leon barrett - university of california, berkeleycs182/sp08/sections/week05.pdf · status • a3p1...
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CS 182Sections 101 102Leon Barrett
Status
• A3P1 already due
• A3P2 due on Thursday
• This week– Color
– Representations and concepts
• Next week– Schemas and frames
Questions!
1. How do humans detect color biologically?
2. Are color names arbitrary? What are the findings surrounding this?
Questions!
• How do humans detect color biologically?
• Are color names arbitrary? What are the findings surrounding this?
A Tour of the Visual System
• two regions of interest:– retina
– LGN
http://www.iit.edu/~npr/DrJennifer/visual/retina.html
Rods and Cones in the Retina
The Microscopic View
What Rods and Cones Detect
Notice how they aren’t distributed evenly, and the rod is more sensitive to shorter wavelengths
Center / Surround• Strong activation in center, inhibition
on surround
• The effect you get using these center / surround cells is enhanced edges
top: the stimuli itself
middle: brightness of the stimuli
bottom: response of the retina
• You’ll see this idea get used in Regier’s model
http://wwwpsych.stanford.edu/~lera/psych115s/notes/lecture3/figures1.html
Color Opponent Cells
• These cells are found in the LGN
• Four color channels: Red, Green, Blue, Yellow
• R/G , B/Y pairs
• much like center/surround cells
• We can use these to determine the visual system’s fundamental hue responses
Mea
n Sp
ikes
/ Sec
Wavelength (mμ)
25
400 700
+RG
50
25
400 700
+GR
50
25
400 700
+YB
25
400 700
+BY
(Monkey brain)
Questions!
1. How do humans detect color biologically?
2. Are color names arbitrary? What are the findings surrounding this?
The WCS Color Chips
• Basic color terms:– Single word (not bluegreen)– Frequently used (not mauve)– Refers primarily to colors (not lime)– Applies to any object (not blonde)
FYI:English has 11 basic color terms
Results of Kay’s Color Study
If you group languages into the number of basic color terms they have, as the number of color terms increases, additional terms specify focal colors
B+W (Grey)
R+Y (Orange)
R + Bu (Purple)Bk or G or Bu
R+W (Pink)Y
Y+Bk (Brown)Y+Bk (Brown)R
BkBkBkW
BuBuBuBk
GGGG or BuBk
YYYYG or BuBk or G or Bu
RRRRR or YR or YBk or G or Bu
WWWWWWW or R or Y
VIIVIVIVIIIa / IIIbIIStage I
Representations
• What is a localist representation?
• What is a distributed representation?
• How many things can you represent with 4 neurons, in each representation?
• How many conjunctions of things can each represent?
• What is coarse coding?
• What is coarsefine coding?
Coarse Coding
info you can encode with one fine resolution unit = info you can with a few coarse resolution units
Now as long as we need fewer coarse units total, we’re good
CoarseFine Coding
but we can run into ghost “images”
Feature 2e.g. Direction of Motion
Feature 1e.g. Orientation
Y
X
G
G
YOrientation
XOrientation
YDir XDir
Coarse in F2, Fine in F1
Coarse in F1, Fine in F2
Categories
• What constitutes a basiclevel category? Is red a basiclevel category? Is maroon?
• Does it vary from person to person?
• What is a superordinate category? A subordinate category?
Categories & Prototypes: Overview
• Three ways of examining the categories we form:– relations between categories (e.g. basiclevel category)
– internal category structure (e.g. radial category)
– instances of category members (e.g. prototypes)
Furniture
Sofa Desk
leathersofa
fabricsofa
Lshapeddesk
Receptiondisk
BasicLevel Category
Superordinate
Subordinate
BasicLevel Category
• Perception: – similar overall perceived
shape
– single mental image
– (gestalt perception)
– fast identification
• Function: – general motor program
• Communication:
– shortest
– most commonly used
– contextually neutral
– first to be learned by children
– first to enter the lexicon
• Knowledge Organization:
– most attributes of category members stored at this level
What constitutes a basiclevel category? Definition:
Red? Maroon? yes arguable (expertise)
Category Structure
• Classical Category:– necessary and sufficient conditions
• Radial Category: – a central member branching out to lesscentral and noncentral cases
– degrees of membership, with extendable boundary
• Family Resemblance: – every family member looks like some other family member(s)
– there is no one property common across all members (e.g. polysemy)
• PrototypeBased Category
• EssentiallyContested Category (Gallie, 1956) (e.g. democracy)
• Adhoc Category (e.g. things you can fit inside a shopping bag)
Prototype• Cognitive reference point
– standards of comparison
• Social stereotypes
– snap judgments
– defines cultural expectations
– challengeable
• Typical case prototypes
– default expectation
– often used unconsciously in reasoning
• Ideal case / Nightmare case
– e.g. ideal vacation
– can be abstract
– may be neither typical nor stereotypical
• Paragons / Antiparagons
– an individual member that exhibits the ideal
• Salient examples
– e.g. 9/11 – terrorism act
• Generators
– central member + rules
– e.g. natural number = singledigit numbers + arithmetic
Mother• The birth model
The person who gives birth is the mother
• The genetic modelThe female who contributes the genetic material is the mother
• The nurturance modelThe female adult who nurtures and raises a child is the mother of the child
• The marital modelThe wife of the father is the mother
• The genealogical modelThe closest female ancestor is the mother (WFDT Ch.4, p.74, p.83)
Radial Structure of Mother
The radial structure of this category is defined with respect to the different models
CentralCase
Stepmother
Adoptivemother
Birthmother
NaturalmotherFoster
mother
Biologicalmother
Surrogatemother
Unwedmother
Geneticmother