Three year olds become upset if their peers act in a selfish way
Photo: Adam McLane. Creative Commons. 

Three year olds get upset if their peers are selfish

By Child & Family Blog Editor and , | June 2017 

The response to selfish behavior was blame and emotion, a moral understanding - “Hey, what are you doing?”

A German study paired three-year-old children and invited them to play a game that produced a reward only if the two collaborated.

The researchers watched how the children reacted under three conditions:

  • One child intentionally “defected” from the collaborative activity and obtained a different, unshared reward – “selfishness”.
  • One child was not able to operate the game – “ignorance”.
  • The apparatus broke, preventing one child from playing the proper role – “accident”.

The reactions of the other child were very different in these three situations, all of which had the same result – the failure of the game.

The response to selfishness was blame and emotion, demonstrating a moral understanding that the other child was doing wrong – “Hey, what are you doing?”

The response to ignorance was more likely to be helpfulness – an attempt to teach the unknowing child how to play the game. As long as the partner appears willing to collaborate, three-year-olds don’t believe that, “ignorance is no excuse.” Rather, they have an intrinsic desire to help those in need.

The response to the apparatus breaking was much less emotional, with any blame directed at the apparatus itself, not the other child.

A team of researchers from the Max Planck Institute in Leipzig, Germany, and from Duke University in Durham, USA, worked with 72 boy-boy and girl-girl pairs of children.

The game was cleverly constructed. To obtain two marbles (one for each player), both partners had to pull on a rope together to move a block toward the two marbles. It was impossible to pulling on the rope alone or to access both ends of the rope, which made collaboration necessary. When two partners pulled together, the block moved and pushed the marbles from their platform, and the marbles rolled toward two separate openings where the players could retrieve them. The children could then insert their marbles into an opening in an elephant-shaped “jingle machine” behind the apparatus as a reward. The game was presented to them as “feeding the elephant”. Both ropes were not immediately accessible but had to be retrieved from the back of the apparatus by moving a detachable handle (with the rope magnetically attached to it) along a zigzag-shaped track. Only if both children moved their handles with the rope to the front could the joint pulling begin.


selfish test

Photo: Adam McLane. Creative Commons.

For the “selfish” condition, one child was taught to play the game differently – detaching the handle to open a box with a red sticker and a picture of an elephant. For this child, “feeding the elephant” meant putting the red sticker on the elephant picture. This left the other child stranded.

For the “ignorant” condition, one child was taught to pull the rope in a way that worked in training trials, but not in the actual game. The other child had been exposed to this “mistake” in practice trials, so had the knowledge to teach the “ignorant” child how to get it right.

The research sheds new light on how very young children perceive others’ intentions, and how important it is to them that others stay committed to obligations.

The study also further demonstrates three-year-olds’ sense of fairness in a collaborative situation, which has also been demonstrated in other earlier research. In one earlier experiment, also involving two three-year-olds collaborating for a joint reward, if one child unexpectedly received an earlier or bigger reward, the chances were that the lucky child would share the bounty with the unlucky one.


Kachel U, Svetlova M & Tomasello M (2017), Three-year-olds’ reactions to a partner’s failure to perform her role in a joint commitment, Child Development

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