Your normally cheerful spouse has suddenly, and inexplicably, turned cranky and an otherwise pleasant day is fast becoming a scene from a horror movie. Sound familiar?
When you see those storm clouds gathering in your partner's eyes, you might do well to offer some carbohydrates, and fast. They might just be getting the "hangries".
That is the advice of researchers who examined the connection between low blood sugar levels and aggression in married couples.
The paper, which was published in PNAS, found that when blood glucose levels dropped, spouses were far more likely to stick pins into voodoo dolls representing their mates.
The authors argue that loss of self-control is a contributing factor to aggression between intimate partners, and that self-control is linked to nutrition.
"Self-control requires energy, and that energy is provided in part by glucose," wrote lead study author Brad Bushman, a professor at Ohio State University.
"Glucose is made from nutritious intake that becomes converted into neurotransmitters that provide energy for brain processes. Low glucose levels can undermine self-control because people have insufficient energy to overcome challenges and unwanted impulses," Bushman and his colleagues wrote.
The authors described those who lashed out aggressively due to hunger as being "hangry".
To test the theory, authors studied 107 married couples.
For three weeks, the spouses' glucose levels were checked in the morning, before breakfast, and in the evening, before bed. They were also asked to perform a unique task at the end of the day, and to record the results.
"To obtain daily measures of aggressive inclinations toward their partner, each participant received a voodoo doll along with 51 pins and was told: 'This doll represents your spouse. At the end of each day, insert between nil and 51 pins in the doll, depending how angry you are with your spouse," the authors wrote.
Then, at the end of 21 days, they played a "game" that was designed to measure aggressive behaviour.
"Participants were told that they would compete with their spouse to see who could press a button faster when a target square turned red on the computer, and that the winner on each trial could blast the loser with loud noise through headphones," authors wrote.
They were told the noises included recordings of fingernails on a chalkboard and an ambulance siren. A volume dial allowed the choice of between silence and a raucous 105 decibels. They could also adjust the duration of the punishment, they were told.
In reality, the game, and the punishments, were a sham.
Instead of competing against each other, the spouses were playing the computer in a rigged outcome. Also, they weren't blasting their partners' ears. Because they were seated in separate rooms, they could not tell it was all a ruse.
Nonetheless, lower glucose levels translated to more pins stuck in doll and longer, more intense noise, authors wrote.
"Results suggest that interventions designed to provide individuals with metabolic energy might foster more harmonious couple interactions," the authors concluded.