Our
ability to perceive depth is quite remarkable considering our retina allows us
to see the environment around us in a two-dimensional image. We must expand our
view beyond single points in order to determine where objects are located in a
certain space. Researchers have studied the cue approach to depth perception.
Distance can be determined when one object partially covers another. The object
that is partially covered must be farther away than the object covering it.
But, when do we develop depth perception? Are we born with depth perception?
Researchers
wanted to find out if 6-14 month olds were able to perceive depth like adults.
Infants were put in the middle of a table with one side replaced by class so
that the ‘drop’ could be seen. The babies were then tempted over to the other
side by their mothers. Most of the infants would not even attempt to walk over
the glass, suggesting that they could perceive depth and saw the drop as dangerous.
Later, in 1973, a study done by Andrew Scwartz placed five and nine month olds
on each side of the ‘visual cliffs.’ These infants crawled over the glass as if
it were just a regular table. This is good indication that babies before the
age of 9 months do not have a sense of depth perception as the infants showed
no fear.
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The concept of depth perception in infants being the same as adults is interesting, because you would think the opposite. I assumed that depth perception was something developed over time, not just after six months of life. All the time we see parents worrying about their infants crawling into all kinds of dangerous trouble, like falling over things. I think these parents, because of the study you described above, may not know what kind of depth perception their infants are truly capable of, and they understandably underestimate them. This kind of "adult" depth perception in infants also makes sense evolutionary; in order to stay out of harm, babies must have adequate depth perception.
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