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of the convergence angle between the eyes to judge the object’s distance. You will be able to feel
your eyes converging if you slowly bring a finger closer to your nose while continuing to focus
on it. When you close one eye, you no longer feel the tension—convergence is a binocular depth
cue that requires both eyes to work.
The visual system also uses accommodation to help determine depth. As the lens changes its
curvature to focus on distant or close objects, information relayed from the muscles attached to
the lens helps us determine an object’s distance. Accommodation is only effective at short
viewing distances, however, so while it comes in handy when threading a needle or tying
shoelaces, it is far less effective when driving or playing sports.
Although the best cues to depth occur when both eyes work together, we are able to see depth
even with one eye closed. Monocular depth cues are depth cues that help us perceive depth using
only one eye (Sekuler & Blake, 2006).[13] Some of the most important are summarized in Table
4.2 "Monocular Depth Cues That Help Us Judge Depth at a Distance".
Table 4.2 Monocular Depth Cues That Help Us Judge Depth at a Distance
Name Description Example Image
Position
We tend to see objects
higher up in our field
of vision as farther
away.The fence posts at
right appear farther
away not only
because they become
smaller but also
because they appear
higher up in thepicture. (^)