Flashcards in Perception Deck (23):
So.. what is perception?
Perception are experiences resulting from stimulation of the senses.
What is bottom-up processing?
Processing that begins with stimulation of the receptors is called bottom-up processing.
What is top-down processing?
Top-down processing is processing that depends on a person's prior knowledge or expectations.
In what way is bottom-up processing supported by evidence? You don't need to mention specific experiments.
We know that sensory receptors react to our environment and relays the information to the brain via neurons and their connections. We also know that processing of these signals become more specialised further up in the system, at least for domains such as vision and sound.
Mention a classic top-down phenomenon of vision.
Size-constancy: how we tend to perceive objects as remaining the same size even when they move to different distances. If perception of size was wholly a bottom-up process, we would perceive the objects as losing or gaining size.
Mention a classing top-down phenomenon of olfaction.
Robert Teghtsoonian and coworkers (1978) asked participants in a laboratory situation to rade the odor intensity of different odorants and found that their participants gave almost identical ratings for weak sniffs and for strong sniffs. Physically, a strong sniff will create a greater stimulation of the olfactory receptor neurons (ORNs). Teghtsoonian and coworkers concluded from this result that their participants were taking the strength of the sniff into account in making their ratings.
A lot of work was done to describe different top-down perceptual phenomena. Who and what?
The Gestalt psychologists in the early 1900s proposed a number of laws of perceptual organization that indicate how elements in the environment are organized or grouped together.
Are the laws of perceptual organization laws?
Although the Gestalt psychologists called their principles laws of perceptual organization, they fall short of being laws because they don't accurately predict what is in the environment. The fact that the Gestalt laws can sometimes lead to incorrect perceptions means that it is more accurate to call them heuristics - rules of thumb that provide a best-guess solution to a problem.
Perception is influenced by ...
our knowledge of regularities in the environment.
Modern perceptual psychologists have introduced the idea that perception is influenced by our knowledge of regularities in the environment - characteristics of the environment that occur frequently. We can distinguish between two types of regularities. Which?
1. Physical regularities
2. Semantic regularities.
What are physical regularities? Give an example.
Physical regularities are regularly occurring physical properties of the environment. For example, there are more vertical and horizontal orientations in the environment than oblique orientations. Modern perceptual psychologists believe that our knowledge of such regularities influence our perception.
What are semantic regularities. Give an example.
Semantic regularities are the characteristics associated with the functions carried out in different types of scenes. A demonstration of this would be to ask someone to picture a lion, and then asking whether they imagined more than just the lion (savannah, zoo, Africa). Modern perceptual psychologists believe that our knowledge of such regularities influence our perception.
What is the oblique effect?
The obligue effect (Appelle, 1972; Campbell et al., 1966; Orban et al., 1984) is the phenomenon where people perceive horizontals and verticals more easily than other orientations. This, coupled with the fact that there are more vertical and horizontal orientations in the environment, has been taken as evidence suggesting we use our knowledge of regularities in the environment when perceiving.
What is the light-from-above heuristic?
The light-from-above heuristic (Kleffner & Ramachandran, 1992) refers to our tendency to judge items' physical qualities based on how they are lit up. When doing this, we are more likely to think that the item is lit up from a light source coming from above - because most light in our environment comes from above. This observation suggests that we use our knowledge of regularities in the environment when perceiving.
Researchers have found many effects that indicate top-down processes interfering or guiding our perception. How did these top-down processes come to be?
We do not know, and it is probably individual for each observed phenomenon. This question is really asking whether these top-down effects are learned, or if they are genetic.
What research has been done on the learned aspect of perception?
Researchers have experimented on animals, rearing them in particular environments, and observing the outcome.
In researching the learned aspect of perception, researchers have experimented on animals. Mention a study.
Colin Blakemore and Graham Cooper (1970) found that rearing a kitten in an environment consisting only of verticals reshaped the kitten's visual cortex so it eventually contained neurons that responded mainly to verticals.
A lot of what the brain does is process information that is being perceived. Mention two famous pathways.
The ventral and dorsal streams.
The ventral stream goes from... to..., and is also called .... because ....
The ventral stream goes from the striate cortex and delivers visual information to the temporal lobes. It is also called the "what"-pathway because research indicates that the pathway is responsible for determining an object's identity.
The dorsal stream goes from... to..., and is also called .... because ....
The dorsal stream goes from the striate cortex and delivers visual information to the parietal lobe. It is also called the "where"-pathway because research indicates that the pathway is responsible for determining an object's location.
One of the first influential experiments on the dorsal and ventral stream properties was which experiment?
Ungerleider and Mishkin (1982) studied how removing part of a monkey's brain affected its ability to identify an object and to determine the object's location. They created two tasks that supposedly measured this function, removed the theorised ventral and dorsal stream, and found results that indicated the "what" and "where" distinction we know today.
The "what" and "where" streams were never tested on humans.
False. Milner and Goodale (1995) : Patient D.F. had suffered damage to her temporal lobe from carbon monoxide poisoning, and was unable to match the orientation of a card held in her hand to different orientations of a slot. She was, however, perfectly able to "mail" the card when asked, despite that requiring her to perform the task previously mentioned.