When it comes to relocating to the humid tropics, there is one pattern of behaviour that nearly all expats seem to fall into – one so clichéd you mightn’t think it warrants much attention. But for me and my friends it has grown to the point of distraction. In fact, it could now be classed as a force of distraction.

An Australian friend calls it ‘going troppo’.

The term might originate from Australia’s steamy Top End territory and has colonial connotations (of the ‘going native’ variety) and, more commonly, mental instability.

However my friend was referring to it as lust: an unquenchable sexual haze that overcomes unwitting visitors to the tropics.

Some claim that no foreigner is immune to this pervasive horniness. It clouds judgment and acute concentration enough to make me wonder: is this what it’s like to be a man?

It’s the kind of headiness that makes a person view the approach of dawn as nothing but a race against time to have sex. Or fall in love with the tuk tuk driver who picked them up from the airport. Or get turned on by the sound of wild, monsoonal rain.

It’s not just bare skin and cheap drinks that make cold-climate brains melt in the heat. Sexuality is indeed affected by the seasons and as I learned, while drinking hot coffee under a whirring fan with sexologist Aimee Barneaud, the brain will take its cues from innocent sensations and think it’s head over heels.

A study by the Medical University of Graz, Austria, showed that in sunny weather a boost of vitamin D increased testosterone  – the main sex hormone – and libido.

“In French, we have the same word for horny and hot – chaud,” Aimee says. “The language shows this feeling of heat is really linked to sexual desire. Sometimes we can interpret a feeling of heat coming from inside, rather than outside. So we feel we are horny but we are just hot.”

On top of this embarrassingly simple deception, warm bodies are just looser and appear more receptive to potential lovers. Which does nothing for the notion that it’s cold weather that drives people to huddle together under the bed covers.

“When you’re cold your body holds itself in, it is turned closer to oneself and when you’re hot your body is more open,” Aimee explains. “You have a different posture and you wear clothes differently... legs and arms will not be tucked close to your body. It’s not body language exactly, because it’s not conscious.

“In Summer, with more outdoor activities, your body is more acute (to sensations). For women, when they wear pretty clothes they feel they’re more sexy and more open to sex,” Aimee assures me.

Later that night I’m wading through the crowd at a casual outdoors bar.

Forget dripping sweat and feeling self-conscious, I decide. There are more instinctual forces at work. People simply look more at ease in their lighter, hot climate clothes and even if the body isn’t on show in explicit shorts and nipple-tight singlets, perhaps the suggestion of a body through thin fabrics is enough to stir the imagination.

This may all be a case for the Science of the Obvious, but a study conducted last summer in France (where else!) revealed something less so. The  survey confirmed that the hotter the weather, the more couples having sex, but it is also showed that people living in reliably rainy climes were less likely to turn troppo once the weather heated up.

However  - and this might solve my tropical rain question – sex did increase for those wet-weather dwellers during big storms.

So if the body is so easily tricked into arousal, what about the heart? Is it easier to fall in love? So far mine has not strayed from the cerebral cold-weather cues it’s used to, but I know others that have.

“This is my theory,” Aimee says. “I think our body is the boss. We are not really aware of the messages it sends us. We always try to interpret them and I think we are correct 85 per cent of the time - and then we make some mistakes.”