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Feeling of seeing world in detail is illusory, scientists say

Oct. 20, 2014
Courtesy of Bielefeld University
and World Science staff

We usu­ally think we can see the world around us in sharp de­tail.

In real­ity, that’s only true for a ti­ny patch our field of vi­sion, sci­en­tists say—an ar­ea about the size of the thumb­nail of our out­stretched hand. The rest is blurred. But the brain fools us in­to think­ing oth­er­wise by us­ing mem­o­ry to fill in the blanks, a new study by two psy­chol­o­gists con­cludes.

“We be­lieve that we see the world un­iformly de­tailed,” said Ar­vid Her­wig of the Bie­le­feld Uni­vers­ity in Bie­le­feld, Ger­ma­ny, who in­ves­t­i­gated the is­sue with Wer­ner X. Schnei­der, al­so of the uni­vers­ity.

In reality, “we do not see the ac­tu­al world, but our pre­dic­tions” of how it would appear if we ex­am­ined each part in­di­vi­du­ally, Herwig said. The find­ings are pub­lished in the Jour­nal of Ex­pe­ri­men­tal Psy­chol­o­gy: Gen­er­al.

Only the cen­tral ar­ea of the reti­na—the light-sensitive tis­sue in the eye­ball—can pro­cess ob­jects in sharp de­tail, Her­wig said. That ar­ea is called the fo­vea, and it gives us a pre­cise view of an ar­ea the size of an out­stretched thumb­nail. All im­pres­sions we get out­side the fo­vea be­come pro­gres­sively coarse, Her­wig said.

Her­wig and Schnei­der hy­poth­e­sized that peo­ple learn through count­less eye move­ments over a life­time to con­nect the coarse im­pres­sions of ob­jects out­side the fo­vea to the de­tailed vis­u­al im­pres­sions af­ter the eye has moved to the ob­ject of in­ter­est. 

For ex­am­ple, the first time we see a foot­ball it may ap­pear as a blur­ry blob out of the cor­ner of our eye. But when we look at it di­rect­ly, a de­tailed im­age ap­pears. The brain then con­nects the two im­pres­sions—blur­ry and de­tailed. In fu­ture en­coun­ters with foot­balls, they ap­pear to us as pe­r­fect even be­fore we take a di­rect look: we fill in the mis­sing in­forma­t­ion from our col­lec­tion of stored im­ages.

The psy­chol­o­gists used eye-tracking ex­pe­ri­ments to test their idea. They meas­ured eye move­ments with a cam­era that records 1,000 im­ages per sec­ond. Par­ti­ci­pants in their study were giv­en ob­jects to look at, but un­be­knownst to them, some ob­jects were changed dur­ing eye move­ment. The aim was to cause the par­ti­ci­pants to learn new con­nections be­tween im­pres­sions from in­side and out­side the fo­ve­a—de­tailed and coarse im­pres­sions. That learn­ing in­deed hap­pened, ac­cord­ing to the in­ves­ti­ga­tors, and in just a few min­utes.


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We usually think we can see the world around us in sharp detail. In reality, that’s only true for a tiny patch our field of vision, scientists say—an area about the size of the thumbnail of our outstretched hand. The rest is blurred. But the brain fools us into thinking otherwise by using memory to fill in the blanks, a new study by two psychologists concludes. “We believe that we see the world uniformly detailed,” said Arvid Herwig of the Bielefeld University in Bielefeld, Germany, who investigated the issue with Werner X. Schneider, also of the university. Their findings are published in the Journal of Experimental Psychology: General. Really only the central area of the retina—the light-sensitive tissue in the eyeball—can process objects in sharp detail, Herwig said. That area is called the fovea, and it gives us a precise view of an area the size of an outstretched thumbnail. All impressions we get outside the fovea become progressively coarse, Herwig said. Herwig and Schneider hypothesized that people learn through countless eye movements over a lifetime to connect the coarse impressions of objects outside the fovea to the detailed visual impressions after the eye has moved to the object of interest. For example, the first time we see a football it may appear as a blurry blob out of the corner of our eye. But when we look at it directly, a detailed image appears. The brain then connects the two impressions—blurry and detailed. In future encounter with footballs, they appear to us as perfect even before we take a direct look: we fill in the missing information from our collection of stored images. The psychologists used eye-tracking experiments to test their approach. They measured eye movements with a camera that records 1,000 images per second. Participants in their study were given objects to look at, but unbeknownst to them, some objects were changed during eye movement. The aim was to cause the participants to learn new connections between impressions from inside and outside the fovea—detailed and coarse impressions. That learning indeed happened, according to the investigators, and in just a few minutes. Our brain in effect tells us not what we are seeing, but what it predicts we would see after a further eye movement, Herwig argued. “We do not see the actual world, but our predictions.”