Infants already show signs that they want to help out adults without expecting anything in return, says a German study on altruism.

"The results were astonishing because these children are so young – they still wear diapers and are barely able to use language," said psychology researcher Felix Warneken of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, "But they already show helping behaviour."

As part of the study, Warneken developed scenarios in which an adult needed help. In one case, he dropped a clothespin on the floor while hanging up laundry.

Little fingers will lend a hand.

In 84 per cent of cases, infants as young as 18 months, who were not familiar with Warneken, would help retrieve the peg.

During the test, he never asked for help. He also did not thank or reward the child, since the study was designed to show if the toddlers could show altruistic behaviour.

When he deliberately threw a peg on the ground, the infants didn't help to retrieve it. That suggests the babies were able to infer when the peg was needed to complete the task of hanging up clothes.

Chimpanzees can recognize when they need to collaborate and choose the best collaborative partner, scientists say. (Courtesy: Max Planck Institute for Evolutionary Anthropology/Esther Herrmann)

So far, scientists say humans are the only species that can demonstrate altruistic behaviour.

Animals can help each other forage for food, hunt their prey or band together to protect themselves from predators.

But researchers don't consider such behaviour altruistic since each animal could simply want the same thing and they end up instinctively working together.

However, to see if chimpanzees could be as helpful as the toddlers, Warneken repeated the experiment on three and four-year-old chimps.

Chimps often did help retrieve an object dropped by a familiar human, but they weren't as eager to help as the toddlers were. And the primates' willingness to help didn't extend to more complicated tasks such as reaching into a box to get the object while some human toddlers did.

The study shows chimps can display helpfulness when they understand a person's goal, anthropologist Joan Silk of the University of California, Los Angeles said in a review accompanying the study in Friday's issue of the journal Science.

Researchers can't assume, however, that the subjects were motivated to help out of empathy, Silk said.