PERCEPTION KEY POINTS
Theories of perceptual organisation
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Perception is a complex activity and yet we manage to achieve it speedily,
accurately and without conscious effort.
Theories to explain perception have fallen broadly into two categories: top-down
(e.g. Gregory) and bottom-up (e.g. Gibson). It is almost certainly the case that
neither approach can adequately explain perception on its own.
We almost certainly use a mixture of bottom-up and top-down processing. When
viewing conditions are good and unambiguous , we can probably extract sufficient
information directly from the visual environment to form accurate perceptions.
However, in difficult conditions, when we are presented with degraded or
incomplete visual information, we need to use our experience and stored
knowledge to help us make perceptual sense.
Research in the field of visual perception has advanced considerably since Gibson
and Gregory first proposed their theories. Although both continue to be influential,
newer models e.g. Marr, have offered computational models of human perception,
while others, e.g. Milner and Goodale, have proposed a more complex two-system
model in which there is a distinction between vision for perception and vision for
action.
Development of perception
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The nature – nurture debate concerns the relative contribution of innate, biological
and external, environmental factors to our behaviour
The debate arose in the discipline of philosophy but has since been addressed by
psychologists who have considered it in several research contexts including that of
visual perception
At one extreme end of the debate, nativists believe that we are either born with
our perceptual abilities or that we develop them through a process of genetically
programmed maturation
At the other end of the debate, empiricists believe that humans develop
perceptual abilities through experience of their environment
Most contemporary psychologists believe that perceptual abilities depend on an
interaction of biological and environmental factors
Various methods have been used by psychologists to investigate the naturenurture debate in perception but they all have certain limitations.
Depth and distance perception are important for understanding the relationship
between objects in our visual world
We make use of a variety of cues to help us understand depth/distance
Some of these cues (primary) rely on biological mechanisms, while others
(secondary) appear to depend on some experience with the world
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Various ingenious techniques have been devised to investigate the development of
depth perception in human infants. Studies based on the visual cliff seem to
indicate that depth perception is innate, although there are some problems of
interpretation with this research.
Visual constancies allow us to maintain a stable visual world. Babies have been
shown to possess size and shape constancy from a very early age.
Cross-cultural studies have provided some interesting insights into visual
perception. However, they are often poorly controlled, have limited samples and
suffer from experimenter bias, so we must interpret the findings with caution
Many cross-cultural studies use pictures as the stimulus material so may reflect
lack of familiarity with Western art rather than limitations of perception in the real
world
Many of the studies are quite old now and. Although cross-cultural psychology is a
growing area, research into differences in visual perception is no longer a key
interest
Face recognition and visual agnosias
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Face recognition is a specialised form of pattern recognition
Face recognition is an important area of research because it has a number of
practical applications
We are generally better at dealing with familiar faces rather than unfamiliar faces
There is some debate as to whether face recognition is a highly specialised
mechanism or whether it is simply one type of complex processing
Computer models of face recognition can operate either feature by feature or
holistically. It is generally agreed that human face recognition is largely a holistic
process
Research using scrambled and inverted faces suggests that human face recognition
depends largely on holistic processing
One of the most influential models of face recognition was proposed by Bruce and
Young. This model contains a number of independent modules working in parallel
The model has been influential but only offers a limited explanation of face
recognition
Prosopagnosia is a relatively rare disorder in which individuals lose the ability to
recognise familiar faces
A number of case studies have been reported which provide clues about the face
recognition process in normal humans
Prosopagnosia research lends support to the Bruce and Young model