When being a southpaw matters, medically.
Ten percent of the world is left handed, and it’s not always easy being in that elite group. Lefties struggle with notepads, scissors and can openers designed for righties, though there are special versions available. Left-handed people are also more likely to have allergies, migraines and be insomniacs. On the plus side, they make excellent baseball and tennis players. The point? There are fascinating differences in the right-handed and left-handed brain.
A new study from Cornell University has put forth an intriguing idea: that the location of a person’s neural patterns for their emotions are located in different places in their brains depending on whether they are left- or right-handed—and that this has serious implications for mental-health treatment.
Studies dating back for the past four decades suggest that the two hemispheres of the brain are each home to different sets of emotions. The theory is that emotions that engage with the world, such as happiness or anger, reside in the left side of the brain, while the parts that retreat, such as fear, live within the right. Daniel Casasanto, Ph.D. is an associate professor of human development and psychology at Cornell University. He has a new theory, called “sword and shield hypothesis,” which says that the way we use our hands determines how our emotions are organized in our minds. “Sword” refers to using your dominant hand to attack an enemy (engagement emotions) and “shield” is your non-dominant hand fending off an attack (avoidance emotions).
Casasanto’s work suggests that a current treatment for anxiety and depression, called neural therapy, could be damaging to left-handed patients. Neural therapy stimulates the left side of the brain using mild electricity or magnets, to boost life-affirming approach emotions. But “if you give left-handers the standard treatment, you’re probably going to make them worse,” Casasanto writes. “And because many people are neither strongly right- nor left-handed, the simulation won’t make any different for them, because their approach emotions are distributed across both hemispheres,” he said.
His work suggests strong righties, which make up about 50 percent of the population, should get the normal treatment. “Strong lefties should get the opposite treatment, and people in the middle shouldn’t get the treatment at all,” he wrote. However, Casasanto notes that his research studied only healthy participants and more work will be needed to extend the findings to a clinical setting.