to deliver more candies to the other child or none to either,
4-year-olds often opt to trash all the sweets (PLOS ONE, 2013).
“They’d rather have none than one” if another child is poised to
get more, says Warneken, a study co-author.
Just because children understand fairness, though,
doesn’t mean they practice it. In a pair of studies, Blake
and McAuliffe showed that most 4- to 7-year-olds rejected
situations in which they’d receive a smaller share of candy or
stickers, but accepted inequality if they were in line to get the
larger pile — even when they said sharing was the right thing
to do. “Children seem to endorse equality, but they don’t
always use it,” Warneken says. That thinking seems to shift
at around age 7 or 8, the researchers found (Cognition, 2011;
PLOS ONE, 2013).
Before then, kids actually seem to prefer an unfair situation
when it gives them the upper hand. Wynn and colleagues gave
5-year-olds a chance to choose a pile of tokens they could trade
in for a prize. They found kids preferred to take seven tokens if
another child would get none, rather than eight tokens for both
“Young kids are actually extremely self-interested and are
in fact angling positively towards basic unfairness,” says Wynn.
“When put together with the infant findings, this highlights
an important distinction between what babies and kids want
others to do, and what they want for themselves.”
Inclined to be kind?
Other research by Sommerville suggests that fairness and
generosity are intertwined from as early as age 1. In an experiment
similar to Baillargeon’s giraffe study, she found that 15-month-
olds who were most surprised by an unfair cracker quota were
more likely to share their favored toy (PLOS ONE, 2011).
Because other research indicates that recognition of
fairness emerges between 9 months and 12 months of age,
Sommerville says the 15-month-olds who were less sensitive
to injustice probably weren’t just lagging behind their peers on
that developmental milestone. “We actually think that we are
starting to tap into some of the individual differences that will
persist over time,” she says.
Individual differences aside, certain social situations may
inspire a person to act more or less morally. Warneken and his
colleagues demonstrated this idea in an experiment designed to
test fairness in action.
The researchers rigged a system in which two kids had to
work together to pull a rope to lift a box with marbles inside.
Starting around age 3, they found, the children were inclined to
share the marbles if they had worked together to retrieve them.
If one child ended up with three marbles while her partner got
just one, she’d share so that they each had two. However, if the
kids worked side-by-side independently to get the marbles, they
weren’t bothered if they each ended up with a different number
in the end.
In that regard, 3-year-olds are a step ahead of our primate
One of us
cousins. Warneken and his colleagues ran the same experiment
with chimpanzees, and found that the apes were willing to
team up to retrieve food rewards. But if one chimp ended up
with more snacks than its partner, it happily kept them all
(Nature, 2012). An early sense of fairness may have evolved
to help humans work together to survive, Warneken suggests.
“Collaborative work is the cradle of equality,” he says.
Evidence is also mounting that babies understand the concept
of “us” versus “them” from an early age.
In one example, Wynn, Hamlin and colleagues asked
9-month-old and 14-month-old babies to choose a food, either
graham crackers or green beans. Then the babies watched a
series of puppet shows in which one puppet liked crackers and
the other preferred green beans. Infants in both age groups
preferred characters who were nice to the puppet that shared
That was in line with previous findings and not unexpected.
But the next finding surprised the researchers: The babies also
had a clear preference for characters who were mean to the
dissimilar puppet (Psychological Science, 2013).
Wynn is hesitant to describe her findings in the
psychological lingo of “in-groups” and “out-groups” since it’s
unclear whether babies are constructing social groups around
these shared food preferences. “It seems to be fundamentally
about a shared preference: You value aspects of the world the
same way I do, so I like you,” she says.
Other studies suggest that while babies recognize social
groups, they don’t necessarily expect prejudice toward people
outside the group. Baillargeon has run studies in which
experimenters identify themselves as members of made-up
social groups by announcing, for instance, “I am a lumi” or
“I am a tarfen.” She’s found that 16-month-old babies are
surprised when a person fails to help another member of
his or her group. However, the babies in her studies seem to
have no expectations about whether a person should help an
outsider, she says. “If they aren’t part of your club, you have a
choice in whether or not to get involved.”
As scientists continue to study infants’ social and moral
development, one big question remains unanswered: Are social-
moral principles learned, or are babies born with these systems
already in place?
One important clue may come from cross-cultural studies,
which can help illuminate how and when babies from different
cultures exhibit various social behaviors, researchers say. But
such studies just haven’t been done yet.
“Studying babies is pure, in a way. It can tell us how our
social and moral processes develop before they’re muddied up
by culture or language or complex reasoning,” Baillargeon says.
“When you look at babies, it’s magical.” n
Kirsten Weir is a journalist in Minneapolis.