ALAN ALDA INTERVIEWS HELEN NEVILLE
Featured on "Old Brain/New Tricks,"
from the Scientific American Frontiers special
"Pieces of Mind."
Alan Alda: I have always assumed
that the brain is hard-wired, that there
are certain parts of the brain that are
dedicated to certain functions, and you
seem to be finding in your work that a
part of the brain that's usually
dedicated to one function, like hearing,
can suddenly shift to seeing. How does
that happen? What's the process?
Helen Neville: Well that's a very
interesting question. You're right. This
is a new discovery made by a handful
of investigators over the past few
years. And that is that these strong
genetic biological biases for the brain
to develop in a particular way can be
changed within limits. There are limits
on the degree to which brain
organization can be changed, but there
is considerable modifiability.
So one of the ways that we think that
an auditory area can be rewired to be
a visual area, for example, one of the
mechanisms that's very likely is that
early on in development, at birth,
many different parts of the brain that
aren't normally interconnected are
connected together. So in a newborn
child, we think, as is the case in
newborn kittens, we think that the eye
projects not just to the visual cortex,
but also to the auditory cortex.
Normally when auditory input comes
in, it competes out the visual inputs, so
that they're sort of kicked out of there.
In the case of a deaf person, there is
no competition from auditory, so visual
inputs can stay there. Now this only
happens if sound input is missing in
the first few years of life.
Alan Alda: It's interesting. It sounds
as though you're saying it's not so
much that vision replaces sounds in
that part of the brain. It's that sound
doesn't get a chance to compete for
that territory, and doesn't overcome
the visual use of that part of the brain.
Helen Neville: That's right. So what
this suggests is that at birth the
human brain is much less
differentiated than it is in the adult.
It's not all neatly divided up into
specialized areas. At birth things are
much more strongly interconnected.
And the final pattern of differentiation,
or specialization, depends on what
experience the child has. It depends on
what sensory inputs come in. Of course
in most cases, a child has both visual
input and auditory input and tactile
input, and that is one of the important
means whereby the brain develops into
these different specialized packages.
Alan Alda: But is there a boundary
here in terms of time? If hearing
doesn't take over by a certain point, is
this change possible later? Suppose
somebody becomes deaf at the age of
fifteen?
Helen Neville: We've observed that
this take-over by visual processing, of
what are normally auditory brain
areas, occurs if hearing is lost within
the first four years of life. And people
who've become deaf later than four,
we don't see this huge visual
enhancement of auditory brain areas.
So at least some aspects of this
modifiability of the brain are limited to
the first few years of life.
Now what we've observed is that
different types of modifications are
more or less likely, and different
effects of experience occur at different
times in development. So that doesn't
mean that it's only during the first four
years of life that all changes can occur.
It's just for the take over of auditory
brain areas for visual processing
appears to be most likely to happen
within the first four years of life.
Alan Alda: Does it work the other way
around too? For instance, somebody
who's blind from birth. Are there areas
of the brain that you would expect to
be dedicated to auditory? Does
somebody who's blind from birth take
over other parts of the brain that you
wouldn't expect?
Helen Neville: Yes. These different
kinds of investigations very recently
have shown increased auditory
responses in the visual brain areas in
people who are blind since birth.
Alan Alda: That's just amazing. That
the brain is kind of malleable, like a
piece of clay in a way. It's not so hard
and fast as at least I thought it was.
Helen Neville: That's right. There's no
doubt about the fact that there are
very strong biases, or likelihoods,
according to which the brain will
develop. That's why in 99.9% of all the
people, this is visual brain, this is
auditory brain, this is the part that's
important for touch, this is the part
that's important for language. But
these strong genetic biases can be
changed, they can be modified, within
limits, within time limits. Moreover,
some kinds of processing are more
malleable than others.
For example, in the visual experiment
we did with you, where we compared
processing visual information
presented to the center versus
information presented to the
periphery, the kind of processing that's
most heightened in the deaf is the
processing of peripheral information.
So we see much, much larger
responses to peripheral visual stimuli
in deaf people than hearing people, but
the processing of information
presented to the center is pretty much
the same.
So some parts of the visual system are
more changeable than others. So this
is very important for us now to
characterize in human development,
what are the kinds of processing that
can be most influenced by education
and other kinds of abilitative
measures? And what kinds of
processing are less malleable? And it's
very important for us to determine
when in human development changes
can be made, and what are the time
periods beyond which changes are
much more difficult to make.
Alan Alda: What about the next test I
did, with the recognizing sentences?
What were you observing during that
test?
Helen Neville: Well, what we
observed in you, as we do in most of
our hearing, speaking individuals, is
that when you process English, we see
a lot of activation within the left
hemisphere, less activation in the right
hemisphere. So there's this big
asymmetry in the way our brain is
organized for language. At least the
brain of human speaking people.
So there appears to be a strong bias
for the left hemisphere, for particular
regions in the left hemisphere, to
process language information. Actually
this asymmetry between the two sides
of the brain in processing appears to
be much more pronounced for
processing the grammar of language
than for processing vocabulary and
meaning and semantics.
Alan Alda: Much more pronounced in
what way?
Helen Neville: We see very
asymmetrical responses, that is much
larger left than right hemisphere
activations, when you process
grammatical information in sentences.
Alan Alda: What would be an
example?
Helen Neville: Well, like the words in
the sentences that gave you
information about who did what to
whom, like the words and, the, but,
although, and heretofore - those little
words that carry a lot of grammatical
information in English.
Alan Alda: So there's a part of the
brain that tends to be used more
frequently for words like that? And
what part of the brain is that?
Helen Neville: Toward the front in the
left hemisphere.
Alan Alda: Whereas the other words
are being worked on where, oh in the
back.
Helen Neville: Toward the end of that
temporal lobe.
Alan Alda: That's interesting. So does
that mean if somebody got an injury to
the brain in that region, and they were
a speaking, hearing person, that they
would tend to lose their sense of
grammar, but they'd retain the rest of
their vocabulary?
Helen Neville: Yes, there are huge
differences in the effects of lesions to
these more frontal and posterior areas
of the left hemisphere. Typically
patients with lesions to this region of
the brain have great difficulty
producing those little words, and have
great difficulty telling the meaning of a
sentence if it depends on the word
order or the grammatical construction.
But they know the meaning of words.
They know vocabulary items.
So it looks as though really different
brain systems are used for processing
different parts of language. And this is
a question that we ask in our research,
parallel to the questions that we've
been studying in vision. And that is:
are these different language systems
of the brain also more or less
modifiable by early language
experience? Just as in the case of
vision, some parts of visual processing
are more changeable than others.
Alan Alda: How limited are you by the
age of which you learn a language?
What are your limits? Let's say, in my
case I started studying French in my
teens. I got really serious about it in
my late teens, and I thought I could
speak pretty well. What were the
things limiting me?
Helen Neville: We've observed, and
others have observed as well, that
sounds and grammar are the parts of
the language that suffer most from
delayed learning of a language. So you
probably speak with an accent in
French. People will probably tell you
that. And your grammar probably isn't
perfect. On the other hand, you
probably have a huge vocabulary. Is
that true?
Alan Alda: Yeah, I think that's a good
description of it. I speak with a pretty
good accent in French when I work on
it, but it would be difficult to pass
myself off as a French person. There
are certain things that I think I'm
saying right. Then when I hear a
French person say them, I realize that
there's a difference.
Helen Neville: Well there are, of
course, individual differences in the
ability to learn a second language
without an accent. But for the most
part, you can tell when a person
learned a language by whether they
have an accent or not.
Alan Alda: If there is this plasticity,
this malleability of the brain, how
come it doesn't persist? Why does it
close down? Are there things you can
do to maintain that flexibility in the
brain?
Helen Neville: Some aspects of
processing remain plastic throughout
life. This is an important sort of
breakthrough that a number of
neuroscientists have made over the
past ten years. So, for example, the
learning of a vocabulary can be done,
you can always learn the meanings of
new words, throughout your life. As it
turns out, the representation of your
fingers in the brain also changes
throughout life. So if you learn a task
that involves excessive stimulation of
these two fingers, these two fingers
will develop a much larger
representation in the brain, even if this
happens in adulthood. So some aspects
of learning retain this plasticity
throughout life. Even in adults.
Alan Alda: So it's not a waste of my
time to keep trying to get better at
tennis, for instance.
Helen Neville: Absolutely not.
Alan Alda: Cause some parts of my
body are liable to cause bigger areas of
my brain to get hip to all this stuff I'm
trying to do. But somehow, parts of
language - grammar and pronunciation
- are more limited. Now why would
that be? Does that any of your work
throw light on why that should be the
case?
Helen Neville: I think this is one of
the biggest conundrums that
neuroscientists are faced with today,
and that is - well, first we must
characterize which systems are
changeable and which aren't. I've
given you two examples of systems
that are more or less changeable, and
those that are less changeable. At the
present time we don't have enough
information that would enable us to
say what the invariance is. Why are
some systems changeable throughout
life and others not?
Alan Alda: Is there anything in your
work that gives you a clue, a hint? Is
there some field of inquiry you're
pursuing to see if you can figure out
why the brain just sort of gives up on
grammar after a certain age?
Helen Neville: Why some parts of the
brain don't maintain their plasticity?
You know, the flip side of plasticity is
vulnerability too. So the more that a
system is modifiable by incoming
experience, means the more
vulnerable it is to incoming experience
as well. So it could be that aspects of
processing that are dependent on early
experience stop. This is something I've
been asking my fellow colleagues for
about the last three months. Why are
some of these systems more
changeable than others?
Alan Alda: Well, what do you want to
know about how workable the brain is?
Helen Neville: The first thing we need
to do is to characterize the degree to
which different systems are modifiable
or not modifiable when their windows
of opportunity or critical periods are.
Right now we have very limited
information about this, especially in
the human. We have some information
within the visual system, some
information in the language system.
We need to know more. And once we
characterize the plasticity and
modifiability of a number of different
systems, then we might be able to see
an invariance in those systems that
are modifiable throughout life, and
those that aren't.
For example, it may be that systems
that are modifiable throughout life
have more redundant connections at
birth, and retain those redundant
connections throughout life. Whereas
the systems that are more constrained
in their modifiability have fewer
redundant connections early on.
Alan Alda: That was a good example,
except it's hard to follow. Just go over
that ground again. One of the things
you'd like to know about is whether or
not these parts of the brain that can
change, can change because there's
something about them that's different
from other parts of the brain?
Helen Neville: Right.
Alan Alda: And what is that?
Helen Neville: For example, they
might be more strongly interconnected
to more brain areas.
Alan Alda: Oh, just more connections.
Helen Neville: More connections. So
for example, if this finger is normally
actively connected to a certain part of
the brain. But it could be, it seems
very likely, that it's also connected to
adjacent parts of the brain. So that
with increased training, this finger now
takes over all these neurons.
Alan Alda: But maybe it wouldn't be
able to if it didn't already have those
connections to other parts of the brain.
Helen Neville: That's right.
Alan Alda: So one of the things you
want to look for is to see if those parts
of the brain that don't change much
after a certain period of time, like the
grammar parts of the brain, you want
to find out if that's because they don't
start out with enough connections to
other parts of the brain?
Helen Neville: Yes. They have less
redundancy. Greater specificity.
Alan Alda: So how would you find that
out? Are there tests you're doing now
going to help you see whether or not
that's the case?
Helen Neville: Yes. That's one of the
reasons why we study young infants
and young children. To compare brain
organization in the immature brain and
the mature brain. And actually we
have observed that in young infants, at
birth and at six months of age, that
visual responses elicit large potentials
over both visual and auditory cortex,
suggesting the brain is much less
differentiated at birth than it is in an
adult. And now, we're just conducting
experiments to see whether that lack
of differentiation is more apparent for
the central part of vision than for the
peripheral part of vision. So these
experiments that are underway right
now.
Another factor that's likely to be
important in the relative plasticity and
modifiability of different systems is the
rate at which they develop in normal
development. So it could be that
systems that develop over a long time
course retain their plasticity over that
developmental time period, but after
things are set in place, then the
plasticity just shuts down.
ALAN ALDA INTERVIEWS HELEN
NEVILLE
PAGE 2 OF 2
Alan Alda: Is that something you find
true in other ways of looking at the
brain, that if it takes a long time to
develop, it tends to be malleable
during the time, and if it takes a short
time it's not?
Helen Neville: Absolutely. So for
example, the time period when surgical
intervention can lead to corrected
vision, say in the case of a wandering
eye. That time period when the
surgery is effective is probably two to
three years of age in a human. But we
know that the time when language can
be learned, using different parts of the
brain, is much longer. At least the first
ten years of life. We know that by
studies of children who've had to have
the entire left hemisphere removed. In
such cases, these children can learn
language perfectly well, if the surgery
is done before the age of ten. So this
shows there's a much longer period of
plasticity for language processing than
say for visual processing.
Alan Alda: What about that third test
you gave me, where I was looking at
sign language? First of all, what were
you seeing in my brain when I was
trying to interpret that? Cause I don't
speak American sign language.
Helen Neville: So your brain
responses to the sign language did not
show the typical activation patterns
over the classical language areas of
the left hemisphere, that we saw when
you were processing English.
Alan Alda: So in other words, I was
looking at the language, but it didn't
have meaning for me, so it wasn't
registering in the same place as when I
look at a meaningful sentence.
Helen Neville: Exactly right. We didn't
see activation of the classical language
areas.
Alan Alda: Why is that useful to you?
Helen Neville: Because you serve an
important control for us. Because we
did the same experiment with our deaf
subjects, of course. And we asked, if
you learn a language which is not
spoken, and not oral or aural, but
instead is sign language - and sign
language, as you know, makes
extensive use of visual space, and
importantly depends on the perception
of motion. Now remember, the
perception of space and the perception
of motion in normal hearing people is
dependent on the right side of the
brain. But language in normal hearing
people is dependent on the left side of
the brain.
Alan Alda: So what happens? What do
you see in their brain when they're
looking at meaningful speech?
Helen Neville: So that's why that's
right. That's why we ran that
experiment. And what we observe is
that the same classical language areas
in the left hemisphere are active when
deaf people process sign language.
Even though it's visual and spatial, and
involves a lot of motion perception, we
still see activation of the classical
language areas of the left hemisphere.
Alan Alda: Now when you were
looking at me, looking at the sign
language, you saw no special activity
in the language area, on the left side
of my brain. Did you see a lot of stuff
on the right side of my brain, where I'd
process motion and space?
Helen Neville: Yes.
Alan Alda: And do you also see that
as deaf people look at signing?
Helen Neville: Yes we do. That's
exactly right. We see activation in you,
primarily of right hemisphere areas. In
deaf subjects we see activation of
classical language areas, and activation
of areas within the right hemisphere.
And we think that this makes two
important points. One is that there's a
strong biological bias for these regions
of the left hemisphere to process
language. Whether it's spoken or
signed. So that's a bias, in the way
that the language areas of the brain
will develop.
But the fact that we see such robust
activation within the right hemisphere
at the same time suggests that if you
learn a language that depends on the
perception of space and motion, you
will also recruit other areas into your
language system. Namely areas of the
right hemisphere that are important
for the perception of motion and space.
So this shows there are biological
constraints on the organization of the
language systems of the brain, but also
that early experience plays a very
critical role in determining the final
pattern of brain organization for
language.
Alan Alda: What else does it tell you?
I'm just so impressed that you have
really opened up a window into the
brain, and found things that you
probably didn't expect to see. What do
you think about when you look into the
brain, and you see things going on that
are unexpected like this? It must, at
least in the back of your head, make
you want to shine a light in other parts
of the brain and learn other things.
Helen Neville: It makes me think
about how this highly differentiated
mosaic of cortical systems that we see
in every adult that we study, how it
comes about. Now we know that it
comes about very slowly, it comes
about in stages that are different for
each different aspect of information
processing that goes on in the human
brain. And what this means is we need
to further characterize all the different
stages of brain development. And the
time periods, when brain development
critically needs specific kinds of inputs
from the environment, and without
which the brain will not develop
normally.
So, for example, we've observed in
people who are exposed to language
very late, later than normal, as in the
case of deaf people who don't learn
sign language early on and basically
are without language, until they, say,
go to a residential school for the deaf,
we see that this lack of language input
during the first few years of life can
have very deleterious effects on brain
organization, and lasting effects on
brain organization.
So what this makes us aware of is the
fact that certain kinds of inputs are
necessary if the brain is going to
develop optimally, and that different
kinds of input from the environment,
provided by education or provided by
habilitative regimes, would be
optimized by determining exactly when
they are most effective in human
development.
Alan Alda: Has this given you a
different way to think about education?
Are there things we should be doing
sooner when we educate children?
Helen Neville: I think that once the
data are all in, and we do experiments,
for example, in the learning of music,
the learning of math. All of these
experiments remain to be done. We
don't know when the critical time
windows are. When learning math,
learning music, learning science,
different kinds of learning, would be
optimized. But I don't have any doubt
that there are such critical windows of
opportunity. We just need to do the
research to determine when they are.
What we do know is that from the
point of view of language learning,
early is better. Children need to be
exposed to a language, a proper formal
language, with a grammar, early on if
they are ever to have optimal
language skills.
What this means is that, for example,
second language education shouldn't
be saved until high school. It should be
begun in elementary school. Children
who are born deaf should be exposed
to a proper formal language early,
rather than later. I think is very clear
from the work that's been done so far.
Alan Alda: Now that sounds like
you're saying that if hearing people
have a deaf child, and they don't know
how to sign, but just keep hoping that
the child will pick up some spoken
English, that that child is really not
getting a fair shake. Because the child
is not being exposed to a fully
grammatical language, as they would if
they got ASL from the beginning.
Presumably they can't speak from the
beginning without a great deal of
difficulty. Are you speaking in favor of
ASL or early learning?
Helen Neville: I'm definitely in favor
of giving the child a language, a formal
language, as early as possible. Most
profoundly deaf children, who are born
deaf, cannot learn a spoken language,
because they can't hear it. So exposing
these children to sign language would
give them a language initially, and
then they could use that sign language
to learn English later. But it's very
difficult if you don't have any hearing
to learn a spoken language. So
exposure to sign language early on
would definitely be important in the
case of a profoundly deaf child.
Alan Alda: I think it's possible that
parents are afraid if they teach a child
ASL and then try to teach them
English, that they may not get good
spoken English. That there's some
interference. I think a lot of people are
afraid if you teach a child two
languages at the same time, or almost
at the same time, that they interfere
with each other, and they won't learn
either properly. Have you found that to
be true?
Helen Neville: Well, research by
many different investigators, actually,
has shown that children can learn two,
three, even four languages without
lasting interference effect and with
great facility. So children are language
learners, much more so than adults.
They learn language easily and
effortlessly, whereas for adults it
requires a great deal of effort. So it
certainly doesn't hinder the acquisition
of language to learn a different
language early on. It certainly does
hinder language acquisition if you
delay it. That's been shown amply by
many different techniques. Behavioral
studies as well as brain imaging studies
like ours.
Alan Alda: Does learning to read
become a part of this? I've wondered
sometimes, in my eagerness to teach
my grandchildren to read as early
possible, I wondered if rushing them
with that is not a good idea. Do you
include reading along with language,
when you speak about learning early?
Helen Neville: Actually that's a really
interesting question that we don't
know very much about. We don't know
very much about the effects of learning
to read on brain organization. So when
we've been talking about language
acquisition just now, I'm talking about
natural acquisition of either oral, aural
language or sign language. Not
reading.
It's interesting, because reading is
typically learned pretty late by
children, six or seven. That's much
later than one or two. And with a great
deal of effort. It's difficult to learn to
read. And certainly children are ready
to learn to read at different times in
development, so there wouldn't appear
to be any point at all in rushing a child
in reading.
Actually, many studies over the past
few years have shown that children
who learn ASL outperform other deaf
children in terms of their scores in
math, scores on English, scores on
everything. Their performance at
school, and by every sort of
standardized measure that's been used
in the schools, kids who learn ASL out
perform kids that don't learn ASL. So it
certainly doesn't hinder the acquisition
of English or the acquisition of
anything else.
Alan Alda: What about hearing
children, who have no reason to learn
ASL, but that it's interesting, it's
challenging, it's fun, or they may have
somebody in the family with whom
they want to communicate, but they
personally don't need to communicate
through ASL for the most part. Do they
have any advantage in learning ASL in
addition to their regular spoken
English?
Helen Neville: I don't know of any
studies that have addressed that
question. That's an interesting
question.
Alan Alda: I wonder if there's
something about ASL that just makes
you smarter.
Helen Neville: Well, that's possible,
but my own feeling is that the results
of the studies are due to the fact that
having a language is better than not
having a language. So those kids who
learn ASL early have a language. They
can use that language to learn
geography, to learn math, to learn
English, but if you don't have a
language it's very difficult to be taught
anything.
Alan Alda: When you study young
children here in your lab, what are you
looking for, what are you learning
about those children?
Helen Neville: Well, we want to know
more about why the adult the brain is
highly differentiated. This part's for
vision, this part's for hearing, and so
forth. We want to know how this comes
about. For example, for a long time
people thought that most aspects of
brain organization were present at or
before birth, and were basically
genetically determined. Of course,
instead what we see is that this
pattern of organization arises over a
very protracted period of time after
birth. Some parts of the brain are
mature, look mature, much earlier
than others. So for example, visual
cortex basically looks mature by about
four or five years of age. But if you
look at the maturation of temporal
brain regions, frontal brain regions,
these areas don't look mature until the
late teens.
The most astonishing, little known fact
is that by just about any anatomical or
physiological parameter that's been
investigated in the human brain, the
human brain doesn't look fully mature
until at least fifteen or twenty years
after birth.
Alan Alda: I thought you were going
to say sixty, sixty-five.
Helen Neville: There are no
guarantees of maturity, of course.
What this suggests is there's a very
long time period when the brain is
getting itself organized. What this
means is there's a long time period
when input from the environment
could affect the ultimate pattern of
brain organization.
Alan Alda: And what does it mean for
a child that doesn't get guidance,
input, some kind of mentoring, during
all those crucial years? What kind of a
child do you produce? What kind of an
adult comes out of that?
Helen Neville: See, that's the flip side
of plasticity. That's exactly right. The
flip side of plasticity is vulnerability.
The brain is very vulnerable. It's
waiting for certain kinds of inputs. And
if those inputs don't occur, then brain
development won't occur in a natural
optimal fashion. So this means that
children who don't receive language
input during the time when the brain is
waiting for language input will never
develop optimal language skills, and
the normal brain organization for
language.
Children who don't get appropriate
visual input during a certain time
period will never develop, for example,
appropriate depth perception. This puts
the onus on parents and educators and
habilitators of children with
developmental disabilities to determine
when the time periods are, when
particular kinds of inputs are necessary
for optimal brain development.
Alan Alda: What are some of those
things that you are pretty sure you
know now? What are some of those
abilities that need to be developed
before it's too late, and when is it too
late for them? You talked about depth
perception. What else is there?
Helen Neville: The point that I want
to make the most strongly is that we
know very little about human brain
development at the present time. We
need much more research. We
certainly know that convergent input
to the two eyes is necessary in the first
two to three years of life.
Alan Alda: That's depth perception.
Helen Neville: In order for normal
depth perception to develop. We know
that different inputs to the two ears
are necessary in order for optimal
sound localization to occur. And these
two different inputs need to occur
within the first eight years of life. We
know that exposure to the sounds of a
language, and to the grammar of a
language, should occur at least before
the age of eight to ten, if a
phonological and grammatical
processing is to proceed normally.
Those are some of the things we know
about human brain development, and
it's very likely that there are similar
constraints on other aspects of
development, but systematic scientific
research hasn't been done on these
issues yet. For example it's very likely
that exposure to musical education and
learning to play an instrument is going
to occur better sometimes than other
times.
Alan Alda: The sense of pitch,
wouldn't that be affected by early
training?
Helen Neville: Well, it's very likely,
but systematic studies haven't been
done. So this is really a call for
research.
Alan Alda: The whole notion of being
tone deaf, it would be interesting to
find out whether or not one has
something that's just inborn, that's a
problem, or that there wasn't enough
of the right kind of stimulation at the
right time. Maybe a whole range of
things like that.
Helen Neville: That's right. The whole
discussion that we've been having
would suggest that we should try not
to think in terms of either/or. Either
it's genetically determined, or it's
dependent on early experience. So
what we know is that there's a lot
about the brain and behavioral
development that's strongly biased, but
that even to express those genes,
certain kinds of inputs is necessary. So
there's a strong bias for this part of the
brain to process sound information.
But if there's no sound information
that comes in, obviously it won't be an
auditory brain area, and in fact it come
become a visual brain area, or a touch
brain area. So instead of thinking
about nature versus nurture, we know
that they're intricately interwoven.
Alan Alda: You know, it's very
interesting, this discussion of what
dominates in us, nature or nurture.
This is a very old discussion, and it's
usually resolved by somebody saying,
"Well, they're intertwined." But you're
describing something that I don't think
I've ever heard before. The idea that
nature itself, the hard-wiring of the
brain, changes by virtue of the cultural
input at the right time. The right input
at the right time. That's an interesting
notion. And you're even finding out
when it has to be done, and exactly
what has to be done. And the very
nature that we come out with is
different as a result of that. And our
genetic inheritance isn't over,
apparently, when we're born. It's still
in the works.