3. PERCEPTION Flashcards
1
Q
Define perception
A
experiencing that results from stimulation of senses
2
Q
What are the properties of perception?
A
- Perception can change based on added information
- It involves a (often unconscious) process which is similar to reasoning or problem solving
- It also occurs in conjunction with actions- it is more than seeing or hearing, central to our ability to organize the actions that occur as we interact with our environment
3
Q
What does perception tell us about objects, and stimulus?
A
- The stimulus on the receptors are ambiguous:
- when u look at a paper, the image cast by the borders of the page on your retina is ambiguous
- the perceptual system is not concerned with determining an object’s image on the retina
- it starts with the image on the retina and
- its job is to determine what obj is ‘out there’ created by the image
- this is related to the inverse projection problem
- Objects can be hidden or blurred:
- people can often identity objects that are obscured -> incomplete/ blurry
- this occurs frequently in the environ
- but people know that part of an obj that is covered will continue to exist
- they are able to use their knowledge of the environ to determine what is present
- Objects look different from different viewpoints:
- this is related to Viewpoint Invariance
4
Q
Describe the Inverse Projection Problem
A
- task of determining the object responsible for a particular image on the retina
- as it involves starting with the retinal image
- and then extending rays out from the eye
5
Q
What is Viewpoint Invariance, and hence Viewpoint dependent theories?
A
Viewpoint Invariance theories:
- people’s ability to recognize an object
- even when it is seen from different viewpoints
- Biederman : object recog is not affected by observer’s viewpoint
Viewpoint Dependent theories:
- Tar & Bulthoff: changes in viewpoint reduce the speed/ accuracy of obj recog
- Milner & Goodale: brain has both visual processing systems
6
Q
What is Bottom-up processing and what theory is it related to?
A
Bottom up processing:
- looking at smth creates an image on the retina
- it starts at the bottom/ beginning of the system
- this is where environmental energy stimulates the receptors
- in this case, perception starts with the senses
It is related to Direct Perception Theories.
- perception comes from stimuli in the environment
- parts are identified and put tgt -> recognition occurs
7
Q
What is Top-down processing and what theory is it related to?
A
Top down theory:
- processing that originates in the brain
- starts from the top of the perceptual system
- it involves factors like the person’s knowledge of the environment
- also, expectations that people bring into the perceptual system
It is related to Constructive Perception theories.
- people actively construct perception using info based on expectations
8
Q
What are the two main conceptions of Object Perception?
A
- Helmholtz’s theory of unconscious inference
- TOP DOWN THEORY
- some of our perceptions are the result of unconscious assumptions we make abt the environ - Gestalt Principles of organization
- BOTTOM UP THEORY
- our overall experience can be understood by combining basic elements of experience called sensations
- perceptions can be explained by adding up small sensations
9
Q
What are the concepts involved in Helmholtz’s theory of Unconscious Inference?
A
- Likelihood principle
- we perceive the obj that is most likely to have caused the pattern of stimuli we have received
- the judgement of what is most likely to occur accord to this
- this happens through unconscious inference - Unconscious Inference
- our perceptions are the result of unconscious assumptions
- or inferences that we make about the environment
10
Q
Explain Helmholtz’s theory of Unconscious Inference in object perception.
A
HTOUI:
- some of our perceptions are the result of unconscious assumptions we make about the environment
- his qn was ‘how does the perceptual system decide that his pattern on the retina was created by overlapping rectangles?’
- his answer was based on the Likelihood Principle
- this happens through Unconscious Inference
- HENCE we infer that the pic on the left is a rect covering another rect because of past experiences we have had with them
- IMP: this process of perceiving what is most likely to have caused the pattern on the retina happens
rapidly and unconsciously - these unconscious assumptions are based on the likelihood principle
- which result in perception that seems instantaneous, even tho they r the outcome of a rapid process
11
Q
What are the concepts involved in Gestalt’s principles of Organization?
A
Apparent movement- illusion of movement created by stroboscope, as though movement is perceived, nothing is actually moving
- one light flashes on and off at the left side of screen
- there is a period of darkness for a fraction of second
- the second light flashes on and off on the right side
- the resulting perception is a light moving from left to right
- however this actually does not happen even though it seems like it did
HENCE
A. apparent movement cannot be explained by sensations
- as we saw, there is nth in the dark space betw flashing lights
B. the whole is different than the sum of the parts
- the perceptual system creates the perception of movement from stationary images
12
Q
Explain the Gestalt principles of organization, in object perception.
A
GPOO:
- perceptions can be explained by adding up small sensations
- intrinsic laws that are built into our syste
- the eg. of Apparent movement can explain how the whole is different than the sum of the parts
- this gave rise to some principles of perceptual org to explain the way elements are grouped together to create larger objects
- Good continuation
- points when connected, result in straight or smoothly curving lines
- these are seen to be belonging together
- lines tend to follow the smoothest path
- objs that are overlapped by other objs are perceived as continuing behind the overlapping obj - Pragnanz/ Principles of simplicity
- the law of pragnanz states that every stimulus pattern is seen in such a way that the resulting structure is simple as possible - Similarity
- similar things appear to be grouped tgt
- eg. columns of red circles vs alternating columns of red and blue circles - Closure
- tendency to see visual items as part of a larger obj - Figure Ground Segregation
- there is a figure and a background
- we are mostly able to see both alternately - Proximity
- how close elements are together
- the strongest proximity relationships are those between overlapping subjects
- but just grouping objects into a single area can also have a strong effect.
- the opposite is also true, by putting space between elements, you can add separation even when their other characteristics are the same.
13
Q
What are physical regularities and hence the oblique effect?
A
physical regularities:
- regularly occurring physical properties of the environment
- eg. there are more vertical and horizontal orientations in the environ than obliqued/ angled orientations
- this occurs in human made environments
oblique effect:
- it is therefore no coincidence that people can perceive horizontals and verticals more easily than other orientations
- eg. sand identations -> rounded moulds when pic is flipped -> we interpret light to come from above because that happens on earth
14
Q
What are Semantic regularities and hence Scene schemas?
A
Semantic regularities:
- characteristics that are associated with the functions carried out in different types of scenes
- semantics here refer to the meaning of a scene
- this meaning is often related to what happens within a scene
Scene schema:
- our visualisation contains info based on our knowledge of diff kinds of scenes
- and the expectations created by scene schemas, contribute to our ability to perceive objs and scenes
15
Q
Define Heuristics and hence Algorithms.
A
Heuristics:
- rule of thumbs
- provide the best guess solutions
- to a prob quickly and correctly
- gestalt laws are heuristics
Algorithms:
- procedure guaranteed to solve a prob
- it takes longer and is slow
- hence it shd produce a definite result
