Gibson and Walk

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Gibson and Walk
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What is Depth perception

• The ability to comprehend that some objects are
  further away than others
• Binocular cues (pen test)
• Relative size
• Texture gradient
• Motion Parallax

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(No Transcript)
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Nature/Nurture

• How could we apply this to vision?
• Nature, nurture, both
• Nativists, empiricists, interactionists

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Context

• What is the nervous system?
• The brain and spinal cord make up the central
  nervous system. The peripheral nervous system are
  the nerves that lead from the spinal cord to the
  rest of the body. Both the CNS and PNS make up
  the nervous system.

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Context

• We are born with a complete nervous system, but
  it is not mature.
• Use the following words to complete the gaps in
  the paragraph
• Nativists, empiricists, interactionists

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Context

• Evolution
• Adaptation to environment. Traits are adaptive if
  they lead to increased survival and reproduction
• Human infants have limited mobility
• Many animals are precocial relatively mature and
  mobile from birth.

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Context

• If depth perception is innate, it would be
  apparent by the time a young animal is mobile.
• Adaptive A young animal which does not have this
  ability at this critical time is less likely to
  survive, and therefore an innate ability to
  perceive depth would be adaptive.

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Context previous research

• Lashley and Russell (1934) reared rats in
  darkness and found they could still jump the
  correct distance onto a platform. They suggested
  this shows depth perception is innate.
• How else could you explain this finding?

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Context previous research

• RIGHT!
• Gibson and Walk thought the rats could have
  learned about depth in the course of the training
  and dismissed Lashleys conclusion.

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Aims

• To investigate if depth perception is learned
  through experience or whether it is present from
  birth
• If depth perception is innate, then it should be
  apparent by the time infants are able to move
  independently.  
• Humans are not mobile until about 6 months old
  inconclusive results.
• A child who could perceive depth at 6 months may
  have always been able to do so (nativist), or may
  have learned to do so in the 6 months since birth
  (empiricist) 

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Aims

• Therefore they decided to also test the depth
  perception of a range of non-human animals.
• Kids (baby goats), lambs, rats, turtles, chicks,
  and kittens.
• As some of these animals can walk from birth.
  This would then provide more evidence about
  whether depth perception is innate.

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Procedures

• How many infants were used?
• What were the other variations? (pg 111)

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Results

• How many infants moved? (pg 112)
• How many chicks, kids and lambs move?
• Rats, kittens, turtles...?

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Conclusions

• Humans
• Most human infants can discriminate depth as soon
  as they can crawl. However, some of them backed
  of onto the deep side of the cliff, meaning that
  they should still not be left close to a cliff
  edge
• Nature or Nurture?

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Non human animals

• Generally, the findings from non-human animals
  fits with the life history and natural
  environment of the animal.
• How does this apply to each species?

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Conclusions

• It supports a nativist position as all of the
  evidence suggests that depth perception is
  adaptive. The animals have depth perception which
  is suitable for their environment and motor
  ability.
• All animals were able to perceive depth by the
  time they could walk, implying that it is innate.
  If it was learned, the animals may not have been
  able to properly judge depth.

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Conclusions

• Dark reared kittens visual input needed for
  maturation
• Depth perception is __________
• Motion parallax is innate, relative size may need
  to be learned.
• Main conclusion Quote from Gibson

adaptive
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Evaluate the methodology

• Usual Headings
• Methodology
• Validity
• Sampling
• Ethics
• Bullet point as many evaluation points as you can
  think of.

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Alternative Evidence

• Gibson and Walks study could only use infants
  that could move
• Schwartz et al (1973)
• Infants placed directly onto deep side. Heart
  rate measured
• 5 months no change in heart rate
• 9 months heart rate increased.
• What does this imply?
• Alternative explanation?

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Alternative Evidence

• Bower (1970)
• Infants shown two discs of different sizes. The
  baby was approached by both, but feared the one
  which was closer.
• Therefore, Infants as young as 6 days have depth
  perception

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Alternative Evidence

• Sorce (1985)
• Performed a variation on the visual cliff.
• Watch the video, and record what he did and
  found.

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Alternative Evidence

• Witherington et al (2005)
• Infants who were experienced at crawling but not
  walking showed less fear of the visual cliff than
  those who had started walking
• New learning has to take place when the world is
  viewed from a new perspective

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Alternative Evidence

• Find one more piece of research that you find
  interesting on pg 115. Summarise findings and
  conclusions
• Use three colours to highlight research that
  supports, contradicts, or develops Gibson and
  Walks research.