during the processing of speech contrasts in a second language.
So age of, age of acquisition plays a role and proficiency plays a role.
Now if we think about the children, it's hard to dissociate those perfectly, right?
So age of acquisition influences proficiency and both of these play a role,
but they seem to work together as time rolls on.
So even though in this course we've considered them as separate factors,
it's pretty easy to realize that, in fact, these two factors interact across time.
And they play roles, and they, each one changes the other.
So again, in thinking about this, and in thinking about Petrie's role, and Ribose's
role, you have to realize it's a much more interactive type of system, and we'll
come back to this idea of interactivity when we get to the end of this course.
That's something I want you to keep in mind when thinking about
the bilingual brain.
So this section considered proficiency within the bilingual literature.
And we started with the case of this patient,
was a 22-year-old, acquired English at age 10 when she moved to the US and
had neurosurgery and had a loss in one language relative to the other,
essentially, a stronger decrement in Spanish relative to English.
And this was based on the Boston naming test.
Again, this tests a picture vocabulary.
Now, as I mentioned earlier, Kathryn Kohnert ran a group of bilinguals
that were, again, Spanish native speakers who learned English and
found very similar scores to the one shown by the patient.
And I think what this shows is that there's a lot of variability in language
proficiency across people who have similar types of age of acquisition.
Essentially you could think of this as a continuum, right?
Some people who have an early age of
acquisition end up having much higher proficiency in
their second language relative to others who had the same age of acquisition.
And we could argue and think about, possibly,
whether that has to do with something like how often they were exposed.
How much use they had over time.
And, and if we think about it that way, we could really think of it almost similar to
the way we thought about or talked about word frequency.
We could talk about language frequency.
Right.
How often they used it.
How often over time and whether all this use over time adds up and
creates better proficiency.
Is it something that has to do with experience?
We could also ask, on the other hand, whether it has something to do with
possibly whether some people have a higher capacity for language.
That's a difficult question to answer right here, but the point for
us right now is that this langauge proficiency is spread over time and
it varies across people.
And that in order for someone who sees a patient who may look like they
have a decrement in one language, in order to make the case that there's truly
a decrement, one would have to understand a lot about the normal population and
what the range of their abilities within that normal population.
And then establish some criteria to define clearly what someone might
think is atypical types of processing, or
atypical ability that might indicate some form of brain damage.
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