Children as young as age 3 will intervene on behalf of a victim, reacting as if victimized themselves, scientists have found.

With toys, cookies and puppets, Keith Jensen, a psychologist at the University of Manchester in England, and his colleagues tried to judge how much concern 3- and 5-year-olds had for others, and whether they had a sense of so-called restorative justice.

In one experiment, when one puppet took toys or cookies from another puppet, children responded by pulling a string that locked the objects in an inaccessible cave. When puppets took objects directly from the children themselves, they responded in the same way.

“The children treated these two violations equally,” said Dr. Jensen, a co-author of the study published in the journal Current Biology.