Week 3 Perceiving objects, scenes, and colour Flashcards
Why do some perceptual psychologists say “the whole differs from the sum of its parts?”
Our understanding of the world comes form bottom-up processing. The information we gather through top-down processing (memory, knowledge) changes how we view the raw data of the world. Thus, the final sum is MORE than the raw input because our unique experiences shape how we view the world.
How do “rules of thumb” help us in arriving at a perception of the environment?
Rules of thumb allow us to make quick judgements. Quick perceptual processing comes from fast assumptions.
How do we distinguish objects from their background?
Simple neurons, complex neurons, EDGES build objects in our cognition and distinguish backgrounds.
Why are even the most sophisticated computers unable to match a person’s ability to perceive objects?
due to the challenge of object perception
One reason why object perception is challenging is due to stimuli on receptors being ambiguous.
Identify the name of and describe this problem.
Inverse projection problem
- an image on the retina can be caused by an infinite number of objects
- no 3rd dimension on retina
- different objects producing similar retinal images (can’t distinguish) AND same objects producing different retinal images e.g. door looks different when open and closed. an example of whole is not sum of parts
Another reason why object perception is challenging is due to objects being hidden or blurred.
Describe this problem.
the environment contains many obstructions
Another reason why object perception is challenging is because objects look different at different angles/ viewpoints.
Identify the name of and describe this problem
Viewpoint invarience
The ability to recognise an object regardless of the viewpoint. This is difficult for computers to perform.
e.g. top-dow processing allows us to identify a face at different viewpoints
Discuss the historical beginning of Gestalt psychology.
- Structuralism (William Wundt, 1800s)
Perceptions are created by combining elements of sensations. Similar to transduction. - Structuralism couldn’t explain apparent movement/ illusory contours
- Gestalts psychology by Wertheimer, Koffka and Kohler (1920s) created from this weakness.
Perceptions are based on rules of thumb/ assumptions.
What were the weakness of structuralism?
Structuralism couldn’t explain apparent movement/ illusory contours
Describe the Gestalt approach
The whole differs from the sum of its parts.
– Perception is not built up from sensations, but is a result of perceptual organization.
What are the 8 principles of perceptual organisation?
Similarity Proximity Synchrony Common region Common fate Uniform connectedness Good continuation Pragnanz
Describe the principle of perceptual organisation: Similarity
similar things are grouped together
Describe the principle of perceptual organisation: Good continuation
— connected points resulting in straight or smooth curves belong together
– Lines are seen as following the smoothest path
Describe the principle of perceptual organisation: Proximity
things that are near to each other are grouped together
Describe the principle of perceptual organisation: Common region
elements in the same region tend to be grouped together
Describe the principle of perceptual organisation: Common region
elements in the same region tend to be grouped together
Describe the principle of perceptual organisation: Uniform connectedness
Connection regions of visual properties are perceived as single unit
Describe the principle of perceptual organisation: Synchrony
elements occurring at the same time are seen as belonging together
Describe the principle of perceptual organisation: Common fate
things moving in same direction are grouped together
Define figure-ground segregation
determining what part of environment is the figure so that it “stands out” from the background
What are the 4 properties of figure and ground
> The figure is more “thinglike” and more memorable than ground.
> The figure is seen in front of the ground.
> The ground is more uniform and extends behind figure.
> The contour separating figure from ground belongs to the figure (border ownership).
What are 5 characteristics of a figure?
- small elements
- placed in a lower part of displays
- units which are symmetrical
- having meaning/ memorable
- oriented in a vertical manner
What are physical regularities? (perceiving a scene)
regularly occurring physical properties.
Characteristics within an environment such as the openness of the sky and smoothness of landscape which occur frequently
What is the Oblique Effect?
People more easily perceive horizontal and vertical lines than others
What is Uniform Connectedness?
Elements are defined by areas of the same colour or texture
What is the Light-from-above heuristic?
Assumption that the source of light will come from above as this is what occurs in a natural environment
What are semantic regularities ?
characteristics associated with the functions of scenes not the physical properties of the environment
Study by Hollingworth (2005)
> Observers were presented with a scene either with or without a target object.
> They then saw the target followed by a blank screen and were asked where the object was in the scene or where they would expect it to be.
> Both groups could accurately predict where the object would be.
What is this research evidence for?
semantic regularities
Palmer experiment
– Observers saw a context scene, followed by a target picture, flashed briefly (almost subconsciously: see Priming Studies).
– Results showed that:
>Targets congruent with the context were identified 80% of the time .
>Targets that were incongruent were
only identified 40% of the time.
> most likely to identify the loaf of bread and not the drum because it fits within the scene of the kitchen
What is this research evidence for?
semantic regularities
Describe Helmholtz’s (1866/1911) Theory of Unconscious Inference
- Main Principle - perceptions are result of unconscious assumptions about the environment
- explains why stimuli can be interpreted in more than one way, but we tend to favour one.
– Likelihood principle - objects are perceived based on what is most likely to have caused the pattern
- linked to the idea that stimuli projected onto the retina is ambiguous (inverse projection problem)
What is Bayesian inference
Our estimates of a probability are determined by two factors:
1. the prior probability/ prior - (initial estimate of probability of an outcome)
- The likelihood of outcome- the extent to which the available evidence is consistent with the outcome.
