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.
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
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.