cc >> Hi, everyone.
I'm a researcher here at the Waisman Center and a professor
in the Department of Communicative Disorders, and our
lab is the Learning to Talk lab. I'm going to talk about sound
and word learning in children with cochlear implants.
You're going to hear some of the same things that you heard in
some of the other talks. Like Ruth I'm going to start
with the glass half empty or the glass half full, I'm going to
call it good news versus bad news.
Cochlear implants are one of the trials of modern engineering and
single processing. Children with cochlear implants
have much better speech and language skills than we ever
could have imagined looking at children a generation ago with
the same type of hearing impairment who wore hearing
aids. They are mainstreamed, they
speak beautifully, their language is excellent.
We never would have imagined that we would come so far so
fast. We also have to acknowledge that
we're not there yet. Children with cochlear implants
as a group, we know there's a lot of individual variability,
but as a group they don't perform as well as their same
age peers with normal hearing. Speech is slightly less
intelligible. On every measure of academic
achievement, they don't do quite as well.
Here I'm talking also to know that a lot of our kids with
cochlear implants live, like in Lake Woebegone, all children are
above average. We're not content if 100 is the
average score, we're not content that our children with cochlear
implants have scores at the average.
We want them to be above average like all the other children in
their school or town. Of course here we have to think
of what comparison group we're going to use.
We don't want to compare apples to oranges.
It depends who we compare them to.
If we compare children with cochlear implants, if we compare
their speech or language, if we compare them to children of the
same chronological age, they're not going to do as well.
It makes sense to compare them to these kids, they're in the
same classrooms, but it's not fair to compare them to these
kids. For one thing, they've been
hearing for less time. Even if you had a cochlear
implant at age 1, when you go to kindergarten at age 5, you've
been hearing for four years, where everyone else has been
hearing for five years. We could instead compare them to
children of the same hearing age.
We could take kids and say, okay, you're five, but you've
only been hearing for four years, so we're going to see how
you do compared to kids of 4 years.
When we do that, they often do better.
That makes sense. Even if you get your cochlear
implant at age 1, you don't start learning everything at age
1. Maybe you start learning to
speak and learn words, but you've been learning lots of
things from when you were born to age 1.
The difference between the concepts of an apple and orange,
even if you don't know the words apple and orange.
What we often do in our lab is compare them to children with
the same size vocabulary. And when we compare them to
children who have the same vocabulary size we find the most
similarities between children with cochlear implants and
children with normal hearing. The problem is that children
with cochlear implants tend to be on the average of six months
delayed in vocabulary. So they're not quite there.
Now, you know, as people have already said, it's obvious why
we have these differences. You know, the auditory input
isn't as good. 22 channels versus thousands.
So they don't have as good auditory input, and they also
haven't been hearing for as long.
As people have been saying, we have many, many advances in
these areas that are going on even as we speak.
So what we're doing in our -- you know, we're not engineers,
we're not surgeons in my lab. So what we're doing is focusing
on two things. We're trying to understand how
speech and language development is different for children with
cochlear implants as we compare them to children with normal
hearing. This is both in terms of
producing sounds and perceiving sounds.
Also in terms of learning words. And we're also interested in
individual differences in performance.
So if you remember back to Ruth's slides, you can see there
was a huge range of performance in children with cochlear
implants. Some children are really what we
call stars. They perform as well or better
than children with normal hearing.
And what we'd like to do is think of -- try to understand as
well as we can what is going on with this -- with this
variability, so that we can potentially make all children
into stars, all children performing as well as children
with normal hearing. So before I talk about a few of
the things we found, I want to show you this diagram which
talks about the interactions between perceiving speech,
producing speech, and learning words.
So let's start here with speech perception.
This is going to be things like being able to hear the
difference between a ka and a ta, or a and ay, and this is
where we expect children with cochlear implants to have
problems. The auditory implant isn't as
good. And hearing the difference
between ka and ta is really hard.
The problem here is that this interacts with everything else.
So speech perception interacts with speech production.
Being able to make the difference between a ka and ta
or an ah and ay. The better your speech
production is, the better your speech perception will be, and
the better your speech perception is, the better your
speech production will be. We have these interactions, and
the more, the better you get at perception and production, the
better memories you're going to have with these individual
speech sounds. Now if we look up here at words,
you know, having memories for words, you really have two kinds
of memories. You have word meanings.
Obviously we know the difference between something you keep a
bird in and something you eat on a birthday, but when we have a
memory for a word, we don't just have the memory of its meaning,
we also have the memory of its sounds.
We also know that cake is different than cage because one
ends in k, and one ends in ja. The better memories you have no
speech sounds, the better you'll do at learning and remembering
words. We could have this diagram go
even farther up. Up here would be things like
reading and writing, things important for academic
achievement. Because we know that the two I
think that's most important for being a good reader are knowing
lots of words, and being able to break those words down into
sounds. You see this one weak link in
speech perception can lead to problems, difficulties all the
way up. This is what we're interested
in. I can show you a couple results
that we have that show similarities and differences
between children with cochlear implants and children with
normal hearing. So this is from work that a
graduate student did, and what she was interested in was how
children produce sounds. She took the two sounds,
sa and cha, like sip and chip, and she
recorded them from children with cochlear implants, and children
with normal hearing of the same chronological age.
She was measuring the acoustics in the sounds, and one of
the big differences has to do with the frequencies between
the sounds of sa and cha. Sa has a higher frequency
than cha. You see the results here for
children with cochlear implants and children with normal
hearing. This measure of frequency is
along the vertical axis. Sa frequency results are shown
in the white bars, frequencies for cha
are shown in the gray bars. There were all productions that
listeners heard, and said that sounds like a good sound.
You can see for both groups, there's a higher frequency for
sa than for cha, but you can see that the two sounds are much
more distinguished in the children with normal hearing
than the children with cochlear implants.
There's a more robust contrast. There's a bigger contrast
between the two sounds in the children with normal hearing.
Maybe it's things like this, maybe it's these subtle
differences that lead to the speech of children with cochlear
implants being just a little less intelligible.
The other thing that is interesting here, the -- these
black lines are the average, but we've also plotted data for
every individual child in these circles.
You see, first of all, there's lots of variability for both
groups. These are 2 and 3-year-olds.
You can also see there's at least one child with a cochlear
implant who is performing just as well as the best children
with normal hearing. That shows you there are these
stars. That's where we want everyone to
be. In this next slide we're
comparing children with cochlear implants to children who have
the same size vocabulary. And this experiment had to do
with learning novel words. If I said a word you to, this is
actually a word, but it might be an novel word to you,
pulchritude. The first thing you'd have to do
is encode it enough that you could repeat it.
Whether you know this word or not, you would be good as
repeating it. It's like attitude, latitude.
It's not hard to remember and say pulchritude.
This is something we've known no a long time, the larger your
vocabulary the better you can repeat a new word, and that is
something that is very important for word learning.
We did a similar experiment, not with pulchritude, but with made
up words, and we got exactly that result.
We got the receptive vocabulary, how many words they understand
along this axis, how accurate they were in repeating novel
words along this axis. You see for both groups as their
vocabulary increases, they're more accurate.
What is really cool about this slide, we plotted the data for
children with cochlear implants in black.
The data for children with normal hearing in red, and you
see the exact same relationship. Once they get that vocabulary
size they're just as good as repeating novel words.
That's a very exciting result. The a little bit of concern here
is that when we match children for vocabulary size to children
with cochlear implants were on the average about six months
younger. When they get to that vocabulary
size they're functioning, they're learning new words at
least to the point of repeating them in just the same way that
children with normal hearing are.
So that's exciting. This result is for adults.
And this is from work of Matt Wynn, who is in the audience.
His picture is here so you can find him later.
He's a post-doc, who's working with Ruth and me.
This is work he did with other colleagues at the University of
Maryland when he was a graduate student.
He was interested in the same sounds, sa and cha, in
perception of those sounds, and telling them apart both in
adults with normal hearing and adults with cochlear implants.
He gave them two conditions. The listeners heard both male
and female voices, and he gave them two conditions.
He gave them one condition where they saw a female face with a
female voice, and a male face with a male voice, and in the
other condition they just heard the voices, and didn't see the
faces. He found that the adults with
cochlear implants were more sensitive to the visual cues.
They paid more attention to the faces than the adults with
normal hearing. In a way this makes sense.
If the auditory signal isn't as good you should be trying to use
other cues that you might not have to have if you have normal
hearing. So what they were doing, they
were paying attention to a cue that might be in a normal
hearing listener redundant, or was an important cue for a
listener with cochlear implants because the auditory input is
degraded. So with these results, I say the
million dollars question is how can these results inform
clinical progress. I wouldn't say we have a lot of
answers yet, but one thing I think we have to do,
particularly looking at Matt's results is thinking about how we
do auditory verbal therapy. In auditory verbal therapy the
focus is I'm getting the child to pay attention to just what
they're hearing to the extent that we don't even provide them
with facial cues. There certainly are advantages
to that in that we really want kids to concentrate on the
auditory input that they haven't had up to when their cochlear
implant is activated. But it could be that we're
carrying it a bit too far in not also teaching children to
integrate visual cues. Maybe we need to have more than
one condition for children in auditory verbal therapy where
sometimes they're getting the auditory cues only, and
sometimes getting the auditory and the visual cues.
Because we know, we suspect that to be a successful cochlear
implant user, you're going to have to use all the cues that
you have at your disposal, because the auditory input is
degraded. I want to switch gears a little
bit now and talk about another approach that might help all of
our children be stars. And here I want to talk about
something that is a little further away from speech and
word learning, and that is executive function.
Executive function is what psychologists call the cognitive
processes involved in the regulation of three things.
One of these things is working memory.
Working memory is a little different than short-term
memory. Working memory has both stored
space and processing space. And working memory capacity is
limited, as I'm sure we've all experienced.
The example I like to give is how you can drive and talk at
the same time until the driving gets bad.
All of a sudden you're in a lot of traffic or it starts pouring
down rain, and you say to the person sitting next you to, I
can't talk anymore, I have to concentrate on driving.
Cognitive flexibility is being able to switch from one task to
another. Any of you in here with children
know that is something that develops gradually.
That's why we give our children warning about transitions.
Five more minutes, and it's going to be time to get ready
for bed. Inhibitory control is exactly
what it sounds like. It's learning to inhibit our
impulses. Instead of grabbing the last
cookie on the plate, look around at everyone else at the table
saying, does anyone else want that cookie?
We know all these things inhibitory control, flexibility,
and working memory, develop gradually from childhood to
adulthood. What's really interesting about
this is that executive function seems to be involved in speech
perception and in word learning. So in our lab we've seen that
adults who have better executive function, and we can measure
this by standardized tasks, pay more attention to redundant cues
and speech perception. If you take again that example
of sa versus cha, the primary cue in English, the difference
between cha and sa is difference in frequencies.
There's other cues. They're not as important in
English, but they're there. Another important cue is the
frequency at the beginning of the vowel.
What we find is that people who have poor executive function as
measured by tasks tend to pay attention only to that primary
cue, whereas people with better executive function pay attention
to both the primary cue and the secondary cues.
Other people, David Pisoni at Indiana University has shown
that children and adults who have better executive function
measured by standardized tasks or sometimes by questionnaires
are better able to recognize spoken words.
If you ask someone to listen to a passage, and press a button
every time they hear the word cup, people with better
executive function who have cochlear implants will be faster
and more accurate at that task. So this suggests that possibly
teaching -- you know, having people, training people to have
better executive function might result in better outcomes with
cochlear implants in terms of children and possibly adults.
Now what is exciting about that, if you recall, think back to the
original talk that Teresa Palumbo gave, the Center for
Improving Health and Minds, which is right here at the
Waisman Center has developed a preschool program to improve
executive function. It's similar, I don't know if
anyone hear has done as an adult mindfulness stress reduction.
The program is very similar to a mindfulness based stress
reduction program, except it's age appropriate for
preschoolers. It starts with children lying on
their back, and they watch a rock rise and fall on their
stomach as they're taking belly breaths then they're asked
to hold up a finger when they hear a bell stop ringing,
and so on. It's a six week program for
about, I don't know, half an hour a day, and it's been shown
to be effective in improving executive function in
preschoolers and early school age kids.
It'd be really exciting to do such a program with children
with cochlear implants, and see if that does translate into
better speech perception or word learning for those kids.
So I'd like to thank my wonderful collaborators for
their generous support we've had for this research,
and I can take questions. [applause]