Brad Bushman, slightly famous as the author of Beauty is in the eye of the beer holder: People who think they are drunk also think they are attractive*, has published a new study entitled Low glucose relates to greater aggression in married couples, by Brad J. Bushman, C. Nathan DeWall, Richard S. Pond, Jr., and Michael Hanus, Proceedings of the National Academy of Sciences, epub April 2014. The authors explain:
“Intimate partner violence affects millions of people globally. One possible contributing factor is poor self-control. Self-control requires energy, part of which is provided by glucose. For 21 days, glucose levels were measured in 107 married couples. To measure aggressive impulses, each evening participants stuck between 0 and 51 pins into a voodoo doll that represented their spouse, depending how angry they were with their spouse. To measure aggression, participants competed against their spouse on a 25- trial task in which the winner blasted the loser with loud noise through headphones. As expected, the lower the level of glucose in the blood, the greater number of pins participants stuck into the voodoo doll, and the higher intensity and longer duration of noise participants set for their spouse.”
The researchers studied 107 married couples for three weeks. Each night, they measured their levels of the blood sugar glucose and asked each participant to stick pins in a voodoo doll representing his or her spouse. That indicated levels of aggression.
The researchers found that the lower the blood sugar levels, the more pins were pushed into the doll. In fact, people with the lowest scores pushed in twice as many pins as those with the highest blood sugar levels.
After the 21 days, the couples then took part in a lab experiment in which they competed with their spouse in a computer game - they had to see who could press a button fastest when a target square turned red.
The winner of each of the 25 trials was once again given an opportunity to express their aggression towards their partner.
This time, they were allowed to blast the losing spouse with up to 5 seconds of an extremely unpleasant noise up to 105 decibels loud. The noise was the combined sound of a smoke alarm, dentist's drill and fingernails scratching down a blackboard.
The researchers found people's average glucose level - calculated from the 21-day study - had an influence on what happened.
"People with low glucose gave their spouse louder and longer noise blasts," says Bushman.
He says the study controlled for relationship quality.
The study procedure also raised [an unusual] problem. Bushman had to handle a call from his credit card company, which wanted to make sure it was really he who had spent $5,000 to buy more than 200 voodoo dolls.
*SciAm article: Beauty is in the eye of the beer-holder