Gibson and Walk

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

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

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.

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

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.

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.

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? 9

Context: previous research RIGHT! Gibson and Walk thought the rats could have learned about depth in the course of the training and dismissed Lashley’s conclusion.

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) 

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.

Procedures How many infants were used? What were the other variations? (pg 111) 13

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

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?

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?

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.

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

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

Alternative Evidence Gibson and Walk’s 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?

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

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

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

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 Walk’s research.