From BBC News:
Have you ever failed to notice a friend's radical new haircut? Or missed a road sign showing a change in the speed limit? This failure to notice what should be very apparent is something we unconsciously experience every day as our brains filter the barrage of visual information which we are flooded with. And apparently it has a name; it is called change blindness. Scientists at Queen Mary, University of London, have invented a unique spot-the-difference-style computer game in order to study it. Milan Verma, a scientist at Queen Mary, explains: “It's the phenomenon where seemingly striking or obvious changes are not noticed.” He and his colleagues are asking volunteers to play the game – which involves looking at a screen as it flashes between two images of the same scene.
“It flicks between a pre-change version and a post-change version of the scene,” Dr Verma explains. “The volunteers simply have to press the button and tell us exactly when they spot the change.” Trying out the game at Dr Verma's office, my initial reaction was self-satisfaction; I spotted the difference in the first scene – a picture of a butterfly with orange stripes on its wings – almost immediately. In the pre-change scene the colourful insect had two stripes – one on each wing, and on the post-change, there was just one. Easy. Next? But I was quickly reminded that I am just as “change blind” as the next person. As an image of an iceberg scene with five penguins on it flashed in front of me, I stared blankly, unable to see a difference. “I'll let you off – there is a lot going on in this image,” Dr Verma reassured me. “But it's quite a big change.” He had to give me a clue – directing me to the area of the image where the change occurred – before I realised that a whole chunk of iceberg was missing in the post-change image.