Psya3 P - The Development Of Perceptual Abilities, Including Depth/distance, Visual Constancies

Front 1

Depth Perception and Visual Constancy
Definition

Back 1

Depth Perception (DP) is our ability to assess how far objects are from ourselves. Both monocular cues (e.g. motion parallax and occlusion) and binocular cues (e.g. retinal disparity) combine in helping achieve DP.

Visual Constancy is the abilty of an observer to perceive an object as having the same qualities, such as size, shape, colour, irrespective of the point from which they are viewing the object.

Front 2

Depth Perception
AO1 Key Feature 1
Description of Infant research - Gibson & Walk

Back 2

36 infants (6-14 months) were placed on the centre board of the visual cliff. All the infants were able to crawl (independent locomotion). Each child was then observed to see if it would crawl to the mother (cross onto the deep side) or if it would crawl onto the shallow side (away from the mother). 3/36 crossed onto the deep side, 27/36 moved onto the shallow side, 6/36 remained on the centreboard. G&W concluded infants had DP by the time they had independent locomotion.
So G&W tested NHAs that could walk from birth, e.g. chicks, and found that DP was also evident in these species since birth.

Front 3

Visual Constancy
AO1 Key Feature 1
Description of Infant research - Bower and Slater

Back 3

BOWER (1966) found that two month old infants were capable of shape constancy. Using operant conditioning, the infants were postively reinforced whenever they were shown a rectangle at 45 degree angle. When tested they still showed a preference for the rectangle (now presented at a different angle) over that of a trapezoid which cast the same retinal image of the original rectangle.

Front 4

Depth Perception & Visual Constancy
AO2 Criticism 1
Strengths & Weaknesses of using infants

Back 4

- Infants are unable to report what they can and can't see, therefore the development of techniques such as the visual cliff and habituation may be ingenious ways of getting around this issue, but they still rely on the researchers observing and interpreting the infants behaviour, which may be affected by researcher expectation and bias.
- Infants may also be susceptible to experimenter bias, Campos suggests the facial expressions of the mother may have dissuaded the infant from crossing on to the deep side of the visual cliff.

Front 5

Depth Perception & Visual Constancy
IDA Criticism
Nature vs. Nurture

Back 5

When using Infant studies to assess if perception is a feature of nature or nurture, most research tends to indicate many perceptual skills like DP and VC are present from birth. This therefore supports a more bottom-up way of processing and that indeed perception is innate. HOWEVER the visual acuity of an infant is incredibly poor and so it is unclear if any perceptual skills are purely the product of maturation or are a combination of both nature and nurture. Campos, for example, found two month olds could detect depth when placed on the deep side of the visual cliff (nature), but that they only developed a fear reaction of the deep side it when they were 9 months. Infant research suggests that nature may give us perceptual abilities, but that nurture is required for us to make best use of them.

Front 6

Depth Perception
AO1 Key Feature 1
Description of Cross-Cultural Studies - Hudson

Back 6

HUDSON (1960) showed pictures of a man pointing a spear at an elephant and antelope to European and Bantu children in South Africa. The pictures used visual cues, such as linear perspective and occlusion. At the start of Primary school, all the children had problems using the depth cues, however by the end of Primary School, nearly all of the European children were able to assess the pictures correctly, but many of the Bantu were unable to interpret the depth cues.

Front 7

Visual Constancy
AO1 Key Feature 1
Description of Cross-cultural Studies - Segall and Allpor t& Pettigrew

Back 7

SEGALL (1963) exposed American, European and Zulu individuals to the muller-lyer illusion. Segall found that the Zulu were much less likely to be affected by the illusion. He explained this because at the time the Zulu lived in circular huts and had therefore not had the experience of a 'carpentered world'.
ALLPORT & PETTIGREW - found that Zulu who lived in urban areas responded in a similar way to Europeans, whereas Zulu from rural areas were not affected by a trapezoid window illusion.

Front 8

Depth Perception & Visual Constancy
AO2 Criticism 1
Strengths & Weaknesses of using cross-cultural studies

Back 8

- The use of pictures and illusions e.g.the trapezoid window illusion may be an example of an 'imposed etic'. The Zulus' lack of ability to see the illusion may just mean that the illusion makes no sense to them NOT that they don't have shape constancy.
- It's unlikely individuals chosen are representative of their whole culture. Bruner noted that there are intra-cultural differences, like poverty, that affect perception. Therefore samples really need to reflect the diversity of each culture.
- CCR obviously uses natural experiments, as the culture in which you are raised is beyond the control of the researcher. So we cannot definitively say the difference in culture caused any differences in perceptual ability.
- Translation problems mean we can never be sure that cultural differences are not the product of variations in the meaning of the words used in questions. When Page (1970) slightly altered the wording of Hudson's question, the Zulu were able to perceive depth.

Front 9

Depth Perception & Visual Constancy
IDA Criticism
Nature vs. Nurture

Back 9

Most early CCR in the 1950s and 1960s suggested that experience affected perceptual abilities, supporting a more environmental explanation and nurture position. However, more recent research has found fewer cultural differences, possibly because more modern research does not have as many of the methodological flaws seen in earlier research.
It is also not right to assume that any cultural differences are purely the result of differences in environment. Berry (1971) reported that the pigmentation of the retina varies with the pigmentation of the skin. The high pigmentation of African people might explain why they were less likely to fall for illusions, as seen in Segall's research.

Front 10

Depth Perception & Visual Constancy
IDA Criticism
Non-Human Animal Research in assessing perceptual development

Back 10

Although NHAs have been used in perception research for some time, such as G&W's research. The use of NHAs has now really superseded both using infants and cross-cultural studies in assessing the development of perceptual abilities. Research such as Blakemore & Cooper and Hubel & Wiesel have concluded that innate visual mechanisms are shaped by experience, suggesting nature and nurture.
- However, should we really be generalising from the visual systems of cats to humans (our perception might be more affected by cognition)?
- Although most of the research may not be painful, some animals are left permanently perceptually impaired, so it might be unethical to use NHAs just to answer the nature/nurture debate.