New research debunks long-held theory about left-handed brains
For decades, scientists have puzzled over why the majority of left-handed people process language in the left hemisphere of their brains - just like their right-handed counterparts. Now, a new study from 探花社区 and Oslo University has challenged one of the most enduring explanations for this phenomenon.
A team led by Dr David Carey at the 探花社区 Imaging Unit, working in collaboration with Professor Ren茅 Westerhausen of Oslo University, set out to test the long-standing hypothesis that left-handers have greater structural connectivity between the two hemispheres of the brain, reflected in a larger corpus callosum - the bundle of nerve fibres linking the left and right hemispheres. Their study, published in Brain Research, analysed a large sample of left-handed individuals, examining both their hand dominance and brain organisation for language.
Surprisingly, their results found no evidence to support the theory. Neither left-handers as a whole nor those with left-hemispheric language dominance showed an increased corpus callosum volume compared to other groups. The findings effectively dismantle the idea that differences in brain structure can explain why 70% of left-handed individuals still rely on the left hemisphere for language processing.
Bottom row: Rene Westerhausen, Emma Karlsson, Leah Johnstone and David Carey
Dr Carey explained, 鈥淭hese intriguing results put to bed the idea that structural connectivity can account for the unusual pattern of brain dominance in left-handers. Instead, subtle differences in how the hemispheres communicate functionally might be at play, and this is too nuanced to be detected simply by looking at brain structures like the corpus callosum.鈥
Professor Westerhausen added, 鈥淲hether someone is left or right-handed doesn鈥檛 reshape the overall structure of the brain substantially; it is more in the fine-tuning. Two vinyl records may look nearly identical but will sound completely different when played. As brain scientists, we need to stop focusing solely on the shape of the 鈥榬ecords鈥 and start listening more carefully to the 鈥榤usic鈥. To truly understand handedness, we must explore how the two sides of the brain work together in real-time.鈥
The study鈥檚 authors suggest that future research should focus on functional connectivity - how different regions of the brain interact dynamically - rather than searching for anatomical differences in the corpus callosum. By using advanced imaging techniques, researchers may be able to uncover new explanations for this persistent neurological mystery.
The full study is available in Brain Research and can be accessed .