The Cyclops effect in adults: sighting without visual feedback.

When asked to look through a tube, younger children place it at the bridge of the nose, and not over one eye: the Cyclops effect. This is a natural response to a median plane egocenter. With maturity, the Cyclops effect disappears as we learn to overcome the consequences of an egocenter between the two eyes, and instead, to use the "preferred" eye. We videotaped adults (n = 14) and children with normal vision (n = 30), children with comitant strabismus (n = 14), and adults and children (n = 14) with one eye enucleated as they attempted to look through a plastic tube. Immediately in front of the face was a liquid crystal window that could be either transparent or opaque. As the tube was raised, the window was made opaque--blocking sight of the target, their hands, and the tube. Most binocular observers placed the tube approximately at the bridge of the nose. This was significantly different from the response of the enucleated observers who put the tube 75% of the way to the remaining eye (P = 0.0001). All observers align, on average, with the measured location of their egocenter when asked to perform a monocular task without visual cues. Deprived of visual feedback, binocular observers show the Cyclops effect, regardless of age.