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because our eyes are constantly moving, and one eye makes up for what the other eye misses.
But the visual system is also designed to deal with this problem if only one eye is open—the
visual cortex simply fills in the small hole in our vision with similar patterns from the
surrounding areas, and we never notice the difference. The ability of the visual system to cope
with the blind spot is another example of how sensation and perception work together to create
meaningful experience.
Figure 4.12 Blind Spot Demonstration
You can get an idea of the extent of your blind spot (the place where the optic nerve leaves the retina) by trying this
demonstration. Close your left eye and stare with your right eye at the cross in the diagram. You should be able to
see the elephant image to the right (don’t look at it, just notice that it is there). If you can’t see the elephant, move
closer or farther away until you can. Now slowly move so that you are closer to the image while you keep looking at
the cross. At one distance (probably a foot or so), the elephant will completely disappear from view because its
image has fallen on the blind spot.
Perception is created in part through the simultaneous action of thousands of
feature detector neurons—specialized neurons, located in the visual cortex, that respond to the
strength, angles, shapes, edges, and movements of a visual stimulus (Kelsey, 1997; Livingstone
& Hubel, 1988). [2] The feature detectors work in parallel, each performing a specialized
function. When faced with a red square, for instance, the parallel line feature detectors, the
horizontal line feature detectors, and the red color feature detectors all become activated. This
activation is then passed on to other parts of the visual cortex where other neurons compare the
information supplied by the feature detectors with images stored in memory. Suddenly, in a flash