Infantile Justice

Infantile Justice Photo Credit: Clipart.com

Eight-month-old babies seem to favor rewarding good behavior and punishing bad.


Infantile justice.  I’m Bob Hirshon and this is Science Update.

It’s nice to see good rewarded and evil punished.  And apparently, even eight-month-old babies agree.  University of British Columbia psychologist Kiley Hamlin and her colleagues showed babies elephant puppets being either helpful or mean.  Later, the babies showed a preference not only for the nice elephants, but for other puppets that rewarded their good behavior.  Not so for the mean elephants.

Babies were choosing between someone who rewarded and punished a nice guy vs. someone who rewarded and punished a mean guy. And as adults, we would think that actually punishing the mean guy would be better. And that’s exactly what we found – that babies, by eight months, chose the guy who was mean to the mean puppet.

She notes that five-month-olds, on the other hand, favored puppets that were nice to anyone.  It’s not clear exactly how babies might use their sense of justice, but the fact that it exists so early suggests it’s deeply rooted in our consciousness.  I’m Bob Hirshon for AAAS, the Science Society.

Making Sense of the Research

To understand what this experiment demonstrated, it helps to know a little bit more about the study design.  First of all, it's based on the well-established principle that babies can show their interest by paying attention to things – in this case, reaching for a puppet first when presented with a choice of puppets.  Monitoring babies' attention, whether it's through behavior like this or simply tracking what they're looking at, is an important way that psychologists learn how babies perceive the world. 

In past experiments, Hamlin and her colleagues have shown a puppet show where one puppet (call him puppet A) has a goal, like opening a box.  Puppet B comes along and helps A open the box, while in another scene, puppet C gets in A's way, for example by sitting on the box.  Later, when given the choice of helpful puppet B or unhelpful puppet C, babies consistently reach first for B.  (The puppets are very similar except for a different color shirt, which changes in each run to make sure babies don't just prefer a certain color.)

This experiment added another level.  After a scene like the one above played out, two new puppets – let's call them 1 and 2 – are introduced.  These puppets either give a ball or take a ball away from puppet B or C.  So, you have scenes where a helpful puppet (B) is rewarded (with a ball), where the helpful puppet is punished (by taking the ball away), and where an unhelpful puppet is rewarded or punished.

When given a choice between puppet 1 or 2, the researchers found, not surprisingly, that eight-month-old babies prefer a puppet who was nice to a helpful puppet than one who punished a helpful puppet.  But the opposite was true when 1 or 2 interacted with a mean puppet.  There, they preferred the puppet who punished the bad guy to the one who rewarded him.

As you heard, this wasn't true of five-month-olds, who just liked nice puppets no matter what the circumstances.  The study shows that very early in development, babies start to develop a sense of what's fair and unfair, and what reward and punishment look like.  So we start acquiring a sense of justice long before it's generally applied to us.

Now try and answer these questions:

  1. How did the study evaluate babies' preferences for different kinds of behavior?
  2. What did this study examine that hadn't been explored before?
  3. The five-month-old subjects showed different preferences than the eight-month-olds.  What do you take from this?
  4. What does this study say about humans' sense of fairness?

You may want to check out the December 30, 2011, Science Update Podcast to hear further information about this Science Update and the other programs for that week. This podcast's topics include: Predicting drug side-effects before they can harm patients. A blood test for antidepressant effectiveness. Is 27 really an unlucky number for famous musicians? Are collecting and hoarding related? And why babies favor vigilante justice.

The Science Update Bouncing Babies delves into babies' perception of music.

In Musical Illusion, learn how babies' susceptibility to a musical trick depends on the language they learn.

For an interesting take on how adults perceive justice, see the Science Update Blaming The Hero.

Going Further

For Educators

The Science Update lesson Bouncing Babies delves into babies' perception of music.

In the lesson Musical Illusion, learn how babies' susceptibility to a musical trick depends on the language they learn.

For an interesting take on how adults perceive justice, see the Science Update lesson Blaming The Hero.

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