If you saw a stamped, addressed letter on the ground, would you pick it up and post it? What if it was unstamped?

The answer might have a lot to do with where you live.

An Australian-first study has sought to examine whether there was a difference in the level of a person's altruism depending on their wealth and socioeconomic status.

Researchers at the University of Western Australia dropped 300 lost letters on the ground in 15 residential suburbs of varying socioeconomic status, and waited to see which ones made it back to the office.

Lead study author Cyril Grueter said the results found a strong link between socioeconomic status and the likelihood of someone returning the letter.

"I'm an evolutionary biologist, so I'm especially interested in behaviours that don't really make sense from an evolutionary point of view — such as unconditional altruism," Dr Grueter said.

"We wanted to explore this further by doing a very simple and powerful experiment.

"The study clearly tells us that people living in socioeconomically rich neighbourhoods are nicer, they are more altruistic than people living in poor neighbourhoods."

Wealthy western suburbs such as Dalkeith, City Beach and Nedlands topped the list, while Kwinana, Coolbellup and Medina had low return rates.

Crime rate may affect altruism

Peppermint Grove was also at the top, despite not having any post boxes in the area, and Dr Grueter said researchers still did not really understand the mechanisms behind the relationship between socioeconomic status and altruism.

"This is something we're trying to get to the bottom of, it could be that people living in a poor suburb just have other things on their priority list," he said.

"They have other problems to deal with, such as financial hardship or health concerns.

"People living in poor neighbourhoods experience higher levels of crime, and crime is really something that discourages the development of trust — and without trust you don't see altruistic behaviour, you don't see helping behaviour."

Out of the 300 letters — all of which had a birthday card inside — a total of 92 stamped and 42 unstamped were returned.

Originally it was believed that altruism was something that characterises humans across the board, but studies such as this have shown there are variations.

Dr Grueter said the research will not only be useful to sociologists.

"From a more applied perspective, those results could aid charities and other crowdfunded organisations in directing their efforts to where they will likely see the greatest return," he said.

"Data such as this provide a reflection of community attitudes and may therefore prove relevant to municipal government for policy development and intervention."