We don’t see only what meets the eye. The visual system constantly takes in ambiguous stimuli, weighs its options, and decides what it perceives. This normally happens effortlessly. Sometimes, however, an ambiguity is persistent, and the visual system waffles on which perception is right. Such instances interest scientists because they help us understand how the eyes and the brain make sense of what we see.
Most scientists believe rivalry occurs only when there’s “spatial conflict”—two objects striking the same place on the retina at the same time as our eyes move. But the retina isn’t the only filter or organizer of visual information. There’s also the “non-retinal reference frame”—objects such as mountains or chairs that locate things in space and make the world appear stable even when our eyes are moving.
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