CHILDREN under the age of six are inherently self-centred because of their immature brains, say scientists.
The findings suggests misbehaving toddlers may simply be unable to consider the wishes of others -- including their exasperated parents.
Scientists believe the selfishness of young children is linked to a late-maturing brain region involved in self-control.
While this part of the brain is unformed, children struggle to rein in their selfish impulses.
The German research could influence educational strategies to promote social behaviour.
Psychologists at the Max-Planck Institute for Cognitive and Brain Sciences in Leipzig carried out behavioural and brain-imaging studies. The children were observed as they engaged in two "games" called the Dictator Game and the Ultimatum Game.
In the Dictator Game, each participant was asked to share a reward with another child who could only passively accept what was offered. In the Ultimatum Game, neither child received a reward if the recipient rejected the offer.
The aim was to see to what extent children thought strategically when considering their own interests.
Dr Nikolaus Steinbeis, who led the study, said: "We conclude that egoistic behaviour in younger children is not caused by a lack of understanding of right or wrong, but by the inability to implement behavioural control.
"We were interested in whether children would share more fairly if their counterparts could reject their offers, and to what extent strategic behaviour was dependent on age and brain development.
"We observed an age-related increase in strategic decision making between ages six to 13 years and showed that changes in bargaining behaviour were best accounted for by age-related differences in impulse-control abilities and underlying functional activity of the left dorsolateral prefrontal cortex, a late-maturing brain region linked with self control."
A total of 174 children aged around seven to 14 took part in the tests, which involved negotiating with monetary units that could be exchanged for gifts.