The strange case of the former bank manager who is now able to read
only number words as the result of a neurodegenerative condition.
Brian Butterworth: What's fascinating about him is that he can only
read one sort of word. He can only read number words and it's never
been reported before and that's why we're so interested in it. But it's
theoretically very important because the standard theory of reading
goes something like this: that when you see a string of letters you do
two things simultaneously; you try and find the sound of that string of
letters. You might do that by taking each letter and finding the sound of
each letter and putting them together. You might try and recognise it
as a whole word and try and find the sound of the whole word but, at
the same time, you're trying to interpret the meaning of that string of
letters, you're trying to find the meaning of that word and these two
processes converge to give you the pronunciation of the word.
Now the problem with the theory up to now is that it's never really been
tested properly. We don't know whether you can pronounce the word
accurately just going via the meaning. So for example, if you see a
letter string like t-r-e-e- you get the meaning of a tree and then you
have to say what that meaning is. Now what we want to know is: is that
route via meaning sufficient to give you just "tree", and we haven't been
able to do that up to now.
This case is very interesting because this man can't use the route via
sound alone. We know this because if you give him a very simple
string of letters he hasn't seen before, like y-i-t- he can't say it. He
used to be able to say it but he can't say it anymore. Even if the letter
string sounds like a real word, like y-o-t- he still can't say it. Now the
other really interesting thing is that he can't say words that he doesn't
understand. So he can't say y-a-c-h-t says yacht either, he can only
say words that he does understand and if he does understand them
then he says them accurately. And we know that he has a very precise
understanding of numerical concepts because he can calculate
accurately. So he knows the difference between 1 and 2, and 3 and 4,
and 13 and 15 and he can read all these words with perfect accuracy,
but words he doesn't understand, and these are very common words
like "take" and "give", and yet he can't read because he doesn't
The reason why he doesn't understand them is because this
unfortunate neurodegenerative condition has affected the parts of the
brain that deal with language and other forms of general knowledge,
which is in his case in the left temporal lobe, but has spared the left
parietal lobe which is where numerical ideas are.
Robyn Williams: It's very interesting you gave the example of "tree"
just then. It's very close to "three' and I would have thought that one
little letter might be something that could help him on his way. Are you
telling me that he can read "three" but he can't read "tree"?
Brian Butterworth: That's exactly what I'm saying. Now all the
previous cases of reading problems due to brain damage have been
complicated by the fact that the patient either has very good word
meanings in general, in which case we've now shown that this route
via meanings is sufficient for reading words, or they've got some of the
letter to sound route still intact, and so although they might not really
understand "tree" they can maybe sound it out a bit and then get to the
pronunciation. But this man unfortunately can't get any of the letter
sound relationship. He can say number words OK and he can say a
few other sorts of words reasonably well, but not very many. So his
language is very affected too.
Robyn Williams: Now Brian, this is clearly significant because it's in
the journal "Nature" this month, "Neuroscience", and you're a
distinguished researcher in this field, but for innocent bystanders like
me, if you're looking at one case of a person who's got a very unusual
impairment how do you know that this is a window on the general
Brian Butterworth: There are two answers to this. First of all, it would
be impossible to do neuropsychology if you couldn't make
generalisations of single cases; therefore you must be able to make
generalisations of single cases. The other, perhaps more sensible
account goes something like this: that we have no reason to believe
that I H's brain was any different from yours or mine prior to his illness
and so his brain is likely to be organised at least for things that are
rather basic in a similar way to yours and mine. So we can get a clue
as to the organisation of what we would call higher mental functions
like calculation and language from these single cases, and it's actually
proved very effective as a way of investigating brain functions since
the time of Brocca in the 1860's. We can confirm some of these single
case findings by looking at functional brain imaging, seeing what the
brain is doing while it's doing it to see if the areas that we've identified
in these single cases are the areas that seem to be important for a
So for example, I believe in the case if I H that the temporal lobes are
involved in language and that the parietal lobes are involved in
number. We've done experiments and other people have done
experiments using functional imaging of normal people, people who do
speak and calculate normally. And we find that the temporal lobes are
very active during speech production and speech comprehension and
the parietal lobes are active during calculation, so we do have
independent grounds for thinking that the brain of I H is not at all
unrepresentative of humanity in general. I mean, one point that I
should make is that before his illness I H was a bank manager. Now
we assume that bank managers have normally organised brains.
Robyn Williams: Sometimes too organised.
Brian Butterworth: Sometimes. He was also and indeed still is an
addicted gambler, so he's obviously had a lot of experience with
numbers. So it may be that his number areas are larger and better
developed than mine are for example. However, one of the
consequences of his illness is that he's had to change his preferred
mode of gambling. It used to be horses, but in order to bet on horses
you have to be able to read the name of the horse. On the other hand,
if he goes to the dogs there are only six dogs in every race and you
usually identify each dog but its number. So you can go up and say
$10 on No.3 and that he does perfectly well and he still continues to
lose money in the normal way.
Robyn Williams: Poor man. However, here is a very interesting
example just to recap. He knows numbers, therefore he is able to read
something he understands and therefore he has this facility, but he
can't read non-number words. What does this tell you about how we
might approach reading in the first place? What does this tell you that
might be of assistance to treating people who've got reading difficulties
Brian Butterworth: As I said, the theory says and the theory now
seems better supported on the basis of this case, that when we see a
letter string we approach it in two separate ways; at least normal
people are trying to find the sounds of the individual letters and trying
to find the meaning of the letter string. Now some people, either
through brain injury or through some genetic abnormality known as
dyslexia, find it difficult to read by one or other system. And I think that
one of the implications of this is that you try and identify which system
it is that's affected in the individual and then try and exploit the intact
Robyn Williams: And so you've got a test, have you now?
Brian Butterworth: We've got tests and these tests have been
available for quite a long time. It's just that you very rarely get cases as
clear as this, so this tells us that we've been on the right track.
Robyn Williams: And what in the practical sense - how do you apply
this; having done the diagnosis on say a dyslexic patient, how do you
actually say right, now try this?
Brian Butterworth: Well, what you do is you try and encourage the
patient to, instead of sounding out letters if he's the type of patient that
I H is, to try and sound out the whole word. And you might give them
meaningful hints as to what those words are. So if it's "tree" you might
say, well think of what you see in the country.
Robyn Williams: Cows!
Brian Butterworth: Right.
Robyn Williams: Except in England, there's not many left.
Brian Butterworth: Yes, that's not a surefire way of doing it, but
certainly most children with dyslexia are going to have intact semantics
so they can use this route via meaning if that's the route that's
preserved or that's developed reasonably normally in their case. But
the case of I H is interesting from another point of view, which is that
we've been interested for quite a long time in how language and
numerical abilities are organised in the brain and it's these very clear
cases that can somehow tell you about that. For example, we reported
patients who have got very good language but very impaired numerical
abilities. So there was a patient that we reported some years ago who,
if you spoke to her, you wouldn't know there was anything wrong with
her, but because of her brain injury she wasn't able to do calculations
anymore. She couldn't in fact deal with numbers above 4 at all. Before
her stroke she'd had care of the books of the hotel that her family ran,
so she was pretty good a numbers prior to her injury.
Now people might say, well of course, if you've got brain damage
what's going to go first; Is it the stuff that you found hard? And so we
find language easy because we use it all the time but numbers are a
bit more difficult because you have to learn them at school. Cases like
I H say, well that can't be quite right, because here we've got
somebody whose language is gone, language of course which he's
used everyday, in his dreams even, but his numbers - he's very
practised with numbers but nevertheless he's not using numbers as
much as language. So numbers are still going to be, on those grounds,
slightly more difficult than language, yet it's his numerical abilities that
And so we now have evidence what
neuropsychologists like to call a double dissociation between language
and number. One type of patient has good language and terrible
numbers and this other type of patient, I H is the best reported
example so far, has got terrible language but very good numbers. So
we can see that in the brain these two processes are independent.
And in fact, we can look to the evolution of these two processes and
we can say, well maybe they have evolved independently as well,
because we know that infants, even in the first week of life, are
sensitive to the number of things that they see. So if you show a baby
of one week two objects, another two objects, another two objects,
another two objects, the baby loses interest. But then when you show
the baby three objects the baby suddenly starts to look.
Robyn Williams: Numbers, numbers.
Brian Butterworth: Numbers, numbers, numbers, that's right. So
you're born with this numerical ability and it seems that the brain
circuits that you're born with are in the parietal lobes and in the case of
I H those seem to have survived whereas unfortunately his
neurodegenerative condition has affected his language very severely.