La scuola

The natural world is full of extraordinary animals

with amazing life histories.

Yet, certain stories are more intriguing than others'.

The mysteries of a butterfly's life cycle,

or the strange biology of the emperor penguin.

Some of these creatures were surrounded by fantastic

myths and misunderstandings.

Others have only recently revealed their secrets.

These are the creatures that stand out from the crowd.

The curiosities that I find particularly fascinating.

At the turn of the 19th century,

a German horse called Hans hit the headlines.

It was claimed that he could perform

complicated mathematical calculations.

And Chinese records tell of a species of bamboo

that seems able to count the years,

for all individual plants growing in different parts of the world

flower at exactly the same time.

Can a horse and a plant truly count?

In 1891, a retired German mathematics teacher

called Wilhelm von Osten decided to do a very unusual thing.

He began to teach maths to his horse, Hans.

After four years, Hans was presented to the public

to demonstrate his remarkable abilities.

To everyone's amazement,

he was able to count the number of people in the audience,

perform complex arithmetic, read a clock,

recognise and identify playing cards,

and he knew the calendar of the whole year.

To signal the correct answer, Hans tapped his hoof.

He was accurate and consistent,

and was declared worldwide as the first horse genius.

It all seemed incredible.

Could Hans the horse really count?

And why might animals need to do so anyway?

Well, it could help them keep track of the number within a group.

They might need to know how many offspring they have.

And, for many animals, it's an advantage to know

if one quantity is smaller or larger than another.

Wild horses live in small bands

that can join up to form big herds of more than 100 animals.

They have a dominant stallion, and a firm pecking order.

Horses are not territorial,

and have no great need to know the exact numbers in their own herd.

Or another.

But they do sometimes make judgments about quantity

when choosing food.

This basic ability to judge differences in amounts

is the first step in the skill of counting.

But what methods might animals use to assess numbers?

There are several ways to keep count.

We can count precisely to very high numbers,

and have created number symbols that indicate exact amounts.

So, we know that the number five, for example, indicates five objects.

Even if we can't see them.

Perhaps animals judge quantity in a similar way,

and have their own pictorial shapes perhaps,

Another idea is that animals judge differences in amount

as an accumulation,

just like filling a measuring tube with a liquid.

Alternatively, the mind may have memory slots

that store a limited number of objects

in the same way as a filing cabinet stores cards.

So, there could be several different ways in which animals

judge quantity or amounts.

Hans the horse appeared to count very precisely to high numbers.

This seems an improbable feat for any animal.

But, recently, an extraordinary discovery showed that an insect

with a brain a fraction of the size of a horse's,

can count with great accuracy.

The ant.

In 2007,

researchers investigated how Tunisian desert ants

to find their way home from foraging trips across barren plains.

It's known that they use the sun to

set them up to use the right direction.

But how do they measure distance?

Experiments were performed to manipulate the ant's stride length

to see if they were counting the number of footsteps that they took.

Based on a featureless environment,

ants learned to travel home to a set point.

Then, stilt-like extensions were glued to their legs

to lengthen their stride.

These ants took the right number of steps,

but, because of the increased leg length,

they marched right past their goal.

So, ants are able to log the number of steps that they take,

perhaps not counting them in the way that we do,

but they do have an internal counter.

Unlike ants, horses have no need to count their steps,

so it's unlikely that they have an internal pedometer.

But they can, nonetheless, assess quantity.

Wild horses are highly social.

And, if one is harassed by flies,

it will seek to join the largest available group for protection.

So, horses can estimate numbers and recognise differences in size.

But this is a much simpler ability

than the counting that Hans the horse was doing.

In 1904, the German Board of Education

look for closely to Hans

They wondered if Hans' owner was using trickery

to feed him the answers.

To test this,

other members of the board were given questions and answers

to pose to Hans.

Incredibly, Hans still answered correctly.

Eminent psychologist Oskar Pfungst

then came to investigate Hans' skills further.

And confirmed that he appeared to understand numerology,

and the abstract idea of counting words associated with numbers.

For Hans to perform complex mathematics,

he would need to understand

much more than just differences in quantities.

He would need to recognise the fact that two

is smaller than six.

And that specific number symbols

always go with the corresponding amounts.

To count, he would also need to realise that numbers occur

in a set, repeatable sequence.

And that the last number counted

represents the total of the whole set.

In effect, that he'd answered the question, "How many do you have?"

It seems that many animals have a sense of number,

but few are conscious of an exact total.

For most animals, the ability to recognise an amount,

and to compare it to others, is all they need.

But could horses be an exception?

Could they have advanced counting skills?

In 2009, experiments showed

that horses could count to a certain level.

I'm going to take false apples,

ones that don't have a smell which might confuse the issue,

and show the horse one...

..two...

..three...

..four in here.

And one,

two...

..in there.

Now, then,

which do you want?

Thank you.

Yes.

Four.

Repeated tests of 14 horses

found that they consistently selected buckets

that contained a higher number of apples.

But that sense of number was limited -

they could only keep track of numbers up to about six, and no higher.

So, it seemed incredible

that Hans the horse had such advanced counting skills.

Perhaps he was being helped or trained in some way by his owner?

There is little doubt that most horses are very intelligent animals.

And, if they're given clear signals,

they can indeed learn to perform complicated routines.

Hans the horse was schooled for many years,

so, perhaps, he had developed an advanced understanding of numbers

when given clear instructions by his owner.

In the wild, horses communicate well with each other.

Wild Mustang use a complex silent body language,

that scientists call Equus.

It consists of a series of gestures,

that are much like signing for the deaf.

Every part of the horse conveys meaning.