If you're on social media, chances are you've seen or shared pleas for money for people involved in car accidents, suffering a personal tragedy, or fighting medical conditions.

In 2017, Australians doubled their rate of online donations to GoFundMe campaigns, stumping up more than $145 million across more than 70,000 campaigns.

Brisbane was the third-most generous location nationally, behind Melbourne in the top spot and Sydney in second.

After any car crash or tragedy, it's becoming increasingly common for a GoFundMe or other fundraising page to be launched by friends, family or even complete strangers motivated to do something.

In Brisbane alone, online fundraisers for tragic incidents such as the alleged murder of 16-year-old Larissa Beilby, the deaths of a young couple whose car rolled west of Brisbane and the family of six-year-old Indie Armstrong, who was killed in a Nambour car park, all amassed hundreds of donations from strangers, friends and family.

But what motivates people to donate to complete strangers?

University of Queensland researcher Cassandra Chapman is examining the psychology behind charitable giving, and said the answer was often the deep human experience of empathy.

She said there was very little academic literature into GoFundMe campaigns and peer-to-peer giving, but wider research indicated the influences of social networks suggested where the motivation for donating lay.

"In some ways online giving is different to donating to traditional charities," she said.

"The difference is that you’re often either asked for donations by someone you know, or you learn about the campaign through someone you know.

"My own research suggests that people pay more attention to these social network concerns when giving through peer-to-peer platforms.

"Therefore, there may be subtle concerns about reputation and perceived norms as extra levers to motivate giving."

Donations on peer-to-peer campaigns can often far exceed the original target, with the fundraiser for the Armstrong family's original $20,000 target reaching more than $79,000.

"The appeal of GoFundMe campaigns is likely to be psychologically similar to the appeal of any successful fundraising campaign: human empathy," she said.

"Decades of psychological research has established that we are motivated to give when we feel what someone else feels."

However, empathy "has its flaws".

Ms Chapman said empathy was by its nature a "spotlight", meaning we can only empathise with a few people at a time.

She said research by American psychologist Paul Bloom also noted people find it easier to empathise with people similar to themselves, and also that "empathy is innumerate".

"It’s impossible for us to feel a million times as bad about a million starving children as we feel about one starving child," she said.

Another American psychology researcher, Paul Slovic, found that people were less capable of empathising with a group, meaning more empathy was felt for one person than even for two.

In 2017 the American Red Cross reported their concerns of "donor fatigue" after three consecutive hurricanes blasted Texas, Florida Puerto Rico saw rapidly dropping levels of donations.

But while major national and international charities are still more than capable of fundraising hundreds of millions of dollars, local fundraisers are becoming increasingly popular.

"Campaigns on crowdfunding sites like GoFundMe usually present the story of an individual who is suffering," Ms Chapman said.

"Because we see them and we hear their story, it is easier to feel empathy for them. And when we feel empathy we are more likely to give."

Research from the Queensland University of Technology's Australian Centre for Philanthropy and Nonprofit Studies showed the non-profit sector was facing increasing challenges maintaining support in a "highly competitive funding environment".

The centre found that while peer-to-peer fundraising was "increasingly disrupting traditional philanthropy", technology-based donations weren't a major source of revenue for non-profit organisations.

The Australian Charities and Not-for-Profit Commission website warns donors to do their due dilligence before donating to crowdfunding campaigns.

Questions to ask included whether money would be refunded if donation targets weren't met, if the fundraiser had been responsive to queries on social media and other platforms, and if the fundraiser had run previous successful campaigns.