Is depth perception innate or learnt??

Notes from the SNAB course book

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Is depth perception innate or learned?
Cross-cultural studies
According to the carpentered world hypothesis, people who live in a world dominated by straight
lines and right angles tend to perceive depth cues differently from those who live in a circular culture.
Because we have grown up from an early age with these right angles we perceive slightly acute and
obtuse angles as right angles. People who live in circular cultures with few or no right angles are
rarely fooled by optical illusions because they do not see acute or obtuse angles as right angles.
Some researchers think that this is also genetic as well as an environmental factor. The genetic factor
being skin pigmentation. They link poor contour detection to higher retinal pigmentation.
Light-coloured people have low retinal pigmentation but contour detection is good so are likelier to
be caught out by illusions.
Depth cues in other pictures
Young children find it difficult to perceive 3D pictures, as they fail to interpret the depth cues in
pictures. But by age 11 they had overcome this problem and saw pictures in 3D. What is clear is that
depth cues are not innate but have to be learnt.
Studies with new born babies
New born babies are born with a number of characteristics like preferring sounds of humans and
recognising them and grasping. This suggests genes are involved in the wiring of the brain before
birth.
In an experiment babies were encouraged to crawl across a table that had a visual cliff. If depth
perception is innate they won't crawl across the table which is what happened in the experiment. The
babies were reluctant even when their mothers encouraged them. However this can only be done
with babies that can crawl (6 months old) and may have already learnt depth perception. Animals that
can walk as soon as they are born were tested and the same results showed.
Learning and memory
Learning occurs through our lives. For it to be effective you must be able to remember what you have
learnt. It is the changes to the synapses that underpin learning and memory.
Memory is distributed throughout the brain with different sites for short and long term memory. This
is demonstrated by looking at cases where people have lost the use of particular parts of the brain. A
patient, HM, suffered from serve epilepsy so doctors removed parts of his brain that seemed to
cause the problem. He immediately suffered amnesia. His long term memory before the operation
was unaffected but could no longer form new long-term memory but also found it difficult to
remember what he did a few minutes before. His memory to do everyday tasks was intact.
Memories can be created in two ways, by altering:
The pattern of connections
The strength of synapses

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Sea slugs and habituation
Eric Kandel won the noble prize for studying sea slugs to understand learning. The withdrawal of the
gill when the siphon is touched is a protective reflex like pulling your hand away from a hot flame.
Because they live in the sea they learn not to withdraw their gills every time a wave hits them.
Habituation is a type of learning.…read more

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