"The study provides the first evidence that 3-year-olds can evaluate just how reasonable another person's distressed reaction is to a particular incident or situation, and this influences whether they are concerned enough to try to do something to help," said the study's lead author, Robert Hepach, of the Max Planck Institute for Evolutionary Anthropology.
The experiment involved 48 children, split evenly between girls and boys, from 36 to 39 months old.
Researchers recorded reactions of each child as he or she witnessed an adult acting upset in one of three contexts: when the distress was justified, when it was unjustified and when the cause of the distress was unknown.
In the study, two adults met with each child and engaged in various situations in which one of the adults would display distress by frowning, whimpering or pouting.
Their distress was in response to specific incidents of apparent physical harm, material loss or unfairness. In each case, the child witnessed the adult either experiencing something that should cause distress or reacting to something that occurred in a similar context but was much less serious.
Children who witnessed the adult being upset due to a real harm or injustice showed concern for him, intervened on his behalf and checked on him when he later expressed distress out of their view.
"These very young children really considered what was happening in a given situation rather than automatically responding with sympathy to another person apparently in distress," Hepach said in the statement.
The child's expression indicated she was "checking" when the incident did not warrant distress or the adult was out of sight but could be heard, the study said.
The study was published in the journal 'Developmental Psychology'.
