Discuss the development of perceptual abilities. Include examples from
infant and cross cultural studies in your answer (8...
Turnbull did a study into distance cues in Congo. He found a man called Kenge who had
spent his whole life in a very dense...
shapes, then results might be different. Due to the fact that the participants were infants and
have poor acuity and lack ...
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  1. 1. Discuss the development of perceptual abilities. Include examples from infant and cross cultural studies in your answer (8+16) The development of perceptual abilities is explained through whether the ability is innate, which would be nature, or whether they are learned, which would be nurture. Thus forming the nature vs nurture debate. There are 2 theories of perception: Gregory’s top down indirect theory and Gibson’s bottom up direct theory. The top down theory states that our mind generates expectations about what we are looking at and these expectations help us make sense of the mass information that reaches our eyes. The bottom-up theory states that our perceptions are based solely on data received at our eyes. Gibson and Walk devised the ‘Virtual Cliff. In this experiment they gathered 36, 6 month old infants, and put them on the devised apparatus. This was a sheet of glass which had a chequered pattern under half of it which made it look a lot deeper, creating a cliff effect; there being one ‘shallow’ side and one ‘deep’ side. The mothers encouraged their babies to crawl from the shallow side to the ‘deep’ side. The infants were fine on the ‘shallow’ side and perfectly content, however upon entering the ‘deep’ side they became very distressed. This suggests that the infants have used (monocular) depth cues. These are cues that can be represented in just two dimensions and observed with just one eye. Suggests they have the innate ability to use these cues.The findings led Gibson and Walk to come to the conclusion that depth perception is innate, which would support the nature argument- depth perception being there from birth. However there were many criticisms to the study. For example the sample size of 36 is very small meaning that the results cannot be generalised to the population. The fact that it was a lab experiment means that all the variable were controlled, thus meaning that the study lacks ecological validity and mundane realism- so it cannot be applied to the real word. For example the infants may have responded different if the study took place at their own home on one of the infants own tables that he/she is familiar with, they may have responded to different to what they did in the artificial environment. During this experiment the infants became very distressed; this creates some very strong ethical issues with the study concerning the welfare of the infants. It is likely that the infants had lots of other sensory experiences which would help with depth cues, meaning that the study cannot be conclusive as this would favour the nurture side of the debate, that the experiences and what they were exposed to let them to being able to have depth perception. Gibson and Walk’s study is supported by the work of Campos. He did a follow up study of the Virtual Cliff except made some changes. He obtained immobile infants, aged 2 months, and measured there heart rate (HR). It was found that on the ‘shallow’ side the HR was slower which suggests interest and calmness. However when on the ‘deep’ side the HR of the infants increased. This supports the idea that depth perception is innate, as an increase HR would lead to the conclusion of fear and anxiety. However, one problem with both Campos and Gibson and Walk’s studies is that infants have poor acuity, meaning they struggle to focus. Therefore this would make the results a lot less valid. As potentially the infants would not have known what they were seeing, or they could have potentially seen something else in the room they were scared about. For example the stranger to the baby that was in the room.
  2. 2. Turnbull did a study into distance cues in Congo. He found a man called Kenge who had spent his whole life in a very dense forest, meaning his perception and vision has never had to be stretched, everything is within close proximity in the forest. Turnbull took him out into the plains and pointed out some buffalos in the distance, to which Kenge replied ‘What insects are they?’ Kenge could not comprehend that they were buffalos. This suggests that distance perception comes from nurture, past experiences of distance cues enables them to interpret situations. This goes against the nature side of the debate. Although Kenge did laugh when he didn’t understand how things so small could be buffalos, it could have potentially distressed him at some point which would cause ethical issues. The fact that it was in Congo means that there would have been severe linguistic issues which meant that Turnbull could have misinterpreted what Kenge said. Due to the study being situated in Congo means that it is culturally biased and these sorts of findings cannot be applied to other cultures. This was a case study, which means that it was only tested on one person, and one person alone does not allow us to have data which can be generalised and applied to the population. The sample size is too small, the study would need to be done on more people for the results to be able to be generalised. As a whole case studies are also very time consuming and can be very costly. This study is very subjective as all the results are dependents on a man’s vision, for example Kenge may have had eye problems meaning that he couldn’t see long distance and Turnbull wouldn’t have known. This would have meant results were unreliable. In 1966 Bower created a study into visual constancies, in particular shape constancy. He used operant conditioning to habituate certain shapes to infants. He put pressure sensors on their head rest and when they looked at a certain shape they would get a reward. They were conditioned to respond to a rectangle at a 45oc angle, giving the retinal image of a trapezoid. They were then shown various objects, rectangle (same objective shape but different retinal image) and trapezoid (different objective shape but same retinal image). Findings showed that they responded to the rectangle each time, supporting the idea that shape constancy is learned-due to the infants choosing the objective shape as opposed to the retinal image. It supports the nurture side of the debate. The fact pressure sensors were used in the study gives some reliability in methodology but also means that there could have been errors in the equipment which could have give anomalous results. The study was done in a lab which means it lacks ecological validity and mundane realised as all the variables were controlled, so it cannot be applied to the real world. Bower could have done it without pressure sensors would have made the study less artificial and more realistic. The study was supported by Slater who did a study into visual constancy, in particular size constancy. He habituated the infants to different sized objects using operant conditioning and then placed 2 objects of different sizes side by side. One was further back than the other but gave the same retinal image. Infants responded to the unfamiliar shape as they recognised it was novel-displaying evidence of size constancy. This shows that visual constancies are learned which supports the nurture debate. Slater’s study lacks ecological validity and mundane realism as it is laboratory study, meaning results cannot be applied to the real world. For example the artificial environment in which the infants were in would never happen in real life, meaning it is an unfair judgement on the infants. If the study was performed at the child homes which his own
  3. 3. shapes, then results might be different. Due to the fact that the participants were infants and have poor acuity and lack the ability to completely focus we do not know whether they were really distinguishing between the retinal image and objective shape. This means is lacks validity as the study is difficult to conclude.

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