How your eyes deceive you
In this tilt illusion, the lines in the centre of the image appear tilted counterclockwise, but they are actually vertical.
(Medical Xpress) -- Researchers at the University of Sydney have thrown new light on the tricks the brain plays as it struggles to make sense of the visual and other sensory signals it constantly receives.
The research has implications for understanding how the brain interprets the world visually and how the brain itself works.
People rely on their eyes for most tasks - yet the information provided by our visual sensing system is often distorted, unreliable and subject to illusion.
In a just published article in Proceedings of the National Academy of Sciences, Dr Isabelle Mareschal and Professor Colin Clifford, from the University's School of Psychology and The Vision Centre, report a series of groundbreaking experiments tracing the origins of the tilt illusion to the cells of the primary visual cortex. This is where the first stage of vision processing takes place before the conscious mind takes over.
"We tend to regard what we see as the real world," said Dr Mareschal.
"In fact a lot of it is distortion, and it is occurring in the early processing of the brain, before consciousness takes over. Our work shows that the cells of the primary visual cortex create small distortions, which then pass on to the higher levels of the brain, to interpret as best it can."
A common example of this that is often exploited by artists and designers is known as the tilt illusion where perfectly vertical lines appear tilted because they are placed on an oriented background.
"We wanted to test at what level the illusion occurs in the brain, unconscious or conscious - and also to see if the higher brain is aware of the illusions it is receiving and how it tries to correct for them," she explains.
"The answer is that the brain seeks more contextual information from the background to try to work out the alignment of the object it is seeing."
The team subjected volunteers to a complex test in which they indicated the orientation of a vertical line, perceived as constantly tilting from side to side, against a fuzzy background that was also changing.
"These illusions happen very fast, perhaps in milliseconds," Dr Mareschal says. "And we found that even the higher brain cannot always correct for them, as it doesn't in fact know they are illusions."
This is one reason why people's eyes sometimes mislead them when looking at objects in their visual landscape.
Normally, Dr Mareschal explains, it doesn't matter all that much - but in the case of a person driving a car fast in traffic, an athlete performing complex acrobatic feats, a pilot landing an aircraft or other high-speed uses of sight, the illusion may be of vital importance by causing them to misinterpret the objects they 'see'.
The brain uses context, or background, to interpret a host of other visual signals besides the orientation of objects. For example, it uses context to tell colour, motion, texture and contrast. The research will help study how the brain understands these visual cues adding to our overall understanding of brain function.
More information: Research paper: www.pnas.org/conte… ull.pdf+html
Provided by University of Sydney
- Optical illusion reveals reflexes in the brain Dec 07, 2011 | not rated yet | 0
- How the brain's architecture makes our view of the world unique Dec 05, 2010 | not rated yet | 0
- Not just your imagination: The brain perceives optical illusions as real motion Feb 02, 2009 | not rated yet | 0
- Optical illusions show vision in a new light Mar 11, 2011 | not rated yet | 0
- Mechanism of 'blindsight' explored Oct 31, 2005 | not rated yet | 0
- Motion perception revisited: High Phi effect challenges established motion perception assumptions Apr 23, 2013 | 3 / 5 (2) | 2
- Anything you can do I can do better: Neuromolecular foundations of the superiority illusion (Update) Apr 02, 2013 | 4.5 / 5 (11) | 5
- The visual system as economist: Neural resource allocation in visual adaptation Mar 30, 2013 | 5 / 5 (2) | 9
- Separate lives: Neuronal and organismal lifespans decoupled Mar 27, 2013 | 4.9 / 5 (8) | 0
- Sizing things up: The evolutionary neurobiology of scale invariance Feb 28, 2013 | 4.8 / 5 (10) | 14
How can there be villous adenoma in colon, if there are no villi there
13 hours ago As title suggest. Thanks :smile:
How can there be a term called "intestinal metaplasia" of stomach
May 21, 2013 Hello everyone, Ok Stomach's normal epithelium is simple columnar, now in intestinal type of adenocarcinoma of stomach it undergoes "intestinal...
Pressure-volume curve: Elastic Recoil Pressure don't make sense
May 18, 2013 From pressure-volume curve of the lung and chest wall (attached photo), I don't understand why would the elastic recoil pressure of the lung is...
If you became brain-dead, would you want them to pull the plug?
May 17, 2013 I'd want the rest of me to stay alive. Sure it's a lousy way to live but it beats being all-the-way dead. Maybe if I make it 20 years they'll...
MRI bill question
May 15, 2013 Dear PFers, The hospital gave us a $12k bill for one MRI (head with contrast). The people I talked to at the hospital tell me that they do not...
Ratio of Hydrogen of Oxygen in Dessicated Animal Protein
May 13, 2013 As an experiment, for the past few months I've been consuming at least one portion of Jell-O or unflavored Knox gelatin per day. I'm 64, in very...
- More from Physics Forums - Medical Sciences
More news stories
(HealthDay)—Migraines and depression can each cause a great deal of suffering, but new research indicates the combination of the two may be linked to something else entirely—a smaller brain.
Neuroscience 4 hours ago | 5 / 5 (1) | 0 |
Moving objects attract greater attention – a fact exploited by video screens in public spaces and animated advertising banners on the Internet. For most animal species, moving objects also play a major ...
Neuroscience 7 hours ago | not rated yet | 0 |
It is known that signs of neurological disorders such as Alzheimer's and Huntington's disease can appear years before the disease becomes manifest; these signs take the form of subtle changes in the brain and behavior of ...
Neuroscience 7 hours ago | not rated yet | 0
Scientists have reversed behavioral and brain abnormalities in adult mice that resemble some features of schizophrenia by restoring normal expression to a suspect gene that is over-expressed in humans with ...
Neuroscience 9 hours ago | 5 / 5 (1) | 0 |
Researchers at Johns Hopkins have unraveled the molecular foundations of cocaine's effects on the brain, and identified a compound that blocks cravings for the drug in cocaine-addicted mice. The compound, already proven safe ...
Neuroscience 9 hours ago | not rated yet | 0 |
Swiss scientists reveal the mechanism responsible for aging hidden deep within mitochondria—and dramatically slow it down in worms by administering antibiotics to the young.
8 hours ago | 4.7 / 5 (3) | 0 |
Researchers from Queen Mary, University of London have led the largest sequencing study of human disease to date, investigating the genetic basis of six autoimmune diseases.
8 hours ago | not rated yet | 0 |
Until now, little was scientifically known about the human potential to cultivate compassion—the emotional state of caring for people who are suffering in a way that motivates altruistic behavior.
5 hours ago | 5 / 5 (1) | 2 |
A new approach for immunizing against influenza elicited a more potent immune response and broader protection than the currently licensed seasonal influenza vaccines when tested in mice and ferrets. The vaccine ...
5 hours ago | not rated yet | 0 |
(HealthDay)—Implementation of systematic monitoring for medication adherence will allow for identification of barriers to adherence and tailoring of interventions, according to a viewpoint piece published ...
3 hours ago | not rated yet | 0
In a series of lab experiments designed to unravel the workings of a key enzyme widely considered a possible trigger of rheumatoid arthritis, researchers at Johns Hopkins have found that in the most severe ...
7 hours ago | 5 / 5 (1) | 0 |