Ellen Bialystok [ University of Reading ] I’m going to be talking about my research that shows how a very ordinary experience — bilingualism — has the ability to change and improve cognitive function across the lifespan and even delay symptoms of dementia in older age.
Thank you so much for this incredible honor. It’s tremendous to be here and I want to thank everyone who’s responsible for this in the School of Psychology and Clinical Language Studies and in particular Professor Rothman who invited me and has organized all this. Thank you very much.
The main concept that I’m going to talk about today is neuroplasticity. This is the idea that our brains and our minds change as a function of what we do with them.
Fifty years ago that would have been a shocking statement but now it’s perfectly accepted that we change from our experience.
I’m going to show you some examples.
A study fifteen years ago showed that London taxi drivers , who had to memorize the streets of London in order to obtain a taxi drivers license, had enlarged portions of the brain region responsible for spatial navigation .
This is a well-known finding now in psychology. The posterior hippocampus of taxi drivers is larger than non taxi drivers — but it’s actually more complex than that.
Another theme of my lecture is going to be, “nothing is simple”. Everything has to be looked at from multiple angles.
So if you actually look at the data you will see that in the back of the hippocampus the taxi drivers indeed have larger volume.
But what nobody talks about is that the front of that same structure shows the opposite.
It’s not that simple
A second example comes from clinical intervention for stroke.
Let’s suppose you have a stroke in the right part of your brain that paralyzes your left arm.
Typically therapy would be aimed at strengthening the right side so that it compensates.
What he does is take the good arm, immobilizes it, and waits for the brain to forge new pathways so that the left arm — which had been paralyzed — is now functional.
Now she can use her left arm but not through the old pathways.
The brain has rewired.
This is neuroplasticity.
Finally, we’ve known for a long time — we figured this out in the 1940s — that the kind of environment you’re in modifies the kind of cognition you develop.
Edward Taub showed that rats who were raised in more interesting cages, with the opportunity for stimulating activity — as opposed to standard lab rat cages — these rats were smarter (in rat terms).
So we’ve known that for a long time, and this has been replicated many many times, but the surprising new extension is that that enhancement in cognition — from being in a stimulating environment — can get passed on to the next generation .
So the offspring of the rats who were raised in the Disney-like cages are also enhanced — even though they have never been in those cages themselves. .
So we’ll just use this graph.
This is the offspring of the rats whose mothers were raised in stimulating cages, whose fathers were raised in stimulating cages, or who were raised in ordinary lab rat cages.
This is how much interest they show — an exploratory behavior which is a sign of rat intelligence — and you can see these are highly significant differences.
So these changes in brain structure and function get transmitted.
How do they get transmitted?
Possibly through DNA methylation — but that’s another story.
So what we can see is that experience changes brains and behavior — but these effects are complex.
They are not linear and they are certainly not one-to-one relationships.
To sum up : neuroplasticity is the idea that the experiences we have change the shape of our mind and brain.
To give you a different way of thinking about this, consider a beach that has an expanse of damp sand. Think of that as the brain — and then creatures and people walk across the beach and leave their footprint. So the substrate of the beach carries the indelible mark of the act that someone or something has walked across it.
That’s the way brains change to reflect structure.
Think now instead about something like cross-country ski tracks through the snow.
The more times you ski through those tracks the faster those tracks become.
Experience is making that pathway more efficient — faster — and that’s a metaphor for what happens in the mind.
Something that you do often, in a particular way, becomes easier to do and reflects precisely your experience in doing it that way.
Now there are many experiences that are well accepted to have the consequence of change in mind and brain in these ways.
For example, formal education is well known to improve cognitive function and possibly brain structure.
Musical training: a number of studies show that this also benefits cognitive performance through neuroplasticity.
The experience that seems to have the largest impact is actually aerobic exercise. Just bringing blood — I know I hate aerobic exercise, really it kills me to say this, but the evidence is really good. The experience of of having these sort of oxygenation experiences in your brain improves the structure and function of your brain.
So why would I want to put Bilingualism on this list of all human experience.
I don’t think there’s anything as intense as the way we interact with language.
If you’re a professional musician you may practice three or four hours a day — but if you’re a human you’re using language every second you’re awake.
In some way it’s also democratically distributed — by that I mean you don’t need to have special talent.
You don’t need to have special privilege.
There isn’t an ability barrier that prevents some people from accessing language — it’s available to everybody — and, as such, the particular language experience we’re talking about — bilingualism — comes as close as you can to the gold standard of random clinical trial.
People are randomly assigned to be monolingual or bilingual, by and large, by virtue of where they’re born, who their parents were, what they’ve ended up doing with their lives.
You don’t need to apply for a permit.
And finally, of all the things we do with our brains, language touches the most centers.
There’s this cartoon idea that language processing takes place in this little bit on the left in the middle.
But, in fact, if you look at an image of someone doing any kind of language processing, it involves the entire brain.
So, if any experience is going to have the potential to create neuroplastic changes in our mind, brain bilingualism should be a high candidate.
On this slide, I’m going to show you the whole story.
In one slide, and all the rest, is commentary.
Here is what goes on in bilingual minds.
In your mind, you have some kind of abstract representation of language and if you’re bilingual you have two.
The key to the whole story is that both languages are always active to some degree.
There is no language switch that is the key.
You think if you wanted to build a bilingual robot you’d have two compartments and a toggle switch — but that’s not how our minds are built.
Both languages are always active to some degree.
So why is there no confusion?
Why do you get the right language out in the right context most of the time?
The reason is because there is another set of processes in the brain — at the front — called the executive function system, or executive control processes, whose job it is to selectively attend to what you need to be doing. When you’re driving rapidly down the highway, and you’re looking for an exit, and you’ve got to watch the instruments on your car — and the traffic around you — and read the signs.
You have to pay a lot of attention to a lot of rapidly changing information.
The way you do that is by the executive control system tuning you in to what’s important — right now — for safe driving.
So the story is that the brain is sitting there, there’s two languages active — oh my god which one am I going to use? — the executive control system jumps in to to solve the conflict and direct attention to the target language.
Because that’s what it does.
As a function of doing this all the time that executive control system is changed — that’s the beach with the footprints and the cross-country ski tracks.
It’s used all the time for this unusual task and it changes as a result of it.
How does it change?
What are these changes I’m talking about?
One which might sound a little counter-intuitive is that language processing becomes more effortful — that is, for bilinguals it’s harder to use language.
Another manifestation, and I’ll come back to this in a minute, is that on average bilinguals have a smaller vocabulary in each language than a monolingual speaker of that language.
Not a smaller vocabulary overall — but of each language.
However, in contrast, their executive control system is enhanced.
I have to say that, of all the things — of all the cognitive processes that our mind has available, the executive control system is the most important by far .
It’s also the most expensive system that we have — in that it takes a long time to develop through childhood.
It’s not really fully functioning until late adolescence and it starts to decline quite early in adulthood.
In middle age it’s already showing deterioration.
So it’s a very highly valued system — and it’s expensive in that it’s very restricted.
We get improved — more effortful — language processing, better executive control processing, and we find these changes both in brain and in behavior.
However, as I said a minute ago, nothing is straightforward.
So these consequences are not linear .
They’re not one-to-one and they’re not categorical.
So you have to search some time to see what’s going on and, crucially, they interact.
Let’s look for a minute at these linguistic consequences of bilingualism .
I said that monolinguals tend to have a larger vocabulary than bilinguals in each language and here are just some graphs to show you.
These are data from about 1,700 children and 1,600 adults .
These are scores on a standardized vocabulary test — where 100 is the population average. The blue lines are the bilingual distributions and the red lines are the monolingual distributions.
What you can see first is that these distributions are quite normal-looking.
That kind of bell shape is exactly what you’d expect of any trait distributed in a popular relation.
But what you can also see is that, in these two groups, the monolingual normal curve is shifted slightly to the higher end and the bilingual curve is shifted slightly to the lower end.
Now that difference is highly significant — so you’d say monolinguals have a higher vocabulary than bilinguals — but what does it really mean?
All of these points, that would come between this red line and this blue line, could belong to either monolinguals or bilinguals.
But on average, monolinguals know more words in each language — both for children and adults.
Another consequence is that it takes longer for bilinguals to retrieve individual words — and by longer I mean milliseconds longer.
So in ordinary speech, in trying to retrieve a specific word for a specific concept, it takes bilinguals measurably longer again on average.
[PENDING DEGARBLING: There are data from Tom our goal on.]
What people are doing in this study is naming pictures — seeing pictures of very common things and just saying what it is.
The blue lines are bilinguals.
All my graphs will have bilinguals in blue.
This is how long it takes.
So the bilinguals with a higher line are taking longer.
Here they see this set of pictures, then they see exactly the same pictures again and again and again and again — so you get faster, because they’re the same pictures.
But right up till the end it’s still slower for bilinguals.
It takes longer to retrieve individual words and one of the reasons might be because, for bilinguals, they have to deal with this conflict.
They have two choices every time they want to name something. Selecting the label that’s appropriate for this experiment, for this task, can account for at least some of those extra milliseconds.
All of this together means using multiple languages is more effortful.
Let’s turn now to what I call the Executive Control Advantage s.
We’ve shown these at all ages and we show these largely with simple tasks that present conflict.
I’ll show you one or two examples so you see conflict that has to be resolved in order to make a fast and accurate response to some kind of visual display.
What we see basically, in this research, is that bilinguals do these tasks better — which is to say they’re faster and sometimes more accurate and crucially they do these tasks — they perform these tasks — using different brain networks .
So they don’t even do it the same way.
Think about the patient that had learned to use her right hand but through different pathways.
I’m going to show you an example:
The Simon Task is one of the very simple perceptual tasks that’s often used in this research.
I’m going to show you first the task.
You are told that you’re going to see a red square or a green square on the computer screen.
If you see a red square, press the button on the left.
If you see a green square, press the button on the right.
But the squares appear on the side positions of the screen. So if it’s a red square, on the left, that’s easy. And if it’s a green square, on the right, that’s hard.
The reason it’s hard is because we are hardwired — from the days when we were on the lookout for woolly mammoths and things, and we were hanging in trees — we are hardwired to respond to movement in periphery.
So a flash of light or motion in a peripheral vision will draw your attention and you can’t help it.
That’s how you’re wired.
So in this task, on the incongruent trials, you’re drawn to one side. But you have to override that in order to press the correct button and that takes time.
The amount of time it takes is called the Simon Effect and the way you do it is by the front part of your brain saying, “not there stupid, it’s the right”.
Now I’m going to show you the data we did.
These data were published ten years ago.
What we did is take the same simple task and give it to people at different ages.
First we go to children — and I think they were about seven or eight or something — and here’s the result.
These are the reaction times for congruent trials and incongruent trials
These are reaction times.
Higher means worse performance.
Those are monolingual children and bilingual children.
Then we took the same task and gave it to young adults — basically Psych 100 students who have to be in experiments — and those are the results.
Absolutely no difference. Absolutely no difference between them.
But notice how fast they are .
They are really fast — and they’re not making mistakes .
Then we went to middle aged adults with the same task and now what’s happening is the middle-aged monolinguals are starting to slow down a bit — in particular on the harder trials — but the middle-aged bilinguals are still doing pretty well.
And finally we went to older adults — and again you can see the monolinguals are slower and the bilinguals have slowed down substantially but they’re still better.
So something different is happening at these different stages of life and it appears that at one stage — 20 year-olds — it appears that nothing is happening at all
But you have to look at the whole context and the pattern of these results across the lifespan.
So what have we got so far?
The constant use of two languages is beneficial for executive control but makes linguistic processing more effortful.
But that sounds too simple too — doesn’t it?
Because we know that language processing often requires executive control.
Here we have a case where the distinction is looking too categorical.
What happens then — when language processing includes the need for executive control — is that going to help bilinguals who have better executive control but overall words language processing?
I’m going to show you a set of studies where we examine this question using a standard neuropsychological measure called verbal fluency.
This is a very ordinary task.
If you fall off your bicycle — fall off your motorcycle, bash your head and go to Emergency — to see how you’re doing somebody will give you a verbal fluency task because it’s a really simple test that gives you an enormous amount of information about brain function.
The test comes in two conditions and each one is designed to test something slightly different.
The first one is called Category Fluency or Semantic Fluency.
There’s different names and it’s this: You have 60 seconds and I want you to name all the animals you can think of or all the fruits you can think of or all the pieces of furniture you can think of.
It’s essentially a test of vocabulary knowledge — especially because your Semantic Memory (where all these words are stored or organized), once you say dog, once you think about a thing. Once you have cat you can think lion.
So it’s really supported by the organization of semantic memory.
And we know which part of the brain is used when you’re performing this task — it’s essentially the part of your brain that’s involved in Semantic Memory.
The second condition is called Letter Fluency or Phonological Fluency or Phonemic Fluency and the task is: ok now I want you to generate all the words you can.
Let’s start with the letter F. That’s a lot harder because there is no conceptual structure in your mind that’s organized around orthography. You’re also given restrictions so that you can’t use variations of the same word.
So if you say fall, you can’t say falling, fell, felled — you can only give one version.
So it’s a much harder task and it requires vocabulary, of course, but a big dose of executive control.
So these two conditions compare two different aspects of verbal processing.
One that does and one that does not also involve executive control.
Okay so here’s the predictions.
Let’s say you have some kind of standard performance, and some kind of standard monolingual and bilingual, and you give them a category fluency task that assesses vocabulary.
Alright so I told you that bilinguals have a smaller vocabulary on average, so we expect bilinguals to do more poorly and now we’re going to give them a Letter Fluency Task that assesses both vocabulary and executive control.
The bilinguals have a control advantage.
What they should do is come back up to compensate for their lower vocabulary — that’s the prediction.
Here’s the data — we’ve done this a few times.
For Category Fluency monolinguals are producing significantly more words than bilinguals and for Letter Fluency there’s no difference.
I’ve stressed that these vocabulary relationships are averages. It doesn’t mean that every monolingual has a higher vocabulary than every bilinguists — for whom vocabulary has been controlled.
We’re going to choose people who have the same score on a vocabulary test.
The predictions are that, for Category Fluency, there is no deficit.
Bilinguals should perform the same as monolinguals.
And now when we add in Letter Fluency, the bilinguals still have that advantage.
So now they should outperform monolinguals, if that’s what’s happening in these tasks.
Here’s the data — the blue and the red lines are the ones I showed you before — I’ve added on the pale blue lines, which are bilinguals who were selected to match monolingual zhan [pinyin!] vocabulary.
Not surprisingly, the bilinguals here perform.
I get the same score as monolingual x on Category Fluency but they significantly outperform everyone else on Letter Fluency.
When you add together a task that requires linguistic ability and executive control — now it’s more complicated. It depends what the task is.
We did this with children and young adults and older adults.
This is just to show you that these patterns are the same across the lifespan.
We can show this dissociation in performance, on this very specific linguistic task, as a function of how what their vocabulary is and the possibility of bilingualism improves scores on the Letter Tasks.
So what we see from this is that these processes of word retrieval are different for monolinguals and bilinguals. There are complex relationships between linguistic and cognitive processes.
I started by telling you that this is a very standard neuropsychological test that’s given to everybody who comes in to an Emergency Room with a concussion.
If it’s really true that bilinguals perform these tasks in a different way to a different level, then attention must be paid to the standardized norms that are used, in these tasks, to evaluate the performance of the patient.
One quick further example, before I move on, where again I want to show you that there isn’t a dichotomy between Linguistic Processing and Executive Control.
So it goes like this:
I’m going to give you a list of words
I’m going to give you all these words then, after a period of time, I’m going to say either, “okay tell me back all those all the words you heard” or I’ll show you words that have a bunch of words you didn’t see and you just say yes or no.
The crucial word is this leak did I say sleep? Was sleep in the list? No. But there’s a tremendous pull to believe that you saw sleep because it’s associated.
How do you prevent your brain from wildly associating when you don’t want it to?
We thought this would be interesting because it’s a little bit like what happens with bilinguals who are wildly associating to the same word in the other language and they have to keep it out.
They might be good at this because a word that’s activated and associated, but irrelevant, has to be held apart.
We gave this to a 115 older and younger monolingual and bilingual participants and the data I’m going to show you is how many times they said “yes” to sleep.
But of course they saw many many of these. Okay and there it is.
Monolingual, in red, are saying “yes” to sleep significantly more often than bilinguals — both in the younger and the older age groups interaction.
I want to change pace now and I’m going to talk about two studies with children so we can see where these differences come from.
Let’s try to go back to the origins a bit as kids are building up their abilities, both in language and in executive control, and see if we can find where bilingualism begins to diverge the developmental project trajectories.
The other point about this study I’m going to show you is that most of the research, and most of the research I’m going to show you tonight, compares two groups.
Group research is very hard to do because you have to believe that there’s nothing else that’s different besides what you say is different.
So to to get more convincing evidence, you need another way of approaching the research — where you’re not only comparing two groups but you’re looking either longitudinally at people, as they evolve, or some other kind of design.
This is a kind of a training study you might say.
We went into immersion programs in schools — two different immersion programs.
These are programs where children who speak English at home, and their parents only speak English to them, are sent to school with some other languages spoken with the idea that they will learn this other language.
We use continuous estimates of bilingualism.
In these studies — we had two studies — in the first study English-speaking children were sent to school where they were educated in Hebrew and in the second they were being educated in French.
Importantly all of these kids spoke English at home.
They were all monolingual at the time they began the program.
The other thing about these programs is: kids come and go. It’s kind of drop-in programs — in a sense — so you could start the program in kindergarten or you could start the program in 4th grade — and if you come in later the schools tend to give you kind of help getting your language skills up to level but you haven’t been in the program as long.
So we can look at how long they’ve been in the program separately from how much they know of the language.
These studies were done completely independently
It never occurred to us that we would think of combining these studies.
All the kids in these two studies receive different tasks but they all received a metalinguistic task and an executive control task — just different ones.
We looked at the data with regression models which are essentially correlations.
We want to see which of these factors is correlated with good performance on the metalinguistic task and on the executive control task.
We looked at age because you can see these kids cover a bit of an age range.
We looked at how smart they are — just a basic spatial intelligence task.
We gave them an English vocabulary test.
They’re all English native speakers — but some kids are more verbal than others.
We created a score where we took a ratio between their English vocabulary and their other language vocabulary — because we could measure that.
So the closer that score came to 1, the more bilingual they were (nobody got one) and an estimate of how many months — we measured this in months — how long have they been in the program.
So which of these factors matters more?
They’re color coded because they cluster that way.
So age you just have to take out right away.
Intelligence and English vocabulary is kind of how smart they are and the two green measures how bilingual they are.
okay so Metalinguistic Task Study 1 gave them a Morphological Awareness Task and here’s what we found:
First: purple is unexplained — which is not an unusual finding.
Older kids are doing better. What you see here is that a big chunk, a quarter of the variance, is explained by how smart they are — what’s their English vocabulary and how smart they are.
In Study 2, they got a completely different metalinguistic task.
They’re completely different kids in a different immersion program and we get exactly the same results.
Those are about as close as you can get
So that’s what’s predicting how well they’ll do on a metalinguistic task — basically how smart they are and how verbal they are.
In each study, the kids also did an Executive Control Task but different ones.
In the first study, they did a Flanker Task and now there’s no trace of red. The only significant chunk of variance here is how bilingual they are.
The longer they’ve been in the program, and the higher that language balanced ratio, the better they’re doing on this Flanker Task.
As they’re becoming more bilingual, they’re doing better on an executive control task, but they’re not doing better on a metalinguistic task
The other study: different tasks, same results.
So we can see then that the more language proficiency kids have, the better their metalinguistic outcomes.
But the more bilingual experience they have, the better their executive control outcomes.
This is more subtle — comparing groups — the second Children Study I want to tell you about looks at level of socioeconomic status.
There has been a discussion in the literature, especially in the children’s literature –you don’t see it quite as much in the adult literature — that the effects that have been reported for bilingualism are actually socioeconomic status effects and that the two are confounded.
The bilingual children in our studies just have higher SES than the monolingual children and that’s what’s really driving it.
It’s an important argument because it’s well known that SES has a very powerful effect on children’s development and performance and, in particular, it brings it down if you’re low SES.
Lower SES children have lower Vocabulary Scores and lower Executive Function Scores.
We did a study where we could include variations both in bilingualism and in SES.
We did a very subtle manipulation in the literature that other Thummim estimates that compares SES for children — typically middle class children — are compared with very poor children who are at risk from all sorts of other things and not surprisingly do poorly in school.
We didn’t do that.
We picked kids who we called working-class children and others that we called middle class children.
The difference is how much education their mothers have.
The working-class children had mothers with basically a high school degree and the middle class children had mothers with a college or university degree.
But nobody was at risk.
Everybody lived in nice homes and, importantly, most of these kids went to the same schools and all of these kids sat together in the same classrooms and listened to the same teachers.
These classifications, by which we compared their data, were based only on their maternal education and their status as bilinguals.
These are standard scores. These are z-scores — so anything that goes up reflects a score that’s higher than the group average anything that goes down is lower than the group average.
Again, monolingual in red, bilingual in blue, but now working-class in solid lines start with the right panel with the language scores.
What you see is that both red bars go up
Irrespective of SES, monolingual kids are doing better on the language tasks than bilingual kids.
There’s also an SES effect.
The middle-class kids are doing better than the working-class kids — but the pattern is the same.
Now look at Executive Control Tasks.
The bars flip and now, irrespective of SES, bilingual kids are poking up and the monolingual kids are poking down.
And again, with the main effect of SES, these bars are higher than those bars — so what does this tell us?
It tells us that whatever effect SES has — and it does, even in this very subtle manipulation of SES — the effect of bilingualism is in the —
I showed you in that earlier slide, where I put data from a number of different age groups together, that it’s hard to find these effects in young adults.
So I want to turn for a minute to a study that was done by a former PhD student of mine Gigi Look.
Her point is that you can’t just classify people as being monolingual or bilingual because there are so many different aspects of bilingual experience and so she likes to describe this as the Monolingual Bilingual Continuum.
We don’t know what happens in the middle.
What she did is bring into the lab a large group of people who she did not classify. She just tested and then quantified a guess.
She gave everybody scores from a number of measures on how bilingual they are — which is calling proficiency — and how much bilingualism they use.
Proficiency versus usage.
And if she took the whole sample, they would scatter something like that.
Up here these are higher.
These are people who really are fluent in two languages and use both all the time.
These are people who really have very poor proficiency in one of the languages and don’t use it very much.
In our research, where I’m showing you comparisons between groups, we only accept people like this as part of the bilingual group.
So she could create this scatter plot and then through median splits produce four groups that vary in how proficient they are and how much they use both languages.
Those are the real bilinguals.
Those might be ESL — and she gave them two different executive control tasks — it doesn’t matter what they are, the thing is that in each task there’s a baseline condition that has no conflict — it’s really simple — a congruent condition where there’s no conflict (but there’s more information) — and an incongruent or conflict condition.
She was able to create a factor score that captured the data from those two tasks to see how people in those quadrants perform on the factors score for executive control.
She added 40 monolinguals.
Here are the results.
These are cost.
What she did was take that very simple condition and compare it to the easy congruent condition.
How much harder is it to do the easy condition?
Here are the real bilinguals.
Here are the real monolinguals.
These are the other three groups.
There’s no difference.
They’re all exactly the same.
When we look at the conflict condition, it changes — because now there’s a significant difference between the bilinguals and the monolinguals.
Higher means higher cost.
The conflict condition is more effortful and the monolinguals are having more trouble than the actual bilinguals.
But nobody in between is significantly different.
This means that if you compare almost monolinguals and most bilinguals they won’t be different.
It’s a subtle effect.
So, if you really want the performance to demonstrate something underlying in the cognitive system, you’ve got to be really clear and really careful about what you’re calling bilingual experience.
Finally, as I did with children, I want to give you a flavor of how we can look at this in an emerging way through training.
This is a recent study that we did with young adults who entered first year university as monolinguals. We found a group of them who enrolled for introductory Spanish and another group who enrolled for introductory psychology.
They’re all monolingual.
These are both for a full year courses in the same University — so they’re basically the same pool of students.
We tested them at the beginning and at the end of the year on a number of measures.
We gave them verbal and nonverbal executive control tasks and one of the tasks was a go/no-go task that they did in EEG.
We did that because go/no-go has very well known electrophysiological properties.
We know exactly how to find good performance in N2 P3 complex shows us the level of proficiency in that task.
There are now, I think, three studies published showing that if you compare monolinguals and bilinguals doing a go/no-go task the bilinguals typically have a larger amplitude on the N2 P3 waveform so we know that’s what we’re looking for.
But these are monolinguals.
First of all, these are their reaction times — before the year and after the year — on go/no-go trials.
Everybody’s identical. There is no trace of difference in how fast or how well they’re performing this task.
But when we look at their brains, we do see a difference.
For the Spanish learners, after the year, there’s an increase — a significant increase — in the amplitude of the p3 not on the end – it shifts a little bit in latency but the significant shift is in the amplitude of the p3.
They’re not looking like bilinguals yet but they’re starting to change.
Their brain is starting to change the way it’s responding to this task.
I said at the beginning that these changes can be found across the lifespan and so I’m going to move now into older age.
I’m going to change also what I’m looking at because there’s very little evidence that bilingualism does anything important or protective for memory.
Let’s face it memory is what we’re all worried about right?
That’s what we really want to protect.
So it’s very nice that bilinguals can do assignment tasks faster but really what’s that going to buy you when you’re older and you can’t remember where your keys are?
We need to see if there’s any penetration of these effects into regions that might have more practical importance — because the main behavioral effect we’ve been showing is on executive control.
The one aspect of memory that might be impacted is working memory, because working memory — the ability to hold information in mind and manipulate it — is part of the executive control complex.
Maybe we can find some effects in working memory but the evidence is mixed — there are a half a dozen studies but the evidence is very mixed — and yet we need to be able to find a link into what we would just call plain episodic memory, so possibly some aspect of working memory.
Okay. So here’s a recent study where we had younger and older adults who were matched on all kinds of things.
That’s just a lot of boring numbers.
These are very well matched groups and what we’re going to do is give them a non-verbal working memory task that’s very difficult.
You see a panel with four crazy figures that are impossible to label and then there’s a blank and then you see a single figure.
What you have to do is yes or no.
“Was this figure on the panel you just saw?” and in this case you’d say, “yes”.
And then you move on and you do another trial, another blank, another probe, and in this case you’d say, “yes” because you just saw it.
Okay so that case, because the same probe figure just appear twice, that’s pretty easy.
You’ve seen it.
It’s safe to say yes.
The crucial condition is interference.
You start with the same setup and you say yes and then you get a new panel and a new probe but now you have to say no because it isn’t on this panel but it was — oh dear I didn’t try to paste it what’s complete it was on the previous panel.
You have just seen it and when you see a run of 50 of these it’s really hard to remember if you just saw — did I see you two ago, did I make it up?
It gets very confusing. So on the interference trials you have to say no, but it’s interfering — because you actually saw it on n minus one.
The way you keep these straight — again it’s a lot like that sleep thing — is the Executive Control System.
Here are the results on Facilitation Trials.
What I’m plotting is how much better they do on these easy trials than on Baseline Trials.
I didn’t show you the Baseline Trials.
You can imagine.
So that’s how much better they’re doing.
And on the Interference Trials, this is how much worse they’re doing on those Interference Trials than on a Baseline Trial.
What you can see again — in both younger and older adults — is a little more facilitation in bilinguals, a little more pushup, but a lot less interference.
Exactly like the sleep thing.
They can keep it straight now.
This idea of facilitation and interference, we’ve shown a couple of times, this is a replication of that study where we used easier materials.
Those figures are really really difficult.
So we used wingdings and we got the same results in that study.
We’ve done it with a Stroop task.
You name the font color.
In both cases you have to say red but you can see there’s interference.
And we got the same results
So what bilinguals are doing is they’re coping with interference in these very simple rapid presentations.
They can keep things straight.
They can keep their eye on the ball.
Now that’s all very nice — and we’re very careful, when we select older adults for our studies, that they’re all healthy older adults. But the real question would be what happens if aging is not proceeding in a normal healthy way?
Is there any residual benefit of bilingualism once aging begins to impair memory and cognitive function?
Remember the first signs of dementia are memory loss — and the bilingual benefit is in executive control.
I’m going to show you very quickly the first two studies we did on looking at the onset of symptoms of dementia in monolinguals and bilinguals.
All we did is go into the clinic and look at hospital records.
We never saw any of these people.
This is information that we took from the records.
In the first study most of the patients — two-thirds of the patients — had a diagnosis of probable Alzheimer’s.
In the second study they were all Alzheimer’s patients.
Here’s what we found:
We had about 90 monolinguals and 90 bilinguals.
There were another hundred records — hundred or so records — that we took from that sample (that we did not include in the analysis because we couldn’t be sure whether we wanted to call the monolingual or bilingual).
As I showed you, a few slides back, it’s really important that you get those classifications right.
These people are matched on a number of things.
Bilinguals with less formal education, that’s a deficit. They should be showing symptoms of dementia earlier than monolinguals.
They have the same overall level mini-mental scores.
Everything’s the same.
How old are they?
The bilinguals are four and a half years older when the symptoms become apparent.
Four and a half years is an enormous time in this world.
So we repeated the study — selecting only probable Alzheimer’s patients.
Again, there’s a few more of them now matched in the same way and we get pretty much the same difference.
So now the bilinguals are about five years older when their families first notice symptoms.
Now there’s a study that was done Thomas Beck at the University of Edinburgh — who might be here (I want to give him full credit) — there he is, hi Tom.
This is a fantastic study that Thomas did, in collaboration with his colleagues in India, where they follow the same procedure but a completely different population.
Everything is different about this environment.
Nobody’s an immigrant.
Many are uneducated.
Some are illiterate.
A very different demographic base.
But they follow the basic approach that we had followed on a larger sample and, importantly, included a variety of dementias.
I’ll come back to that in a minute.
They found exactly the same lag.
The bilinguals in their study, on average were four and a half years older, than the monolinguals.
This even applied to illiterate and uneducated bilinguals.
In fact, the effects were larger in those groups.
They found this effect for all subtypes except dementia with Lewy bodies which is parkinsonian dementia.
There is a strong association between Parkinson’s disease and executive control dysfunction.
Hold that thought.
All right now back step one more minute before full-blown Alzheimer’s.
There’s often a diagnosis of mild cognitive impairment and this is just the beginnings of things about to go wrong.
Most amnestic mild cognitive impairment progresses to Alzheimer’s disease.
But crucially there’s two subtypes: single domain and multiple domain.
In single domain, the patient is only exhibiting memory problems –can’t find their keys.
In multiple domain, there’s that memory problem plus something else and that something else is generally an executive function deficit.
We took monolinguals and bilinguals who had been diagnosed with a single or multiple domain — mild cognitive impairment — and we looked at how old they were when the symptoms were first notice and their equivalent on everything else.
For single domain, the bilinguals again are a nice five years older and on the multiple domain they’re not older at all.
The effect is gone — disappeared.
Now let’s just look for one more second at mild cognitive impairment.
It’s progressing in the same way as Alzheimer’s.
I’ve inserted this slide just to show you that you don’t need to rely on between-groups comparisons that are fraught with all of these operability issues.
We can look at incidents — you know an incident study takes a large group of people who are perfectly healthy and tests them and then sits back and waits for them to become demented.
What it’s doing is cumulatively plotting how many people have MCI (Mild Cognitive Impairment) as a function of their language experience.
The dotted line [patients] have no experience with any other language than English and they are on the rise to MCI.
The bottom line — this whole thing is couched in terms of foreign language instruction but really the solid line on the bottom are bilinguals
People who really know another language, they stay significantly lower — lower incidence — slower to develop the symptoms, a less severe rise.
That is just so you’ll believe me when I say in between-groups-comparisons, the bilinguals are doing better.
So finally, let’s just look at all of it together.
What I plotted here is age of diagnosis.
I’ve shown you Study 1.
In study 2 these are the EC studies.
I didn’t show you these data but you can see — if you just scan that figure — all of the blue bilingual bars are recording an older age of diagnosis except the one case where there’s an EC impairment.
I refer you again to the Alladi Study in India where the dementia that included EC impairment did not prevail, bilinguals were not protected in the same way.
So that’s pretty nice. You can look at that and say yeah you know it’s postponing dementia a bit but these people are all older than me why should I care? Does this really matter?
Last week, in The New York Times, in an op-ed piece was the following: delaying the average onset of the disease by just five years — which is exactly what we have — would reduce the number of Americans with Alzheimer’s in 2050 by 42% and cut costs by 1/3.
Newt Gingrich presented this argument to appeal to the government to get double the budget of NIH — double the budget of NIH — because he’s scared.
All right. What have we got across the lifespan? There are bilingual advantages in performing certain tasks.
There are bilingual difficulties with some tasks but nothing is simple.
There are no one-to-one correspondences.
There are no effects that don’t include interactions with other factors.
Both verbal and nonverbal processing are carried out differently in bilinguals.
I would add “carried out differently in bilinguals”, in different contexts.
Think back to the sand and the cross-country ski tracks.
The sand tracks carry the mark of the experience and the tracks allow you move faster if you keep moving on them.
But you know well that these have to be maintained, through experience, for those effects to be seen.
I think most dramatically we’ve seen that this executive control may provide compensation for other processes like episodic memory that are carried out in a completely different part of the brain and thereby provide some protection against symptoms of dementia –not against the disease.
The bilinguals have the disease.
Their brains show more advanced evidence of the disease.
But their behavior doesn’t.
That’s cognitive reserve and altogether I would submit that this is powerful evidence for experience dependent neuroplasticity.
FEATURED IMAGE CREDIT: Roland Tanglao