At the end of the 21 days, each person participated in a button-pressing game. Whoever pressed the button first was given the privilege of blasting the loser with some really unpleasant sounds (think dentist drills and chalkboard squeaks). The winner could pick both the decibel level and the duration of the sound blast, including no blast at all.
The participants thought they were competing with their spouses, who were not visible during the test. In reality, they were competing with a computer that made sure they lost 13 out of 25 trials and that they received a random sampling of the noise options.
The researchers found that when they accounted (as best they could) for marital and sexual satisfaction and for typical levels of aggression (some couples were routinely more aggressive toward each other than others), daily evening glucose levels did correlate with number of pins stuck in the voodoo dolls. In case you’re wondering, women tended to stick more pins than men.
In the noise-blast test, people with lower average evening glucose levels blasted what they thought were their spouses with louder and longer noise bursts.
There are a lot of possible things besides just low glucose levels that can make a person want to stick pins in his spouse or blast her with unpleasant noises. However, between other trials showing that people have less impulse control when they have low glucose levels and my own personal experiments with hunger and irritability, I find these results totally believable.