TEMPESTUOUS relationships prove that the course of true love never has run smooth. Beatrice and Benedick battled over friends, Elizabeth and Mr Darcy over etiquette, and Punch and Judy over a baby (and sausages). But a study led by Brad Bushman of Ohio State University, just published in the Proceedings of the National Academy of Sciences, suggests that had these pugnacious partners eaten more, their aggressive tendencies might have been lower.

Dr Bushman looked at 107 heterosexual couples who had been married for 12 years on average, and searched for correlations between the levels of glucose in his volunteers’ bloodstreams and their affection (or lack of it) for their spouses. To do this, he and his team first asked that participants rate their spousal relations, to provide a baseline, and then monitored their blood sugar morning and evening for three weeks, while getting them to perform two revealing tasks.

The first, which each participant had to do every evening, was to stick pins in a doll he or she had been told represented his or her spouse. Up to 51 pins were available. The second, performed once, at the end of the experiment, was a computer game which participants were told they were playing against their spouses. (In fact, they were playing against the machine.) They were also told that if they won a round of this game, their prize was to be able to torment their partner with an unpleasant noise such as fingernails scratching a blackboard or the scream of an ambulance siren at a volume and duration of their choosing—and their choices were recorded.

Both tasks showed that blood-sugar levels do indeed help regulate marital annoyance. Most couples were not particularly punitive towards each other when it came to voodoo pin-sticking: the average number of pins stuck per night was 1.35, with the full 51 going in on only three occasions. But for any given individual the number of pins he or she (and women used more pins than men) stuck in the doll of an evening was correlated with his or her blood-sugar level that day. Similarly, those with low average blood-sugar levels over the three weeks of the experiment chose longer and louder punishment sounds for their spouses than those with high levels.

Blood-sugar levels and tolerance for one’s better half’s irritating foibles do, then, seem to be correlated. That does not prove causation—particularly in the case of the noise test, where higher or lower glucose levels over an extended period might be a reflection of something else significant and pertinent about the person in question. But it may be that one of the secrets of a successful marriage is to eat before you fight. If only the crocodile had not come along to consume Punch and Judy’s sausages, things might have turned out rather different.