A kiss is just a kiss - but when it comes to tongues, nothing compares with the effect of chocolate, a study has found.

Researchers who monitored the heads and hearts of romantically involved couples found they responded more to chocolate melting in their mouths than kissing.

Recordings of brain activity and heart rate were taken as the volunteers tasted pieces of dark chocolate or kissed their partners.

The findings showed that even the most passionate kisses fail to equal the "buzz" of chocolate.

"These results really surprised and intrigued us," said Sussex psychologist Dr David Lewis, who led the study.

"While we fully expected chocolate - especially dark chocolate - to increase heart rates due to the fact it contains some highly stimulating substances, both the length of this increase together with the powerful effects it had on the mind were something none of us had anticipated."

The 12 volunteers, all aged in their 20s, had electrodes attached to their scalps and were asked to wear heart monitors.

Each participant was told to place a piece of dark chocolate on the tongue and, without chewing, indicate when it started to melt.

For the second part of the experiment couples were invited to kiss each other in the same way as they would do normally.

Tests were carried out to record heart and brain activity without stimulation, activity when tasting chocolate, and activity when kissing.

The study found that at the point chocolate melts in the mouth, all regions of the brain receive a boost far more intense and longer lasting than the mental excitement from kissing.

Chocolate also made the heart beat faster. For some individuals, the number of beats per minute rose from a resting rate of about 60 to as high as 140. Kissing also set the heart pounding, but the effect did not last as long.

Dr Lewis, a former lecturer at the University of Sussex who runs a private research company called The Mind Lab, added: "There is no doubt that chocolate beats kissing hands down when it comes to providing a long-lasting body and brain buzz. A buzz that, in many cases, lasted four times as long as the most passionate kiss."

Although women are generally thought to be bigger chocolate fans than men, both sexes showed the same responses in the tests.

The research was conducted using a new Bournville chocolate from Cadbury called Deeply Dark which is soon to hit the shelves.

It is made from a 60% cocoa recipe similar to one used exclusively for the Royal Family since the days of Queen Victoria.

A spokeswoman for the chocolate makers said: "You'd think people would be shy about kissing in a laboratory, but that wasn't the case at all. We're not talking about a quick peck here."