Tiny eye motions help us find where Waldo is

Feb 20, 2009 by Lisa Zyga weblog
Waldo
Waldo, from the book series by Martin Handford, has helped to advance researchers' understanding of how the brain visually searches scenes.

(PhysOrg.com) -- To recognize faces in a crowd, the brain employs tiny eye movements called saccades and microsaccades to help us search for objects of interest. While researchers know that these movements are involuntary and vary in magnitude, they still do not fully understand how saccades and microsaccades work.

Now, a recent study by researchers at the Barrow Neurological Institute led by Susana Martinez-Conde has taken an important step toward understanding how the brain uses saccades and microsaccades in order to "sharpen" a scene. Previously, it has been unclear whether saccades and microsaccades have inherent differences or not. Here, the researchers found that both movements are likely generated by the same neural mechanism in the brain's strategy for optimal visual sampling.

In experiments, participants viewed various visual scenes ranging from blank images to complex pages of the Where's Waldo? books by Martin Handford. Then, the researchers measured the amount of saccades and microsaccades produced by the eyes when participants were either fixating on a specific point in an image or freely viewing the entire image.

Because microsaccades are operationally defined as movements that occur when fixating on a scene, the researchers looked for the same small magnitude of these movements when participants were freely viewing the scene. The researchers defined saccadic movements relative to microsaccades, with saccades having higher magnitudes than microsaccades.

The results showed that, when participants were freely viewing images, they produced more microsaccades when looking at the complex scenes than when viewing the blank and duller scenes. Specifically, more microsaccades occurred when participants were viewing an object of interest, such as when they found Waldo. Since participants stared longer at fixed points in the blank scenes than in the Waldo scenes, the increase in microsaccades could not be attributed to viewers fixating on Waldo for long times.

Instead, as the scientists explained, these results may support the proposal that microsaccades significantly re-sharpen an image and improve spatial resolution, as suggested in a recent study. While microsaccades occurred when participants viewed target objects, saccades occurred more often when participants freely viewed complex images as a whole. But rather than differentiating between microsaccades and saccades, the researchers suggested that both movements belong on a continuum of eye movements, which may together reflect an optimal sampling method by which the brain discretely acquires visual information.

The researchers hope that these findings may help understand the neural mechanisms underlying search behavior, both in the normal brain and in patients with eye movement deficits. In addition, understanding saccades and microsaccades could also help researchers design future neural prosthetics for patients with brain damage, as well as help to create intelligent machines that can see as well as humans.

More information: Otero-Millan, Jorge; Xoana Troncoso; Stephen Macknik; Ignacio Serrano-Pedraza; and Susana Martinez-Conde. "Saccades and microsaccades during visual fixation, exploration, and search: Foundations for a common saccadic generator." Journal of Vision, Volume 8, Number 14, Article 21, Pages 1-18, doi:10.1167/8.14.21

© 2009 PhysOrg.com

Explore further: US scientists make embryonic stem cells from adult skin

add to favorites email to friend print save as pdf

Related Stories

Volvo researches car tech to see if you are sleepy

Mar 19, 2014

(Phys.org) —Volvo Cars announced on Monday its work on a driver sensor system that can tell if the driver is alert, distracted, or even nodding off. The idea is to provide a safety system, where, on detection, ...

Big, fast, weird data

Apr 08, 2014

The "Big Data" research that continues to dominate IT agendas has traditionally focused on making sense of the growing volumes of computer data. Yet in recent years, the volume question has given way to the other V's of Big ...

Domain walls in nanowires cleverly set in motion

Apr 08, 2014

Researchers at Johannes Gutenberg University Mainz (JGU) have achieved a major breakthrough in the development of methods of information processing in nanomagnets. Using a new trick, they have been able to ...

Nature's extreme events provide immediate lessons

Apr 03, 2014

When the Canterbury earthquake of 2010-11 struck in the Christchurch area of New Zealand, wide spread liquefaction occurred, allowing the soil to behave more like a liquid. As a result of tectonic movements ...

Recommended for you

Leeches help save woman's ear after pit bull mauling

Apr 18, 2014

(HealthDay)—A pit bull attack in July 2013 left a 19-year-old woman with her left ear ripped from her head, leaving an open wound. After preserving the ear, the surgical team started with a reconnection ...

New pain relief targets discovered

Apr 17, 2014

Scientists have identified new pain relief targets that could be used to provide relief from chemotherapy-induced pain. BBSRC-funded researchers at King's College London made the discovery when researching ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

menkaur
not rated yet Feb 21, 2009
it's amazing, how complicated the workings of our minds are

More news stories

Low tolerance for pain? The reason may be in your genes

Researchers may have identified key genes linked to why some people have a higher tolerance for pain than others, according to a study released today that will be presented at the American Academy of Neurology's 66th Annual ...

How to keep your fitness goals on track

(HealthDay)—The New Year's resolutions many made to get fit have stalled by now. And one expert thinks that's because many people set their goals too high.

Cancer stem cells linked to drug resistance

Most drugs used to treat lung, breast and pancreatic cancers also promote drug-resistance and ultimately spur tumor growth. Researchers at the University of California, San Diego School of Medicine have discovered ...

Making graphene in your kitchen

Graphene has been touted as a wonder material—the world's thinnest substance, but super-strong. Now scientists say it is so easy to make you could produce some in your kitchen.

Easter morning delivery for space station

Space station astronauts got a special Easter treat: a cargo ship full of supplies. The shipment arrived Sunday morning via the SpaceX company's Dragon cargo capsule.