Being impressed by the cognitive
abilities of a chimpanzee isn't just good for them,
it is good for us, because it helps us learn about
our own evolutionary history. Comparing the psychology
of humans to the psychology
of other primates is a great way to
illuminate what it is we
maintained, lost, or changed as our brains diverged
from other primates. Now, I'm really excited
right now, because in
the spirit of sharing, The Primate Research Institute
has agreed to show me some of the other ways
they're learning about us by studying those
who are<i> almost</i> us. <i> I'm heading to the
parasite lab to meet up</i> <i> with associate professor
Andrew McIntosh</i> <i> and doctoral student
Cecile Serabian.</i> <i> Their work with
Japanese macaques has
led them to theorize</i> <i> that primates' feelings
of repulsion or disgust</i> <i> could have served a protective
purpose in our evolution.</i> <i> To study disgust,
we will be working with</i> <i> one the most famous
disgust inducers: poop.</i> Andrew, Cecile, thank you
for meeting up with me, I can now tell people that
my time in Japan was crappy. [both chuckle] [Andrew] Just like
every day for us. So tell me, why is there
a bunch of poop on the table? Because we were studying
the social behavior and parasite infection
of the macaques. [Cecile continues] Right. If we want to say that humans
are somehow especially hygienic or disgusted by those kinds of
objects that might make us sick It's quite difficult
to separate whether that's an evolutionary
response to something or just a cultural
phenomenon that we've
kind of created on our own. [Michael]
Now these are clearly toys. They're made of plastic. These look
kind of different. Okay, so you have different
types here on the table. This is the type
for carnivores-- it's not the type of primates. Primates have a long-shape
type of poop. It's called type 9. -So those are all--
-Wait, poops have numbers? -[both chuckle]
-I only know number 2. Why make play poop when you
have plenty of chimps out there
giving you real poop to use? Ah. -So there's no odor
or texture here.
-Yeah, exactly. And what differences
did you see? [Cecile continues] Ah, so it's like a surface
to put the food on top of. -They would avoid the replica?
-Yes. [Cecile continues] [Michael]
Oh, really? Right, right. If you expose a bunch
of individuals to a range
of different kinds of avoidance experiments
we found that those individuals that
are much more hygienic actually were exhibiting
lower infection, so... It sounds like a really
strong argument in support
of the idea that we evolved an emotion like disgust - or a behavior like avoidance
of infectious-looking stuff.
-<i> Mm-hmm.</i> -Because it had an advantage. -You get infected less.
-[Andrew] That's right. So you have some kind
of experiment for me? -Yep.
-Is it safe? -Let's see.
-Don't play that way!
-[all laugh] <i> Cecile and Andrew wanted
to show me just how hard-wired
our sense of disgust is.</i> [Cecile] There you go. Okay. Those are edible? -Yes, those are edible.
-Mm-hmm. -I'm just going to place one
in each of the holes here.
-Okay. If you are ready to eat them,
just try to reach out for them. Okay. Okay. Good. Good. What do I do once
I pull the treat out? You will tell us
whether you are ready to
eat it or not, basically. Oh, okay. -So, you'll put one in there.
-One goes here. Sure. -One goes here...
-Okay. And one goes there. All right, I'm going to
start right in the middle. Hmm. All right, so I might just
blow on this before I eat it, but I feel pretty
ready to eat it. -Yeah?
-Because what I felt was dry, and it was solid,
it was like a foam. Watch. -Okay.
-Oh, it's really good.
It's got kind of a coffee taste. So far so good. I'm going to go to the left. No, I don't want this one. -Okay.
-Whoa, you still went for it. I still pulled it out. [sniffing] What was it? So I'm just going
to set it down. Okay. Alright, it smells...
it's kind of fishy. All right, now... [chuckles knowingly] I... okay. I'll tell you what,
that was disgusting in
terms of how it felt, but when I see the color, I see
this kind of bright green color that makes me feel less
disgusted actually because it's sort of a fun
color and it reminds me that it probably
isn't truly contaminated. But this is the one that
I'm least likely to want to eat. Even stronger than the visual
cues or the olfactory cues it seemed that that touching
some substrate like this gave us the strongest
aversive response. Yeah. So the first one you touched -was this piece of foam here.
-Yeah. -So yeah, it's basically dry.
-Solid. Um, then I think you
went here, and that
is called konnyaku. [Andrew]
Yeah, konnyaku is a kind of
starch-based gelatin which is part of
the cuisine here. You said it smelled fishy,
so in here you probably
have parts of seaweed. Yeah, right, that's where
that's coming from. It's soft, a bit wet,
but not very... -It's not sticking to me.
-Not sticky, yeah. And the last one here was
what maybe kids in the '90s including myself
were playing with. A slime toy. Which is like
slimy and sticky. And this,
it's just so gooey. Well, and the fact that it's
pink makes it so much more fun than if it was like, brown. Mm-hmm. Now, the research you're
doing with macaques, is that something
I could observe? We'd be willing to take you
out to the macaque habitat and we could run some of these
similar experiments with them -for you to observe.
-Ooh. I would love to. Yeah. <i> Cecile's work with macaque
monkeys on Koujima Island</i> <i> led her to develop
an experiment that she
and Andrew have been running</i> <i>on the macaques here at
the Primate Research Institute.</i> <i> They want to know if
macaques avoid feces</i> <i> because a feeling of disgust
evolved in order to reduce</i> <i> the risk of their
exposure to parasites.</i> -[Andrew] And here they are.
-[Michael] And here they are. Oh look at that,
the babies are so cute. -Here it's feeding time, almost.
-Mm-hm. Which is a good time
for an experiment. Yeah, we're a bit lucky,
they didn't eat that
much in the morning, so hopefully they'll have that
extra motivation to participate. And we're going to try
to play a bit with
the value of the food, -so we'll start with their
regular monkey chow.
-Right. Which they see a couple times
a day on a daily basis. And then we'll see what
happens when we introduce
that nice, tasty peanut. [Cecile speaking] [Michael] Right. And so, I'm
assuming they like peanuts. -Right, so--
-They don't like peanuts
in or on poop. Well hopefully, we'll
find that out today. [Michael] Okay,
so it looks like Andrew is dumping the, um... [Cecile]
Those are real feces that he is going to pair
with the replica feces that we have seen in the lab,
and a control brown wood chip. -[Michael] Near each other?
-[Cecile] Yes, near each other. Aha, all right. -Let the games begin.
-Yeah. <i> For the first trial, Andrew
places monkey chow on
the control block of wood,</i> <i> the replica feces
and the real feces.</i> <i> Whether or not the macaques
eat it may indicate their
level of disgust.</i> [Michael] They're looking...
now here comes one. -[Michael] No... oh, oh!
-[Cecile] Yeah. [Cecile]
No, he's smelling the wood chip. [Michael]
He smelled the wood chip,
the monkey chow fell off of it. [Cecile] Yes. [Michael]
Is he... gonna eat it? No. I think
regular old normal food
on poop is just-- it's a hard sell. [Andrew over radio] [Michael]
Shelled peanuts, okay. -[Cecile] So that's
on the fake poop.
-[Michael] Yep. -[Michael]
That's on the real poop.
-[Cecile] Yeah. -[Michael]
And that's on the wood block.
-[Cecile] Yes. <i> This time around, Andrew
introduces peanuts, which
the macaques really love.</i> <i>Will this special treat
override their inner instincts?</i> Oh, oh, they're
already running in. [both] Ooh. [Michael] But he threw it. -And he's washing it now.
-He's washing it. All right, here
comes another one. Oh, he went for the poop one! -[Cecile] Yeah.
-[Michael laughs] [Michael] The first one,
he just wants it to roll. -He doesn't even want
to have to carry it.
-[Cecile] In the water. This is rolling, so, they
do some of those behaviors. And now he's washing
it in the water, -[Cecile] Yeah.
-[Michael] Is it clean enough? Oh, still gotta roll. That was incredible,
because the peanuts that
were just on the wood chip, those went straight
into monkey mouths. <i> Was this an aberration?</i> <i> Andrew reloaded the peanut
baits to find out.</i> -[Michael] Decoy.
-[Cecile] A female is
approaching. [Michael] Yep, here she is. She smells it first,
and then-- and then-- -[Cecile] Smells it again.
-[Michael] Believes it, eats it. -[Cecile] On the fake.
-[Michael] That was
on the fake, yeah. Very cool. Now she already ate off
the decoy and it was safe. She hasn't, oh she put
the control right in her mouth. -[Cecile] Yes.
-[Michael] And she's going
to wash the real feces. [Cecile] Yeah. And she went for
the real feces last. Yes, she did. [Michael] She's got
a baby with her, so I really hope
she cleans that. [Cecile] Or maybe that's
the disadvantage, she's carrying a baby,
she cannot afford, like,
cleaning everything. Yeah. I'm really
amused by how they
visually recognize feces. -I mean we're far away,
it's hard for me to tell,
-Yes. but they can see that shape
or texture-- -"Be wary."
-Yeah. <i> Over the course of several
rounds of the experiment,</i> <i> the monkeys would eat off
of the control,</i> <i> wash food from the replica,
and be extremely hesitant</i> <i> towards anything
that touched poop.</i> <i> The macaques demonstrated
a clear and strong
sense of disgust</i> <i>that was driving their decision
making and potentially keeping
them safe from pathogens.</i> <i> With the experiment complete,
Dr. McIntosh returned topside</i> <i> so we could discuss
our findings.</i> So did you enjoy
the view from up here? [Michael]
They did exactly what we
talked about earlier. Ready to avoid, parasite
infested potential things. Yeah, I mean it's
pretty clear, there's not
a complete hesitation to pick up things
on actual feces but the reactions that
the monkeys give when they do so is just so clearly different
than when they are picking
things off the ground or off the control items
that they have here. Yeah, yeah, in fact,
I, you know, I only saw
a few trials here, but as soon as the peanut
or the monkey chow on
the feces is picked up and they realize that
the feces is coming with it it's a sticky substance
and that was when their
revulsion got larger. It almost seemed like they
might be absent-mindedly going
"I don't care," -and something deeper in them
was like, "you should care, you
should throw this,"
-<i> Yeah.</i> roll it, wash it,
so it makes sense from
an evolutionary standpoint. Well, Cecile, Andrew,
thank you again so much for
letting me come out here to see a primate
experiment in action. This was really phenomenal.
Thank you. -[both] You're welcome.
-Thanks for coming.
