Optical illusions show vision in a new light

Mar 11, 2011

Optical illusions have fascinated humans throughout history. Greek builders used an optical illusion to ensure that that their columns appeared straight (they built them with a bulge) and we are all intrigued by the mental flip involved in the case of the young girl/old woman faces. New research published in BioMed Central's open access journal BMC Neuroscience demonstrates a more serious use of these illusions in understanding how the brain assesses relative size.

Researchers from University College London looked at two well known illusions: the Ebbinghaus illusion, where an object surrounded by small circles appears bigger than the same object surrounded by bigger circles, and the Ponzo illusion, where an object within converging lines (like train tracks or a corridor) is perceived to be larger than a same sized object nearer to the observer.

Their results show that the Ponzo illusion holds true regardless of which eye is used or whether the environmental clues are presented to a different eye than the objects. This suggests that our clues about relative size at a distance are determined after the two-dimensional images seen by the eyes have been processed into a single, three-dimensional, image. In contrast the Ebbinghaus does not work as well if the central object is presented to a different eye than the surrounding circles and shows that determination of an object's size relative to others in the same plane occurs before three-dimension processing.

Chen Song said, "Although our perception of size is distorted by environmental clues, this study shows that the extent of distortion and the brain mechanisms involved are dependent on the type of environmental contexts."

So while celebrity illusionists retain their ability to fool us, scientists can use these visual tricks to further our understanding of how we relate to the world around us – and have some fun at the same time!

Explore further: AAN: phenytoin neuroprotective in optic neuritis

More information: Interocular induction of illusory size perception, Chen Song, D. Samuel Schwarzkopf and Geraint Rees, BMC Neuroscience (in press)

Related Stories

Summer Moon Illusion

Jun 28, 2007

Sometimes you can't believe your eyes. This weekend is one of those times.

Hollow mask illusion fails to fool schizophrenia patients

Apr 06, 2009

Patients with schizophrenia are able to correctly see through an illusion known as the 'hollow mask' illusion, probably because their brain disconnects 'what the eyes see' from what 'the brain thinks it is seeing', according ...

Best Visual Illusion of the Year: How a Curveball Works

May 13, 2009

(PhysOrg.com) -- Visual illusions sometimes seem to have a magical element to them, but they're actually just the brain's way of interpreting reality. In an effort to promote public knowledge of cognitive ...

Recommended for you

AAN: phenytoin neuroprotective in optic neuritis

Apr 17, 2015

(HealthDay)—Phenytoin appears to be neuroprotective in acute optic neuritis (AON), according to a study scheduled to be presented at the annual meeting of the American Academy of Neurology, held from April ...

How a jab to the ribs jolts the brain into action

Apr 17, 2015

A short jab in the ribs instantly arouses a drowsy colleague during a long and dreary work meeting. A new study by Yale neurobiologists describes just what happens in the brain immediately following that ...

How do we hear time within sound?

Apr 16, 2015

How does our auditory system represent time within a sound? A new study published in PLOS Computational Biology investigates how temporal acoustic patterns can be represented by neural activity within audito ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.