CS 182Sections 103 - 104slides created Eva Mok (emok@icsi.berkeley.edu)Feb 22, 2006

(http://www.ritsumei.ac.jp/~akitaoka/color-e.html

Announcements

• a3 part 2 due tonight, Feb. 22nd, 11:59pm

• my office hours have moved to 2 Evans

• I have some of yr quizzes

Quick Recap

• Last Week

– Finished up backprop and neural networks

– Color: neurophysiology, psychophysics, etc.

• This Week

– Imaging techniques (fMRI, etc.)

– Categories & concepts

• Coming up– Image Schemas, Force-Dynamics

Quiz!

1. How do humans detect color biologically?

2. Are color names arbitrary? What are the findings surrounding this?

3. What constitutes a basic-level category? Is red a basic-level category? Is maroon?

4. Why does it take longer to determine whether “100 is close to 99” than “99 is close to 100”?

Quiz!

1. How do humans detect color biologically?

2. Are color names arbitrary? What are the findings surrounding this?

3. What constitutes a basic-level category? Is red a basic-level category? Is maroon?

4. Why does it take longer to determine whether “100 is close to 99” than “99 is close to 100”?

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://www-psych.stanford.edu/~lera/psych115s/notes/lecture3/figures1.html

How They Fire• No stimuli:

– both fire at base rate

• Stimuli in center:

– ON-center-OFF-surround fires rapidly

– OFF-center-ON-surround doesn’t fire

• Stimuli in surround:

– OFF-center-ON-surround fires rapidly

– ON-center-OFF-surround doesn’t fire

• Stimuli in both regions:

– both fire slowly

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 S

pike

s / S

ec

Wavelength (mμ)

25

400 700

+R-G

50

25

400 700

+G-R

50

25

400 700

+Y-B

25

400 700

+B-Y

(Monkey brain)

Quiz!

1. How do humans detect color biologically?

2. Are color names arbitrary? What are the findings surrounding this?

3. What constitutes a basic-level category? Is red a basic-level category? Is maroon?

4. Why does it take longer to determine whether “100 is close to 99” than “99 is close to 100”?

The WCS Color Chips

• Basic color terms:– Single word (not blue-green)– 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

Stage I II IIIa / IIIb IV V VI VII

W or R or Y W W W W W W

Bk or G or Bu R or Y R or Y R R R R

Bk or G or Bu G or Bu Y Y Y Y

Bk G or Bu G G G

Bk Bu Bu Bu

W Bk Bk Bk

R Y+Bk (Brown) Y+Bk (Brown)

Y R+W (Pink)

Bk or G or Bu R + Bu (Purple)

R+Y (Orange)

B+W (Grey)

Quiz!

1. How do humans detect color biologically?

2. Are color names arbitrary? What are the findings surrounding this?

3. What constitutes a basic-level category? Is red a basic-level category? Is maroon?

4. Why does it take longer to determine whether “100 is close to 99” than “99 is close to 100”?

Categories & Prototypes: Overview

• Three ways of examining the categories we form:

– relations between categories (e.g. basic-level category)

– internal category structure (e.g. radial category)

– instances of category members (e.g. prototypes)

Furniture

Sofa Desk

leathersofa

fabricsofa

L-shapeddesk

Receptiondisk

Basic-Level Category

Superordinate

Subordinate

Basic-Level 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 basic-level category?

Red? Maroon? yes arguable (expertise)

Quiz!

1. How do humans detect color biologically?

2. Are color names arbitrary? What are the findings surrounding this?

3. What constitute a basic-level category? Is red a basic-level category? Is maroon?

4. Why does it take longer to determine whether “100 is close to 99” than “99 is close to 100”?

Category Structure

• Classical Category:– necessary and sufficient conditions

• Radial Category: – a central member branching out to less-central and non-central

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)

• Prototype-Based Category

• Essentially-Contested Category (Gallie, 1956) (e.g. democracy)

• Ad-hoc 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 / Anti-paragons

– an individual member that exhibits the ideal

• Salient examples

– e.g. 9/11 – terrorism act

• Generators

– central member + rules

– e.g. natural number = single-digit numbers + arithmetic

Mother

• The birth modelThe 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

Marriage

• What is a marriage?

• What are the frames (or models) that go into defining a marriage?

• What are prototypes of marriage?

• What metaphors do we use to talk about marriages?

• Why is this a contested concept right now?

Language and Thought

• We know thought (our cognitive processes) constrains the way we learn and use language

• Does language also influence thought?

• Benjamin Whorf argues yes

• Psycholinguistics experiments have shown that linguistics categories influence thinking even in non-linguistics task

Language

Thought

cognitive processes