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#### 能懂概率的鹦鹉

The parrots that understand probabilities

The kea is a particularly intelligent species of parrot

from New Zealand.

Now, research suggests that

these birds might be smarter than anyone expected,

even outperforming monkeys in some tasks.

These kea can use probabilities to

predict which hand a black token is most likely to be in

based on where the token is picked from and on who is doing the picking,

even combining information from different contexts.

The kea are great fun to work with.

They are some of the most intelligent birds I’ve ever met,

and they all have amazing personalities.

Amalia Bastos has been working with kea,

trying to find out whether they could predict uncertain future events.

Could they understand an event that happened with incomplete information?

Could they fill in the gaps?

So, if you imagine that I’m placing my hand into a jar

with mostly blue candies and a few yellow candies,

and I take something from that jar

but you can’t see what’s in my hand,

you might guess that I’ve taken a blue candy,

and we wanted to see if kea could do the same thing.

A group of captive kea were taught that black tokens,

and only black tokens, could be exchanged for food.

They then saw an experimenter take tokens from two jars,

without being able to see what was in each hand.

They chose a hand by tapping on it to get the token inside.

In the first experiment, the kea almost always preferred the jar

with the highest proportion of black tokens,

even when the actual number of black tokens in each was the same.

This suggests they were choosing the hand based on the probability of it containing a black token,

something only previously seen in great apes.

A second experiment showed

they could even take into account a barrier in the middle of the jar,

looking for the jars with the highest proportion of black tokens in the top section

and ignoring the rest.

So, kea have a complex social structure,

where many individuals can live in a group and they come and go as they please,

and that means they need to remember the identities of multiple individuals,

and they have to interact with multiple individuals,

and of course they need to remember all of these interactions.

So, we wanted to see whether kea could understand that

experimenters have biases or preferences when they make their selections.

For example, one person might select a yellow candy

even when the yellow candy is in the minority,

and another might select a yellow candy when they’re in the majority.

And what we can assume from that

is that the person who took yellow candy when it was in the minority

actually prefers yellow candies to blue candies.

The third part of the experiment tested their social skills.

The birds were shown two humans taking tokens from a jar.

One person looked into the jar

and deliberately picked one of very few black tokens.

When later offered a choice of experimenters,

the kea remembered this person

and their apparent preference for black tokens.

We were very surprised to find that

kea can use social cues, even from humans, to make these judgements.

Kea were looking at the biased experimenter,

understanding that they had a bias or a preference for a particular type of token,

and then selecting this person at test

when both experimenters had the same populations of tokens.

Reading human social cues like this

and remembering information about individuals to use when making predictions,

is another ability that’s so far only been shown in great apes.

Kea look very intelligent

and they behave very intelligently,

I just didn’t expect them to

perform quite as well as chimpanzees do.

This experiment marks the first evidence

that birds can make predictions about future events using probabilities,

and that they can combine information from different contexts

to make those predictions.

I can’t wait to see what kea do next

because they keep surprising us,

so I can’t wait to see what the next step brings.

OK, Plankton can you move?

OK, just a little bit…

You can’t stand in front of the camera! Huh?