Researchers from the University of California conducted an altruism experiment involving 74 children with an average age of four years old.
They found that those from poorer families were more likely to display altruistic behaviour than children whose parents earned more money.
They also found that generosity may lead the poorer children to be healthier than the wealthier children later in life.
During the study, the researchers played with the children one by one and explained that they would earn tokens which they could trade for prizes at the end of their visit.
The researchers attached electrodes to each child’s torso to collect physiological data, including information about heart rate and the vagus nerve.
The vagus nerve connects the brain with other key organs and provides a measure of the body’s ability to regulate stress.
At the end of the session, the children were told that they could donate some or all of their tokens to ill children who weren't able to come to the lab.
The researchers found that children from wealthier families shared fewer tokens than the children from poorer families.
The data also revealed that those who donated the most had the highest vagal tone readings. The higher the vagal tone, the more calm one feels, leading to better overall health.
“We usually think of altruism as coming at a cost to the giver, but our findings suggest that when children forgo self-gain to help people who are less fortunate, they may get something back in the form of higher vagal tone,” lead researcher Jonas Miller said in a statement.
“It means we might be wired from a young age to derive a sense of safety from providing care for others.
"Our findings suggest that fostering altruistic tendencies might be one path to promoting better health and wellbeing for all children."
This isn't the first study to suggest family income has an impact on child development and health.
Earlier this year, researchers from Children's Hospital Los Angeles and Columbia University Medical Centre conducted a major experiment to find out why children from wealthier families statistically do better in school.
They found that children who grow up in higher income families appear to have larger brains than children who come from lower income families.
"We know that experiences in the environment impact the way the brain wires itself through childhood and adolescence," Dr Elizabeth Sowell told The Huffington Post at the time.
"If we could somehow enrich the environments of particularly the poorer children, we might be able to change that trajectory to equalise it, to some extent."