The notion that people prefer similar others is as empirically-validated a research finding as they come in our field (see here, for example). Similar people make us feel better about ourselves, and who doesn’t like somebody that makes us feel better about ourselves? In fact, the preference for similarity is so common that it is considered a general characteristic of the human condition, and it’s not hard to imagine how preferring to hang around similar people, and avoiding dissimilar people, might benefit survival.
Recently, researchers have begun to identify exactly how early this preference for similar others begins to develop. One can’t help but wonder whether this “universal” preference for similar others is nature (i.e., we’re born with it) or nurture (i.e., others, such as our parents, teach us to like similar others and not like dissimilar others). For example, one recent study revealed that desire for similarity is evident early in life: “Infants prefer individuals who share their own preferences for food, clothing, or toys over those who have expressed contrasting preferences1.” But do these findings extend to the social world? In other words, at a very early age, do we prefer those who prefer people like us and dislike people different than us (i.e., “enemies of my enemies are my friends”)?
To test this idea, the researchers conducted two studies in which they put 9-month olds and 14-month olds through an ingenious protocol.2 The two different age groups allowed the researchers to test whether preferences for others change during the early part of life (thus providing some data on the nature vs. nurture distinction). The first study was broken up into four parts:
Part 1: Children indicated which they liked more: green beans or graham crackers. Shockingly (to this parent of a 4-year old and 2-year old), a healthy proportion of 14–month olds (31%) and 9-month olds (47%) preferred green beans. Silly kids.
Part 2: A researcher put on a two-rabbit puppet show during which each rabbit tried the two foods and either liked the same food as the child (i.e., the rabbit was a similar other) or disliked the same food as the child (i.e., the rabbit was a dissimilar other). Brilliant, I tell you. Brilliant.
Part 3: This was a puppet show encore involving either the similar rabbit puppet or the dissimilar rabbit puppet from Part 2, but now two dog puppets joined the action. In this show, the (similar or dissimilar) rabbit bounces and catches a ball, but at some point, drops the ball. One of the two new dog puppets – conveniently hanging out at the edges of the puppet show – either “picks up” the ball and returns it to the rabbit (i.e., the “helper”) or picks up the ball and takes off running (i.e., the “harmer”). The horror! Bad dog puppet! This scene was replayed until it was clear the kids were following the action on the stage.
Part 4: The kids had an opportunity to indicate which of the two dogs – the helper dog or the harmer dog – they preferred (i.e., which one did they reach for when given an option). The kids preferred the helper dog puppet (vs. the harmer dog that stole the similar rabbit’s ball) who helped the rabbit who ate similar food (graham cracker or green beans depending on what the kid chose). But remember…kids also saw a puppet show involving the dissimilar rabbit. What dog did they prefer in this case? You guessed it – the “harmer” dog that stole the dissimilar rabbit’s ball! Silly rabbit. Tricks are for kids.
Importantly, the results were the same for 9-month olds and 14-month olds. But, as the authors argue, because the kids chose between a helper and harmer dog, it’s not clear if the kids preferred the helper dog or wanted to avoid the harmer dog (e.g., in the similar rabbit condition). To address this limitation, they conducted a Study 2 in which the kids chose between either the helper or harmer dog and a neutral dog puppet they had not previously seen. Now the researchers could get a feel for the ‘direction’ of the effect, and it’s a good thing they did. With the neutral dog in the mix, 14-month olds in the similar rabbit condition preferred the helper dog to the neutral dog and preferred the neutral dog to the harmer dog. In the dissimilar other condition? You guessed it. Just the opposite pattern: the 14-month olds preferred the harmer dog to the neutral dog and preferred the neutral dog to the helper dog. But, unlike the 14-month olds, the 9-month olds showed no clear preferences when the neutral dog was in the mix.
The overall results lead to a pretty clear-cut conclusion: “Both 9- and 14-month-olds prefer individuals who harm dissimilar others over those who help them, and by 14 months of age, these evaluations are sufficiently strong to allow infants to distinguish helpful and harmful individuals from neutral ones.”
What’s really interesting about all this is that the kids didn’t show a preference for helpful vs. harmful “people”. Rather, kids like or dislike “people” based on how those “people” treat others and how similar or dissimilar the kid feels to those others. Or, as the authors eloquently stated, “…infants’ evaluations were specifically related to targets’ similarity to themselves rather than, for example, generally wishing graham-cracker lovers well and green-bean lovers harm.”
Now, exactly how it is that these patterns of preferences take root is tough to say. The differences between the 9-month olds and 14-month olds could reflect a learning process (e.g., 14 month olds have had longer to learn these preferences), or they could reflect more natural biological development (e.g., these preferences become more ingrained as the brain grows and matures). Most likely, it’s a bit of both at play.
So, for all your parents out there…keep an eye on your kids when they play with puppets, stuffed animals, or Pirate’s Booty (yes, even Pirate’s Booty is personified in my house). They just might clue you into how they view the social world around them.
Interested in learning more about relationships? Click here for other topics on Science of Relationships. Like us on Facebook or follow us on Twitter to get our articles delivered directly to your NewsFeed.
1Mahajan, N., & Wynn, K. (2012). Origins of “us” versus “them”: Prelinguistic infants prefer similar others. Cognition, 124, 227-233.
2Hamlin, JH. K., Mahajan, N., Liberman, Z., & Wynn, K. (in press). Not like me = bad: Infants prefer those who harm dissimilar others. Psychological Science.
Dr. Tim Loving – Science of Relationships articles | Website/CV
Dr. Loving’s research addresses the mental and physical health impact of relationship transitions (e.g., falling in love, breaking up) and the role friends and family serve as we adapt to these transitions. He’s a former Associate Editor of Personal Relationships and his research has been funded by the National Institute of Child Health and Human Development. 
