It's a truth universally acknowledged that we do strange things when we fall in love.
According to Hollywood, we may start traipsing up a fire escape clasping a bunch of roses between our teeth, or hot-legging it around a ship for a sweaty rendezvous on an abandoned car deck.
It's perhaps no surprise, therefore, to learn that being in love not only leaves us a hopeless bag of hormonal emotion - it also stimulates changes in our brain.
A pioneering new study has found that a brain of someone "in love" is markedly different to that of someone who is not.
Scientists from Southwest University in Chongqing, China, pieced together a "love map" to pinpoint the physical effects of falling for someone on the brain.
They pulled together 100 student volunteers and divided them into three groups; an "in-love" group, an "ended-love" group, who had recently ended loving relationships; and a "single" group, who had never been in love.
All three groups then underwent a brain MRI scan and were instructed not to think of anything when the scans were underway. The scans measured brain activity by detecting changes in blood flow.
The results indicated that up to 12 areas of the brain are involved in some way in the process of being in love.
Those from the "in love" category showed increased activity in several areas of the brain, including in areas that deal with reward, motivation, emotion regulation, and social interaction.
The amount of activity in some parts also positively correlated with the duration of love for the "in love" group.
For the "ended love" group, the longer they had been out of love, the lower the amount of activity detected in these areas of the brain.
And the "never been in love" group showcased the lowest level of activity of all in the same brain areas.
The results were published this month in the Frontiers in Human Neuroscience journal.
"Our study provides the first evidence of love-related alterations in the underlying architecture of the brain and the results shed new light on the mechanisms of romantic love," said Professor Xiaochu Zhang, leading the study.
He said the results may pave the way for "applying a resting-state fMRI approach" to test romantic love.
In other words, one day in the not-too-far-away future, scientists may be able to diagnose when someone's falling in love.
Hardly a poetic thought, but an interesting one nonetheless.