If you are left-handed or related to someone who is, then you stand a better chance of remembering where and when you read this article. So say psychology professor Stephen Christman of the University of Toledo and Ruth Propper of Merrimack College.
In two experiments, they found that people better remembered whether they had seen a word before if they were either related to left-handers or shown the word twice on different sides of the visual field, which stimulates both halves of the brain. Because lefties and their relatives seem to have larger corpus callosums, the bridges of neurons linking the brain's hemispheres, these results suggest that interaction between the two halves strengthens memory for events. "So left-handers probably do have a richer ability to recall their lives," Christman, himself a southpaw, says.
Previous studies had shown that semantic memoryremembering, say, that Mount Everest is the world's tallest mountainengages just one side of the brain, whereas episodic memoryremembering how you learned about Everestrequires activity in both. No one had ever tested the connection between handedness and types of memory before. These results, published in the October issue of Neuropsychology, may also explain why we can't remember events from early childhood: the corpus callosum doesn't fully develop until age four or five.
Left-handers, who make up 15 percent of the population, don't have a monopoly on memory, though. The experiments showed that semantic memory was stronger in those individuals with all right-handed relatives, or when words were presented to just one side of the visual field. Both groups also recognized words they had seen before with equal ease. Christman says it's possible to induce ersatz left-handedness by moving the eyes from side to side, which gets both sides of the brain going. His own research indicates that 30 seconds of such eye motion can improve episodic memory by up to 50 percent.