As strange as it sounds, scientists think that it could. And that's not all: the infectious parasite carried by cats could also affect intelligence and has been linked to schizophrenia, and some studies suggest it can even raise your chances of being knocked down by a car.

But it's a little unfair to blame the humble moggy for all of the above. The parasite in question can infect all mammals, and, in Britain, the biggest risk of catching it is probably from eating an undercooked burger or bacon sandwich. Furthermore, given that at least a third of Brits are already unwitting carriers (rising to about 80% in France and Germany), the effects are clearly less pronounced than some press reports earlier this week may have led you to believe.

"We don't want people to go into a panic and think they're going to behave really strangely, because the problem is once we've got it we've got it for life," says Joanne Webster, a biologist at the University of Oxford who studies the parasite. "And in the vast majority, 99% of people or above, the results will be very subtle." For those that are interested, a simple blood test for antibodies raised against the parasite can tell you whether you're infected or not.

A relative of the malaria bug, the parasite is an intracellular protozoa called Toxoplasma gondii and its possible risks to unborn children have been known for some time - hence pregnant women are urged not to clean the cat litter tray, for example.

More recently, scientists have begun to unpick its effects on behaviour, discovering that infected rats lost their aversion to cats and so were more likely to be eaten, thus allowing the parasite to complete its life cycle. There are fewer experiments in humans, but results from studies of students and conscript soldiers in the Czech Republic in the mid-1990s highlighted the fact that infected people showed different personality traits to non-infected people - and that the differences depended on sex. Infected men were more likely to be aggressive, jealous and suspicious, while women became more outgoing and showed signs of higher intelligence.

Jaroslav Flegr, the professor of parasitology behind the research at Charles University in Prague, says he is baffled how these 1996 results made their way into the British press this week. He claims that his most important finding was in 2001 - and it showed, he says, that toxoplasma infection and subsequent delayed reaction times were linked to a greater risk of traffic accidents. "If our data are true then about a million people a year die just because they are infected with toxoplasma," Flegr says.

True or not, scientists are now trying to work out how the parasite might affect people's behaviour. In rats, the infection has been shown to affect the brain chemical dopamine, and new results from Flegr's laboratory seems to show a similar association in people.

Questionnaires designed to probe personality types, given to a thousand soldiers, found that those infected exhibited altered levels of novelty seeking, which, he says, is a common psychological marker for high dopamine levels.