Visual Resolution and Eye Movements
When we look at scenes, we constantly move our eyes,
making saccades(eye movements) about 3 times per second. Most
vision researchers assume that we move our eyes in order to make up for
our poor visual resolution in the visual periphery. But what level of
resolution does the brain use to guide our eyes to new locations in the
periphery? An initial study (Loschky & McConkie, 2002) using a
gaze-contingent multi-resolutional display, found that there
is a threshold level of image resolution below which the eyes are less
likely to go an image region. This saccade-targeting thresholdvaries as
a function of both image resolution and distance from the center of
vision, such that with increasing eccentricity, image resolution
decrements must be greater to affect saccade targeting. A follow-up
study (Loschky, in preparation) found that the saccade-targeting
threshold is lower than the image blur detection threshold. Thus,
relatively low resolution information is useful for guiding the eyes in
natural scenes, but there are limits beyond which low-resolution
information loses its utility. We have argued that the brain uses a
neural competition among potential saccade targets in which removing
useful spatial frequencies reduces the saliency, or attractiveness, of
potential saccade targets, thus increasing the attractiveness of
closer, less filtered objects having useful information.
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