LAUSR

If you are looking for a card to celebrate an anniversary or St Valentine’s day, you may well come across a selection featuring the wellknown sentimental lines: ‘Two souls with but a single thought, two hearts that beat as one.’ These days the saying is probably best known from a song by the rock band U2 but in greeting cards and on the internet, it is usually attributed (wrongly) to the English romantic poet John Keats. Its true source is a play by the Victorian actress Maria Ann Lovell, called ‘Ingomar the Barbarian’, and adapted from the Austrian playwright Friedrich Halm. Both authors disappeared into obscurity, so it was presumably easier to give the credit to Keats. The lines appear in a song, as follows: ‘What love is, if thou wouldst be taught, Thy heart must teach alone, — Two souls with but a single thought, Two hearts that beat as one. And whence comes love? Like morning’s light, It comes without thy call. And how dies love? A spirit bright, Love never dies at all!' It is rather intriguing that two lines by a forgotten Victorian actress could have caught on so powerfully in the popular imagination. Could this be because there is some biological truth to it? When people are in love, do their hearts really synchronise? On principle, this seems unlikely. Heart rate is determined by many internal and external influences that strong passion could scarcely override. Even if Romeo and Juliet did have an occasional heartbeat in synch, a difference of a fraction of second in subsequent beats would soon lead their pulses to diverge. In literal terms, the idea of ‘two hearts that beat as one’ is probably a nonstarter. However, couples do affect each other’s physiology in more subtle ways. A large number of studies have looked into these. Although they do not confirm the saying, they shed interesting light on physiological coupling.