The reason why you immeasurably care for a person without any thought of reward is one of science's biggest mysteries.
Now, Montreal University researchers claim to have unraveled the secret behind unconditional love.
The research team, led by Professor Mario Beauregard, of Montreal University's center for research into neurophysiology and cognition, found that the emotion emerges from a complex interplay between seven separate areas of the brain.
Such brain activity has only limited overlap with the cerebral impulses seen in romantic or sexual love, suggesting it should be seen as an entirely separate emotion.
"Unconditional love, extended to others without exception, is considered to be one of the highest expressions of spirituality. However, nothing has been known regarding its neural underpinnings until now," The Times quoted Mario, as saying.
To reach the conclusion, the volunteers were recruited on the basis that they had a proven ability to feel strong unconditional love: low-paid assistants looking after people with learning difficulties.
In the study, Mario asked them to evoke feelings of unconditional love and hold them in their minds while they had a magnetic resonance imaging (MRI) scan.
Of the seven brain areas that became active, three were similar to those of romantic love. The others were different, suggesting a separate kind of love.
The findings showed that some of the areas activated when experiencing unconditional love were also involved in releasing dopamine, a chemical deeply involved in sensing pleasure, with rising levels strongly linked to feelings of reward and even euphoria.
In a research paper in an academic journal, Mario said: "The rewarding nature of unconditional love facilitates the creation of strong emotional links. Such robust bonds may critically contribute to the survival of the human species."