Question: Can monkeys have human-like prejudices?
Laurie Santos: Our newest line of work is actually
trying to explore whether or not the monkeys share some of the aspects
of human social cognition that we’re not very proud of. So these are
things like the fact that we are very, very prejudiced. Even though we
don’t realize we are, we have these implicit biases against out-group
members, against individuals of different religions, different races and
so on. And these biases play themselves out in really insidious ways.
We’d really like to know how these biases work, but there are lots of
possibilities on the table for where they come from. Like, you know, we
grow up in a biased society, there are lots of kinds of cultural
influences that are biases. Are these the real culprits, or is it
something a little bit deeper? Is it something maybe older that might
be harder to override?
So we actually started studying whether
the monkeys share some of our human-like prejudice against the
out-group. Our first study really just asks this in a really simple way.
We said, "Do monkeys spontaneously distinguish between guys that are in
their in-group and guys that are in the out-group?" So the experiment
was super-simple. We did this down at our field site in Puerto Rico,
where we study Rhesus monkeys. Monkeys free range around and we sort of
showed up with this sort of big billboard which had two covers at the
end of it. When we opened the covers, there were two pictures of
different monkeys. One guy from their group and one guy from their
out-group. And the really simple measure was, do the monkeys increase
their vigilance, kind of get worried about it and stare at more the guy
that is in the out-group? Again, this is you know, first trial monkeys
that have ever really seen this weird billboard set up. But we found the
expected result what you might expect from humans, which is that,
spontaneously the monkeys actually direct their vigilance towards the
guy who is in their out-group. The worrying thing seems to be very
similar to the way that humans can devote their attention to out-group
And in our next line of studies, we wanted to see,
"Well, are they just kind of looking longer at these guys, or do they
actually treat them differently?" In other words, do they associate
them with bad things in their environment? And there’s a long line of
studies in people trying to look at whether people do this implicitly.
There’s a study known as the "Implicit Association Test" which basically
asks you to do a couple of categorizations. You’re categorizing good
and bad words, and you’re also categorizing in-group and out-group
members, you know say, your religion versus a different religion.
And using this task, researchers have shown that it’s actually very
hard to categorize your in-group with the bad words, and your out-group
with the good words. You’re actually slower and you make more errors
when these categories don’t match up. Suggesting that even though we
don’t like to think we do, we have these biases against out-group
members that can play out in these really simple contexts.
So we basically did the same categorization measure with our monkeys.
We gave them kind of series of different pictures that either matched in
their valance. So they were all kind of good images to the monkeys, or
they were all bad images to the monkeys. The idea in those cases was
the monkey should get bored, kind of good thing, good thing, good thing,
or bad thing, bad thing, bad thing. Or we set up a list of pictures
where the valances differed. And one of these cases was one of pictures
of their in-group members and pictures of bad things in this case scary
spiders. And what you found was that when the valances were
inconsistent—so in other words, when the in-group members were paired
with these bad spiders—that actually increased the monkeys' processing
time suggesting they don’t treat those categories the same way. However,
when you put out-group members with bad things, like spiders, they
actually process them very quickly suggesting that, to a monkey a member
of it’s out-group is basically, in some sense, equivalent emotionally
or in terms of its valance to this scary predator spider creature.
Same thing when we tried to look at positive images. So, in-group
members, the monkeys seems to process, like fruits really positive, you
know, good images that they want to approach and come near. But not so
with out-group members. So, when you give them pictures of out-group
members paired with fruits, it actually takes them a lot of processing
time. What it seems like is that spontaneously the monkeys are setting
up the same associations that we humans are, where they are treating
out-group members like negative things and in-group members like
Question: Is it difficult to determine which monkeys are "in" and
which monkeys are "out" of the group?
For monkeys, in-groups and out-groups are very simple. For humans, it’s
not that simple, right? We can form groupings based on all kinds of
really stable social groups like our race, our gender, and so on. But
we also form groups on the fly. You know, we can be Red Sox fans or
Yankees fans. You know I can be the gray shirt-wearing person; you could
be a different color shirt-wearing person. Humans can turn these
things on really spontaneously. For the monkeys, it depends on how
they’re born. So the monkeys in this population are born into a
particular social group. It’s based on who they’re related to, so they
are born into a particular group, the females stay in that group for
their whole lives and the males actually switch groups.
the monkeys provide this really cool window because the females live in
these very stable groups that they’re going to be in for their whole
lives, where the males actually switch. And so the males actually, you
know, are in one group for a certain stage of their lives and then
switch to a new group. So they kind of, in some sense, have to update
their information about what group they’re in, who they like, and who
they don’t like and so on.
Question: What does the Rhesus monkeys’ behavior tell us about human
Laurie Santos: Our conclusion from this recent line of work suggests
that... first that monkeys actually spontaneously form associations,
form categories of out-groups in the same way that humans do. So, the
perhaps the exact same thing that humans do when they think about
individuals from a different race, the monkeys are doing when they are
thinking about individuals from a different social group. Beyond just
the fact that they categorize them, they also seem to valance them in
the same way as humans do. Mainly that they tend to think of the
in-group as a positive entity, maybe actually devote resources more to
the in-group, and they think of the out-group as a negative entity.
The thing in humans is that we know that this is true implicitly,
often explicitly people won’t express these prejudices. But it suggests
that whatever is going on at the implicit level might be a process
that’s evolutionarily quite old. And to us that suggests that getting
over these kinds of biases might even be harder than social
psychologists have thought before.
The monkey work is cool
because, what we think it’s telling us is something about the roots of
human sexism, human racism, human ageism, basically any form of human
group ism—we’re seeing the undercurrents of this in the same cognitive
processing we’re studying in the monkeys.
Recorded May 21, 2010
Interviewed by Andrew Dermont