Perception Flashcards
Defining Perception?
Possible definitions:
– the act of becoming aware of something through our senses
– Pattern recognition: ability to detect meaningful patterns in the environment (faces, objects, etc.)
Why study perception?
Perception is not always equivalent to reality
Sometimes perceptual errors offer a clue to how visual cognitive processes work (such as optical illusions)
Understanding perception helps designers create user-friendly displays
Inverse Projection Problem?
Determining the object responsible for a particular image on the retina
Objects can be hidden or blurred
How do we got rom this 2 dimensional picture to the experience of 3 dimensions?
View Invariance?
If the primary visual cortex only gets a 2D map from one
angle, how do we know what an object looks like from other
angles?
How do we know what the bottom of a chair looks like from seeing it from another angle?
Size Constancy?
How do we know something is the same size at different
distances, since when it’s further away it is smaller on our retina?
Perceptual processes?
Bottom-up processing:
Basic elements come together until the mind reaches a higher level of understanding
Top-down processing
Prior knowledge or context are used to analyze incoming information to inform perception
Helmholtz’s Theory Of Unconscious Inference? and what principle?
Some of our perceptions are the result of unconscious assumptions we make about the environment
Likelihood principle-we perceive the world in the way that is “most likely”based on our past experiences (Top down inference using prior knowledge)
Gestalt Principles of Perceptual Organization - Similarity?
Elements that look similar will be perceived as part of the same form or group
Gestalt Principles of Perceptual Organization - Proximity?
Elements that are close together will be perceived as a coherent group
Gestalt Principles of Perceptual Organization - Closure?
Humans tend to enclose spaces by completing a contour and ignoring gaps in a picture
Gestalt Principles of Perceptual Organization - Common Fate?
If two or more objects are moving in the same direction and at the same speed, they will tend to be perceived as a group
Gestalt Principles of Perceptual Organization - Symmetry?
Images that are perceived as symmetrical are experienced as belonging together
Gestalt Principles of Perceptual Organization - Good Continuation?
People tend to connect elements in a way that makes the elements seem continuous or flowing in a particular direction
Bayesian Inference?
Our estimate of the probability of an outcome depends on…
Top-down perception using:
1. Prior probability (“prior”) of the outcome
2. How much the available evidence is consistent with the outcome (“likelihood”)
From eye to cortex? (4)
Eye -> Optic nerve -> Lateral Geniculate Nucleus -> Visual Cortex
What and Where Pathways?
Ventral Stream: What (Object recognition)
Primary auditory cortex
Dorsal Stream: Where/How (Movement and spatial relations)
Primary visual cortex
Inferotemporal Cortex (IT)?
- Front end of ventral stream
- Cells selective for object categories
- Some regions selective for faces
- “View invariant”
Object identification: 2D image to 3D objects? (Ventral Stream)
Common to many theories:
- Reconstruct representations (or structural descriptions) of objects
- Match them to some kind of temple
Bottom-up Processing for object identification?
Extract basic features from a stimulus and compare to known patterns of stimulus features stored in long-term memory
There are at many different descriptions of how we employ basic bottom-up processes
- Distinctive Features Theory
- Recognition by Components Theory
- Template-Matching Theory
- Prototype Theory
Distinctive Features Theory?
All complex perceptual stimuli are composed of distinctive and separable attribute called features
- Allow observers to distinguish one object/person form another
Pattern recognition is accomplished by mentally assessing the presence or absence of a checklist of curial features