Posts archived in Perception
Many of you will be familiar with the video where two teams are throwing basketballs to each other and, in the middle of the match a man in a gorilla suit walks through the middle – but many people fail to notice because of a phenomenon called inattentional blindness. We often don’t see things that are obvious because our attention is elsewhere. If you haven’t seen the video look here or, a different example here
Drew and Wolfe recently conducted a study of inattentional blindness with radiologists. They were impressed by the skill shown by such professionals in their ability to detect significant shapes when starring at fuzzy images on an X-ray. It gave them an idea. Drew and Wolfe placed images of a man in a gorilla suit on a series of slides that radiologists typically look at when they’re searching for cancer. They found that 83 percent of the radiologists missed it! See here.
The original researchers, Chabris and Simons were originally inspired to conduct their research by a real life incident of a mistaken eye-witness account, see here.
Embed not working well – click the Youtube logo to watch it there – it’s worth it….
This week there was a programme on TV about The Boy who can’t forget (see here), about people who remember everything. They’re not the only ones with special recall. There are also people who don’t forget faces, they recognise anyone they have ever met (see Caroline Williams ‘Face savers’, New Scientist, September 15). It has been estimated that about 2% of the population have such super abilities for faces – about the same percentage as people who experience face blindness (prosopagnosia) which is the inability to recognise faces.
Research suggests that thesesuper recognisers don’t have especially superior memories nor are they better than average at object recognition. It appears they just have a special talent for recognising faces, which could be very useful in the police force. For example after the recent riots in London, police had to sift through thousands of fuzzy CCTV photos trying to recognise suspects. Super recognisers found it relatively easy to identify suspects in the CCTV footage.
The study of super recognisers can shed light on the way we process faces, and may even help understanding prosopagnosia. It seems that super recognisers use their brain differently, processing the whole face rather than individual components whereas the opposite is true for prosopagnosics. Studies using local and global letters are used to test this whole versus individual processing (see right). Participants are asked to read the large letter and end do this more slowly in the incongruent condition shown on the right. Prosopagnosics don’t show this slowing down, possibly because they don’t process at a global level (see page 43 of the A2 Complete Companion). Research is currently underway to see what happens when super recognisers try this task.
Interesting range of online experiments involving bio-motion here
It’s been known for ages that information on light levels is passed from the two retinas via a special small nerve from each eye to the SCN, but the mechanism of this is now more clear. As well as rods and cones, cells which are sensitive to light and give us black-and-white and colour vision there is a third type of light-sensitive retinal cell. These are far less in number than rods and cones, and react to light by expressing the pigment melanopsin, so they are known as mRGCs (melanopsin-expressing retinal ganglion cells). Not only do these cells send information to the SCN but they also control pupil size. And now it seems they also contribute to our visual image formation as axons from the mRGCs have been traced onwards from the SCN to visual processing centres. What does this imply? It gives some idea of how seriously sight impaired people can still detect levels of brightness, plus the possibility in the future of engineering melanopsin-expressing cells to improve or restore sight.
Fred Rieke, Timothy M. Brown, Carlos Gias, Megumi Hatori, Sheena R. Keding, Ma’ayan Semo, Peter J. Coffey, John Gigg, Hugh D. Piggins, Satchidananda Panda, Robert J. Lucas. Melanopsin Contributions to Irradiance Coding in the Thalamo-Cortical Visual System. PLoS Biology, 2010; 8 (12)
Nice article from the BBC on what we can learn about the brain from visual illusions. In the picture on the right you can’t see the panther about to attack – but you can when viewed in colour. Which explains why colour vision is adaptive.
Exergames are new video games based on using the Wii. They use physical activity not sight as input and have been developed for use in the fight against obesity. Now they have been adapted so that children with visual impairments can play them, important because these children as a result of sight problems do not find it easy to take healthy exercise and so are at a higher risk of obesity.
Research team leader Eelke Folmer says the modification that enables the games, such as tennis, to be played without visual feedback use audio and vibro-tactile feedback. Like standard Wii games these new ones can be played against other people or the computer. So far these games have been very successful in getting sight impaired people to exercise vigorously, though the sample sizes have been very small.
To play the VI Fit games, a user would need a Wii remote and a Windows PC with bluetooth support or a USB bluetooth dongle. The games can be downloaded using instructions at www.vifit.org. The games are not affiliated with or endorsed by Nintendo.
May 18, 2010 The death of Richard Gregory was announced on Monday of this week. He was an extremely well-known figure in Psychology, most notably for his work on visual illusions and his classic book Eye and Brain. His website has examples of some of his illusions. He also researched artificial intelligence, was an inventor with many patents to his name and founded the At-Bristol hands-on Science Museum, as well as appearing frequently on radio and TV.
I had the privilege of hearing him speak on several occasions and felt he had quite a magical ability to communicate enthusiasm and ideas.
Interesting footnote – Gregory was taught by Frederic Bartlett as an undergraduate and claimed Bartlett inspired him to take up psychology.
You know I keep thinking about the face on that cheese toastie that Jean Marc wrote about a while back. We seem to have an immensely strong urge to see faces everywhere: on the moon, in clouds, even in the most abstract of shapes and doodles. In our minds, the most random of patterns or stimuli seem to readily coalesce into two eyes a nose and a mouth. Every Read the rest of this entry »