You can never see it all at once

Popular Science - - HEAD TRIP -

TWELVE BLACK DOTS DANCE ABOUT this grid. They never ac­tu­ally move or van­ish, but no mat­ter how fast you twitch your eyes back and forth, you can’t seem to trap them all in your gaze at once.

Ninio’s ex­tinc­tion il­lu­sion is a riff on the Her­mann grid, a clas­sic piece of visual trick­ery in which your eyes see il­lu­sory gray blobs at the in­ter­sec­tions of a black-and­white lat­tice. We don’t know ex­actly why the Her­mann grid hap­pens, says Su­sana Martinez-Conde, a neu­ro­sci­en­tist at the State Univer­sity of New York’s Down­state Med­i­cal Cen­ter. This makes it chal­leng­ing to sort out the brain sci­ence be­hind any mod­i­fi­ca­tions on the orig­i­nal il­lu­sion.

Re­searchers’ pre­vail­ing the­ory for the flick­er­ing-dots vari­ant above is that we have more neu­rons clus­tered at the cen­ter of our vi­sion than the out­side. The lack of cells in our pe­riph­ery ren­ders us nearly blind to things far enough out­side the cen­ter. To com­pen­sate, the brain takes its best guess at what’s out there based on the more-vis­i­ble gray ar­eas. This makes a dot seem solid when we’re look­ing right at it but in­vis­i­ble when viewed with a side­ways glance.

So, when our eyes dart around the en­tire scene, the black dots move into and out of our visual field, mak­ing them seem as if they are flick­er­ing on and off. “Our visual sys­tem is lazy,” Martinez-Conde says. “Reg­u­lar pat­terns are tempt­ing be­cause you can look at a small por­tion and think you have the whole thing fig­ured out.” Don’t fret—we get by just fine with­out see­ing ev­ery­thing. Usu­ally.

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