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'Crowding' makes sense of our peripheral vision

Although you may not realise it, an effect known as 'crowding' is allowing you to focus on each word in this sentence by blurring out everything else. Even though it affects 95% of the visual field, little is known about how crowding actually occurs. The phenomenon was thought...

Although you may not realise it, an effect known as 'crowding' is allowing you to focus on each word in this sentence by blurring out everything else. Even though it affects 95% of the visual field, little is known about how crowding actually occurs. The phenomenon was thought to make recognising things more difficult, but a team of UK and US scientists now asserts that crowding, a condition that originates from the brain and not the eye, is far from random. Findings from their study are published in Current Biology. Compared to our central vision, there are much fewer neurons at work in our peripheral visual field. This prompts the brain to draw attention to what is directly in front of us, reducing the emphasis on everything else outside that region of focus. For many of us with perfect vision, crowding is not a problem. For the millions that have lost their central vision because of macular degeneration, amblyopia ('lazy eye') and other eye diseases and conditions, the ability to recognise words or even people in front of them can become very difficult because they are forced to rely on the fuzziness of their peripheral visual field. Researchers from the University College London (UCL) in the UK and Harvard Medical School in the US believe that greater understanding of the mechanics behind crowding can help improve the visual experience for those who have incurred damage to their central vision, by improving the way objects are presented on TV and through the Internet, for instance. 'If we understand when crowding does and does not occur, then we could potentially create text and images that are less likely to cause crowding,' explained UCL's Dr John Greenwood. 'Similarly, if we can understand how things look when they are crowded, we could potentially generate text and images that could be recognised even when crowding has had an effect.' As part of their study, the team invited participants to look at a small area of random visual noise (similar to the noise we see when a TV signal is lost) from the corner of their eye and report back to the scientists when the area was surrounded by striped patches all oriented in a particular direction. The scientists determined that crowding makes things in front of us seem more regular by blending nearby objects together. To demonstrate the finding, the team used a photograph depicting a dramatic coastal village in Italy's Cinque Terre. Instead of using a normal reproduction of the scene, the researchers reassembled several patches throughout by swapping individual pixels within each region. When a viewer of the image focused on the centrally located brown house (the uncorrupted image), the 'noise' patches disappeared and the image appeared relatively undamaged. In their paper, they conclude that crowding can induce apparent structure where none exists. 'Though frequently characterized as a disruptive process through which object representations are suppressed or lost altogether, we demonstrate that crowding systematically changes the appearance of objects,' they write. 'We believe that this tendency of our brains to assume that the world is regular may have evolved because fewer cells in the brain are devoted to the edges of our vision compared to the centre,' added Dr Greenwood. 'In other words, the brain is not capable of delivering anything more than a simplified sketch using these resources.'

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United Kingdom, United States

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