Objects and scenes part 2 Flashcards
What is another example of bottom up processing?
Gist
What does RBC theory say about perceiving an object?
We build up small details to an overall object
What do experiments on scene perception suggest that indicate we see the gist of a scene?
We can perceive large scale properties first (<250 ms), and then more slowly fill in details (~500 ms) –> see gist first
How do we perceive gist?
Global image features that are holistically and rapidly perceived –> not built up from small bits
What are the 5 global image features we use to perceive gist?
Degree or naturalness
Degree of openness
Degree of roughness
Degree of expansion
Colour
What is degree of naturalness
Undulating contours (irregular) vs straight lines
What is degree of openness
Visible horizon line vs closed-in environment
What is degree of roughness?
Large even areas vs many small elements
What is degree of expansion?
convergence of lines of parallel lines
How do we perceive gist?
We simultaneously process visual scene at multiple spatial scales or frequencies
What do we process at low and high frequencies?
Low frequency = gist –> general trends
High frequencies = detail
What happens when you are shown a hybrid scene in low frequency?
you don’t notice the kitchen in the middle, just the gist
How does the hybrid image experiment work?
Low spatial frequencies –> Marilyn monroe
High spatial frequencies –> Einstein
Combine them
Normally information at low and high spatial frequencies is complementary but in a hybrid image it conflicts
Changing image size or viewing distance shifts the perceived balance
What is top down processing for perception?
Perception is not based purely on the stimulus
It also depends on experience, expectations, goals
Give an example of top down processing?
The numbers 12, 13, 14 and letters A, B, and C
The center symbol is the same but is influenced by context and our prior experience with the context
What do the upside down word examples show?
We reinterpret the same shapes based on context and prior experience
What does the dashed letters in words example show?
Version you saw is from your mind –> top-down
There are multiple possibilities
How does experience influence figure and ground perception? Give an example?
Meaningfulness/familiarity influencing figure/ ground separation –> based on experience
in two images:
1. Black area is more likely to be seen as figure because it looks like a lady
2. Black and white areas equally likely to be seen as figure in second image because it is flipped
Meaningful part is the figure. Not just based on concave/ convex
How does experience influence perceptual organization? Give an example
We have a tendency to perceive faces based on experience
Configuration of rocks looks like a face
How does experience effect object recognition? Give an example
all 4 images have the same blob in the picture but we interpret it differently based on experience
Provide the example that shows experience and scene perception.
First someone is shown the context scene (kitchen) then asked to identify a target object when it is flashed quickly
People show higher accuracy for context appropriate object
Person is better at identifying loaf of bread than a mailbox
Context we have been presented with first alters what we perceive first
What is a theory that explains experience and perception?
Helmholtz’s Theory of Unconscious Inference
What is the principle underlying Helmholtz’s Theory of Unconscious Inference?
Likelihood principle
What is Helmholtz’s Theory of Unconscious Inference?
Likelihood principle: we perceive objects most likely to have caused the pattern of stimuli we receive
Unconscious inference: The application of the likelihood principle is unconscious but based on past experience
