Why Do Humans Have A Dominant Eye? An Evolutionary Biologist Explains

InnovationScienceWhy Do Humans Have A Dominant Eye? An Evolutionary Biologist ExplainsByScott Travers,Contributor.Forbes contributors publish independent expert analyses and insights. I write about biodiversity and the hidden quirks of the natural world.Follow AuthorMay 27, 2026, 08:30am EDTThe eye you instinctively close when you aim a camera has a biological explanation that spans hundreds of millions of years.gettyMost people discover their dominant eye by accident: lining up a shot, peering through a microscope or noticing that closing one eye rather than the other makes distant objects jump. Roughly two-thirds of humans have a dominant right eye, and most of the rest favor the left. A small fraction have no clear preference at all. What almost nobody asks, however, is why the asymmetry exists in the first place, and what it tells us about the brain that produces it. Here’s what we know, according to research.What Is The Purpose Of Our ‘Dominant Eye’?The short answer is that a perfectly balanced brain is, in evolutionary terms, a compromised one. Lateralization, or the division of cognitive labor between the left and right hemispheres, is not an imperfection in the design. It is the design. Peer-reviewed research across vertebrate species has consistently found that lateralized individuals outperform non-lateralized ones, because splitting functions between hemispheres avoids duplication, enables parallel processing and prevents competing neural responses from interfering with each other. A brain in which both sides handle everything equally is, paradoxically, doing less with more.Eye dominance is one of the most legible expressions of that asymmetry. A 2018 electrophysiological study tracking the speed of information transfer between hemispheres found that the dominant eye is a reliable predictor of which direction that transfer flows fastest, and that this pattern tracks closely with an individual’s overall lateralization profile. MORE FOR YOUIn right-handers...