I like you ’cos you’re like me – or why my enemy’s enemy is my friend

Poor hipsters and their problems – life’s much simpler for kids

Kids’ social instincts emerge early [1,2]. Newborns prefer to look at human faces over other inanimate objects, especially attractive faces. Soon after, babies begin to evaluate the social actions of others: at three months they prefer to play with toy characters that they’ve seen be kind or helpful to another toy, and avoid mean, antisocial individuals [3].

By 9–12 months of age, toddlers understand that other people also share this preference: that is, they appreciate that someone else who has been helped or hindered in trying to achieve a goal will prefer the helper over the hinderer [4]. Three-year olds will also chastise and punish ‘naughty’ puppets, including those that harm other puppets (if only mildly) [5]. Together, these findings suggest that the basic psychological ingredients of full-blown morality are well established by the fourth year of life.

Some of the other social preferences that infants during this period are a little less morally positive, some even xenophobic. Six-month olds prefer to look at photos of people that speak their native language, and 10-month olds are more likely to accept gifts, such as a toy, from someone  speaking their own language [6]. Infants’ social preferences also develop an egocentric streak: by their first birthday, they show a preference for people who are similar to them, even if that only means liking the same kinds of food [7].

A new paper in Psychological Science from the lab of Yale University’s Karen Wynn — a leader in studies of moral development who has been  involved in many of the studies alluded to above — shows how these moralistic and self-referential aspects of social thought are intertwined as infants enter their second year [8]. Working with Kiley Hamlin, Neha Mahajan and Zoe Liberman, Wynn wanted to know whether the tendency to like (or dislike) people who help (or harm) others is affected by how similar the helper (or harmer) is to the child — and whether there would be any difference between younger children, around 9 months, and 14-month olds.

To find out, the team set up the following experiment. To begin with, the 9- and 14-month toddlers were offered graham crackers (a kind of simple biscuit) or green beans, to see which they preferred. (Most kids went for the biscuit.). They then watched a puppet show in which two rabbits ate the ate crackers and beans. While tasting these snacks one rabbit said “Mmm, yum! I like crackers!” and “Ew, yuck! I don’t like green beans!”, while the other expressed the opposite food preference.

Depending on the kid’s own food preferences, these defined the ‘similar’ and ‘dissimilar’ rabbits for the next part of the experiment. This involved the kids watching another puppet show in which a rabbit — either the similar or dissimilar one — bounced a ball on a stage flanked by two new dog puppets on either side. Occasionally, the rabbit would drop the ball, which would roll towards one of the dogs on either side of the stage. One dog was helpful, and would return the ball to the rabbit. The other, however, was mischievous and would run off with rabbit’s ball — which, in this experiment, constituted harming the rabbit puppet. (In these studies, the ball went from helper to harmer dog alternately.) After watching this show, the babies were sat with the dog puppets. The point was to see which one they would liked most — that is, which one they looked at and reached for first.

Eight out of eight 14-month-olds who watched a ‘similar’ rabbit dropping the ball preferred the dog who helped the rabbit carry on, while eight who watched a ‘dissimilar’ rabbit reached out for the unhelpful or harming dog. The 9-month-olds showed the same pattern of preferences, but just less strongly: 75% preferred the helper dog with the similar rabbit, and 81% the harmful dog with the dissimilar rabbit.

This suggests that this capacity for flexible social preferences based on a sense of sameness or similarity emerges early, and is robust shortly after the first birthday. But what, exactly, are these preferences? It might seem obvious — infants like people who help similar others, and like people who harm dissimilar others — but there are other possibilities. For example, infants could be neutral rather than positive about people who help others who are similar to themselves. In which case, the reason why kids pick puppets that have helped similar others over puppets who have harmed them is that they don’t like the harmers, not that they particularly like the helper. Conversely, infants might be neutral about people who harm dissimilar people, but dislike those who helper them — and so they pick, by default, the dog that harms the dissimilar rabbit.

To tease out these nuanced but important differences, Wynn and colleagues essentially re-ran the previous experiments but with a couple of key differences. The first change was that between meeting the similar/dissimilar rabbits and seeing the show in which they were helped or hindered, infants were introduced to a neutral character who simply jumped up and down. The second tweak was in the choice that the infants had to make in the final stage: whereas previously it had been between the helper/harmer dog, now it was between either the helper/neutral or harmer/neutral. In these studies, the neutral character acted as a baseline against which other choices could be compared.

Repeating the previous findings, the toddlers who watched a show with a similar puppet preferred the helpful dog to the neutral character; likewise, they preferred the neutral character to the harmer dog. And again, when the rabbit show was performed by the dissimilar performer, infants preferred harmer to neutral, and neutral to helpful.

So it seems that infants really do like people who help others who happen to be similar to themselves, and feel the same about people who visit harm upon those who differ in some way. At the same time, they don’t like people who harm those who they deem to be similar to themselves, and nor do they like people who help people with different tastes. This flexible social morality is clearly observable by 9 months, and is robustly in place by 14 months.

I have to confess that I find these findings dispiriting. We like to imagine that children are born ethically pure and innocent, without the baggage and prejudices of us world-weary adults. We’d like our kids to embrace a universal ethics in which hurting people is bad whether they’re like us or not. To the extent that kids end up favouring some people over others, so much so that they like to see people cut from a different cloth treated badly, we might like to pin the blame on their upbringing. But this doesn’t seem to be the case: the roots of social divisiveness go back to the first year of life, perhaps even the first 6 months.

Of course, as we grow up there’s great scope to overcome these biases. As adults we don’t meaningfully divide the social world up into people whole do or don’t like broccoli. Unfortunately, the cultures we grow up in give us many new ways to split the world into broad groups of ‘us’ and ‘them’. The modern world is riven by seemingly intractable conflicts between groups who define their differences all too clearly in everything from the religion they espouse, the rituals they practice, and the ideologies they embrace to their culinary and sartorial preferences. Most of these groups operate, more or less explicitly, on the idea that my enemy’s enemy is my friend, and that it’s good when bad things happen to the other side. (I recently wrote about the psychology of cultural conflict for New Scientist.)

Yet this perhaps bleak picture of the foundations of our social psychology has a positive side. Yes, children and adults are frequently prejudiced against people they perceive as different from themselves, but this often goes hand in hand with altruistic and compassionate feelings towards those that are deemed to fall into the same social or cultural groups that we inhabit. The biases revealed in this latest research are just another example of the Janus-faced nature of human sociality and solidarity: love for our ingroup and enmity towards outgroups increasingly look like two side sides of the same coin. We may not like it, but this is part of the triumph and tragedy of the human condition.

P.S. You can listen to Kiley Hamlin in conversation with Jonathan Phillips here at BloggingHeads.tv

UPDATE: I missed this, but monkeys also stay away from meanies, according to new research published in Nature Communications.


1. Gopnik, A., Meltzoff, A. & Kuhl, P. (1999). How Babies Think: The Science of Childhood (London: Weidenfield & Nicholson).
2. Bloom, P. (2004). Descartes’ Baby: How the Science of Child Development Explains What Makes Us Human (New York: Basic Books).
3. Hamlin, J. K., Wynn, K. & Bloom, P. (2010). Three-month-olds show a negativity bias in their social evaluations. Developmental Science 13, 923–929.
4. Kuhlmeier, V., Wynn, K. & Bloom, P. (2003). Attribution of dispositional states by 12-months-olds. Psychological Science 14, 402–408.
5. Vaish, A. Missana, M. & Tomasello, M. (2011) Three-year-old children intervene in third-party moral transgressions. British Journal of Developmental Psychology 29, 124–130.
6. Kinzler, K. D., Dupoux, E. & Spelke, E. S. (2007). The native language of social cognition. PNAS 104, 12577–12580.
7. Mahajan, N. & Wynn, K. (2012). Origins of “us” versus “them”: prelinguistic infants prefer similar others. Cognition 124, 227–233.
8. Hamlin, J. K., Mahajan, N., Liberman, Z. & Wynn, K. (2013). Not like me = bad: infants prefer those who harm dissimilar others. Psychological Science (OnlineFirst) DOI: 10.1177/0956797612457785


About Dan Jones

Dan Jones is a freelance science writer
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