Ch 3 Day 2 Flashcards
Evidence that perception extrapolates beyond input (sensation)
Reversible/Bistable/Ambiguous figures
Why is perception difficult?
- Imput is ambiguous
Ex: The Inverse Projection Problem
-The same object looks
Perception and Action
- Moving around helps us disambiguate objects
- Constant coordination occurs in the brain as we perceive stimuli while also takin action toward them
Serial vs Parallel Processing
Serial Processing
- One step at a time Ex: Reasoning, planning, problem solving
- slow, effortful
- conscious
Parallel Processing
- Many steps at once Ex: Perception
- Fast, easy
-Automatic
The “Visual Pathways”
Dorsal -> the “where” pathway: occipital -> parietal
Ventral -> the “what” pathway: occipital -> temporal
Optic ataxia
can recognize objects, but can’t grab them
Visual Agnosia
can grab objects but can’t recognize them
Double dissociation
Parallel Processing -> Binding Problem
- Features processed separately
- How are they bound together?
Binding Problem
3 Possible Ways to solve the Binding Problem
- Spatial Position- The visual areas processing features like shape, color, and motion each know the spatial position of the object (receptive field)
- Neural synchrony- The visual areas processing features of the same object fire in a synchronous rhythm with each other
- Attention- Focusing attention on an object combines the features (Feature Integration Theory, ch. 4)
Theories of Object Perception
- Helmholtz Theory of Unconscious Inference
- Environmental Regularities
- Gestalt Principles
Helmholtz Theory of Unconscious Inference (1866)
Likelihood Principle- We perceive the object that is most likely to have caused the pattern of input
Inference- What’s “most likely” is based on past experience
Unconscious- Fast process, we’re not aware
-> Perceptual Constancy
Perceptual Constancy
Though images on our retina may vary, we perceive a given object as being the same (constant) in size, shape, or color when we assume that these differences in retinal image are the consequence of distance, viewpoint, or lighting, respectively
- Environmental Regularities
Idea: Perception is turned to common features of the world
Physical Regularity: More horizontal and vortical lines in the world than diagonal (trees, buildings)
Light usually comes from above (The Sun)
Psychological data “Oblique effect”
If we see dark on top and light below, it looks concave. If we see light on top and dark below, it looks convex.
Tachistoscope
Pre-computer device to sow stimuli for precise breif duration
- Environmental Regularities
Idea: Perception is tuned to common features of the world
Semantic regularities?
Scene schema- Knowledge of what a kind of scene typically contains. Schemes can guide perception
- Gestalt Principles of perceptual Organization
- How do we figure out what we’re seeing? It starts with grouping sensory input in meaningful ways
- “The whole is greater thant e sum of its parts”
-Visiual elements are automatically grouped together to create larger objects, vased on priniples (rules)
- These processes happen quickly and automatically )=(NOT CONSCIOUS), thought to be bottom-up (not based on experiene)… but?
-Expectations… learned during single lifetime…vs. across evolution
Gestalt Principles
tricks/assumptions for perceiving groups of objects
Proximity -Things that are close to each other appear to be grouped together
Similarity- Similar things appear to be grouped together
Connectedness- When lines or other properties connect things, they appear to be grouped together
Common Fate- grouped together move together
Good Continuation- We assume straight or curved continuous lines, rather than lines that abruptly change direction, or line segments that just happen to be aligned
- Bayesian Inference
Inverse Projection Problem
3D World -> 2D Image on retina -> 3D mental representation
-Problem: Impossible
Resolving Ambiguity: Depth Perception
Binocular disparity: Two eyes but different images… the closer an onjet is
Monocular Cues: Accommodation
-Haze (aerial perspective), elevation, interposition (occlusion), elevation, texture, linear perspective, familiar size
Ponzo Illusion!
