FLAT EARTH : Northern lights, Southern cross

American scientists at the Universities of Michigan and Illinois have discovered that there are two sorts of men. In a carefully controlled series of experiments comparing the behaviour of white men from the Northern US and whites from the South, they established that there are those - in this case the Southerners - who react to insults and aspersions on their honour with immediate massive surges of testosterone and stress- related hormones. And there are those - in this case the cool Northerners - who hardly take offence at all. The researchers - Richard Nisbett at Michigan and Dov Cohen from Illinois - do not suggest as much, but it is clear that if their line of research is pursued it could do much to help us to understand and even prevent many of the world's conflicts.

On the pretext of their taking part in another experiment students were asked to fill in a questionnaire and drop it off at a table at the far end of a corridor. On the way some were bumped and insulted by an angry student. Southerners showed a 12 per cent increase in testosterone levels, measured in their saliva, after the encounter, while Northerners showed no change. Levels of the stress-indicator cortisol shot up by 79 per cent in Southerners, double the rise in non-insulted students;the rise for Northerners was even less than the average for those who were not insulted.

The explanation for all this is that in the South there is a "culture of honour" which the North does not share. This culture demands that other people respect your strength, and suggests that if they do not, violence is justified. Southern men are not more fond of violence than Northerners. Rates of killings during burglary, for example, are the same. But rates of killings during arguments are higher. In matters of honour - if someone starts chatting up their girlfriend, say, or calls their manhood into question in some other way - they are much more likely to think violence appropriate.

One thinks of Orangemen marching down Catholic streets. One thinks of the disgusting cowardice behind the bombing of innocents. And one thinks of the only possible solution to a problem such as that in Ulster where two "cultures of honour" face each other. But after the Orangemen marched down Garvaghy Road, not even Cardinal Cahal Daly could bring himself to call on his flock to turn the other cheek.

Smoke without ire ...

This may be an illusion fostered by Brazilian flair in dance and football, but it is hard to imagine Brazilian men marching through an enemy neighbourhood in bowler hats - non-ironic bowler hats, at least - though I suppose they are as likely as anyone to respond to provocation with crass violence. Hard to put your finger on, I know, but the feel of a Rio carnival is somehow different from that of Ulster street gatherings. Something to do, perhaps, with the leaden weight of taking yourself far too seriously. The difference in cultures was borne out this week when the government introduced a law to ban smoking in public places. The law came into force on Tuesday. On Wednesday, it was universally ignored. Even the MPs were smoking in Brasilia's congressional chambers. "The law won't be applied in practice, as always in Brazil," said one psychologist puffing away in a Rio restaurant. Perhaps in some respects a "culture of anarchy" is healthier and more attractive than a culture of honour. At least the smokers and non-smokers didn't start bombing each other.