CS 182 Sections 103 - 104

CS 182Sections 103 - 104 slides 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! • How do humans detect color biologically? • Are color names arbitrary? What are the findings surrounding this? • What constitutes a basic-level category? Is red a basic-level category? Is maroon? • 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

Rods and Cones in the Retina http://www.iit.edu/~npr/DrJennifer/visual/retina.html

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

50 +R-G +Y-B 25 25 400 700 50 +G-R 400 700 25 25 +B-Y 400 700 400 700 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 Mean Spikes / Sec Wavelength (mμ) (Monkey brain)

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

Categories & Prototypes: Overview Furniture Superordinate • 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) Sofa Desk Basic-Level Category leathersofa fabricsofa L-shapeddesk Receptiondisk Subordinate

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 Basic-Level Category What constitutes a basic-level category? yes arguable (expertise) Red? Maroon?

Quiz! • How do humans detect color biologically? • Are color names arbitrary? What are the findings surrounding this? • What constitute a basic-level category? Is red a basic-level category? Is maroon? • 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)

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 Prototype

Mother • The birth model The person who gives birth is the mother • The genetic model The female who contributes the genetic material is the mother • The nurturance model The female adult who nurtures and raises a child is the mother of the child • The marital model The wife of the father is the mother • The genealogical model The closest female ancestor is the mother (WFDT Ch.4, p.74, p.83)

Radial Structure of Mother Geneticmother The radial structure of this category is defined with respect to the different models Stepmother Unwedmother Adoptivemother CentralCase Surrogatemother Birthmother Biologicalmother Naturalmother Fostermother

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

CS 182 Sections 103 - 104