Altruistic people are said to be "kind hearted" - and new research published in the journal Scientific Reports shows that generous people really are more in touch with their own hearts.
The study, carried out at Anglia Ruskin University and Stockholm University, is the first to find a possible physiological reason why some people are more charitable than others.
Participants were asked to take part in a computer-based game that involved repeated choices to share sums of money between themselves and another participant that they hadn't met.
Their choices affected how much real money they and the other participant received at the end of the study. The game has similarities to real-life charitable giving, in which recipients are not personally known to donors.
They also took part in a heartbeat detection task, which involved having their own heartbeat (ECG) recorded. The participants then listened, without feeling their pulse, to a series of sounds that were either in time or out of time with their heartbeats.
Those who were better at judging if the sounds were in time or not were better at detecting their internal body states. Performance on this task varied markedly between individuals.
The study found that participants' monetary generosity directly increases with their ability to detect their own heartbeat - those who were on average 10% better at detecting their heartbeat gave away an additional £5 to the other participants.
Dr Richard Piech, Senior Lecturer in Psychology at Anglia Ruskin University and co-author of the study, said: "Despite clear biological and economic advantages of acting in self-interest, people consistently make decisions that benefit others, at a cost to themselves. Our study suggests that selfless acts may be influenced by signals from the body that reach the brain."
Co-author Dr Jane Aspell, Senior Lecturer in Psychology at Anglia Ruskin University, added: "Our results showed an association between sensitivity to heartbeats and generosity, but more research is needed to understand why this relationship exists.
"It may be that an emotionally-charged situation - such as deciding whether or not to give money away - causes a change in heartbeat. This bodily change may then bias decision making towards the generous option in those people who are better at detecting their heartbeats. These findings suggest that, in some sense, people 'listen to their heart' to guide their selfless behaviours."