Sleep and Perception: Perception Flashcards
What is bottom-up processing?
It is sensory driven; the processes that organise incoming information.
“Bottom-up processing refers to processing sensory information as it is coming in. In other words, if I flash a random picture on the screen, your eyes detect the features, your brain pieces it together, and you perceive a picture of an eagle. What you see is based only on the sensory information coming in.”
What is top-down processing?
Top-down processing, on the other hand, refers to perception that is driven by cognition. Your brain applies what it knows and what it expects to perceive and fills in the blanks, so to speak.
What are properties of the visual perception system?
- Adaption effects e.g. negative after-images. This does not require any higher order functions.
- Depth perception - Many cues are used to establish depth perception These include linear perspective, interposition, texture gradient, relative size and height in field.
What is binocular disparity? What are monocular cues?
Binocular disparity - the slight difference between the right and left retinal images. When both eyes focus on an object, the different position of the eyes produces a disparity of visual angle, and a slightly different image is received by each retina. The two images are automatically compared and, if sufficiently similar, are fused, providing an important cue to depth perception.
Monocular cues – reflect learning e.g. interposition (one block is overlapping the other and so it must be closer), texture gradient. Height-in field is another field to depth. Also, relative size give cues to indicate depth.
Learn very quickly that the world is made up of 2D cues that make up 3D perception.
What is a negative-after image?
Negative afterimages are caused when the eye’s photoreceptors, primarily known as rods and cones, adapt to overstimulation and lose sensitivity.The opponent color theory suggests that there are three opponent channels: red versus green, blue versus yellow, and black versus white. Responses to one color of an opponent channel are antagonistic to those of the other color. Therefore, a green image will produce a magenta afterimage. The green color fatigues the green photoreceptors, so they produce a weaker signal. Anything resulting in less green, is interpreted as its paired primary color, which is magenta, i.e. an equal mixture of red and blue.
What is Gestalt?
Whole percept - this describes the basic organisational tendencies in perception.
Perception systems requirement to make sense of anything – distinguish ground form sky. seeking meaningful groupings
e.g. proximity, similarity, continuity, closure
Looks at cues within the information see. Looks at things such as proximity. Similarities? Continuity? Closure?
Organisation: What is at the forefront of the image?
Perceptual constancies: Despite the fact the sensory information has changes, but your knowledge has not changed e.g. even though the door is now opened, the door is still the same
Perceptual illusions: Error made by the brain made by past experiences
“the perception of something objectively existing in such a way as to cause misinterpretation of its actual nature.”
What are sensory limitation?
Sensory limitations enables us to filter out irrelevant information. For example, sight is sensitive to a particular range if light waves. Auditor sensory apparatus is limited to a certain range of sounds.
What is selective attention?
Huxley says that we have adapted to be aware to parts of the environment that are useful to us. Without this we would be overwhelmed by the information.
There is a large relationship between perception and attention.
o selective attention – screening information
selective listening, inattentional blindness
effects of sensory loss (e.g. in the elderly) – vision and hearing is impaired. Some cognitive problems also arise e.g. problems in memory. This is due to them compensating for hearing loss – and so become less aware of other things that are going on. May mistake cognitive deficits but are instead a result of them compensating for sensory loss.
What is the internalised model?
We are carrying around our individual representation of the world and adding to it with every experience. What we experience from seeing is due largely to what we know rather than what we are seeing. What we experience is therefore not what is out there. The internal model is vital to our functioning. We therefore look without seeing. We make assumptions about what we are seeing based upon our internal model. We are constantly updating it and correcting it. Due to the internal model, the world remains stable even if you are moving. Your eyes move about 4 times a second and the internal model makes the assumption the world stays constant.
Who is SB?
At age 50, SB received a cornea transplant after having his sight removed by a virus at 10 months. SB once he recovered part of his sight, didn’t like what he saw. The world was dirty, it wasn’t as nice as he expected – he didn’t find his wife attractive. He fell into catastrophic depression.
When asked to draw an image of a bus, both after 6 months and 12 months, his images lacked 3 dimensionalities. He has not learnt about the 3D cues. He also didn’t draw the front of the bus, as he doesn’t perceive it. A blind person has never had any experience about the bus, never touch it. He was able to draw the other aspects as there is more sensory information. He may have touched other aspects.
Who is Mike May?
In 2003, three years after Mike May received a stem cell graft to one eye after losing it after chemical damage as a 2-year-old. May’s eye operation, the results were mixed. In terms of challenges, May reported being unable to grasp three-dimensional vision and to recognize members of his family by their faces alone.
