CS 182 Sections Leon Barrett

Transcription

1 CS 182 Sections Leon Barrett

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6 Status A3 P1 already due A3 P2 due on Thursday This week Color Representations and concepts Next week Schemas and frames

7 Questions! 1. How do humans detect color biologically? 2. Are color names arbitrary? What are the findings surrounding this?

8 Questions! How do humans detect color biologically? Are color names arbitrary? What are the findings surrounding this?

9 A Tour of the Visual System two regions of interest: retina LGN

10 Rods and Cones in the Retina

11 The Microscopic View

12 What Rods and Cones Detect Notice how they aren t distributed evenly, and the rod is more sensitive to shorter wavelengths

13 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 psych.stanford.edu/~lera/psych115s/notes/lecture3/figures1.html

14 Mean Spikes / Sec Color Opponent Cells R G +Y B These cells are found in the LGN Four color channels: Red, Green, Blue, Yellow R/G, B/Y pairs +G R We can use these to determine the visual system s fundamental hue responses +B Y 400 (Monkey brain) Wavelength (mμ) much like center/surround cells 700

15 Questions! 1. How do humans detect color biologically? 2. Are color names arbitrary? What are the findings surrounding this?

16 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

17 Results of Kay s Color Study 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 Bk Bk Bk Y+Bk (Brown) Y+Bk (Brown) W R Y R+W (Pink) Bk or G or Bu R + Bu (Purple) R+Y (Orange) B+W (Grey) 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

18 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 coarse fine coding?

19 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

20 Coarse Fine Coding Coarse in F2, Fine in F1 Feature 1 e.g. Orientation Y Orientation Y G X Orientation G X Coarse in F1, Fine in F2 Y Dir X Dir but we can run into ghost images Feature 2 e.g. Direction of Motion

21 Categories What constitutes a basic level category? Is red a basic level category? Is maroon? Does it vary from person to person? What is a superordinate category? A subordinate category?

22 Categories & Prototypes: Overview Furniture Sofa leather sofa fabric sofa Superordinate Desk L shaped desk Basic Level Category Reception disk Subordinate 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)

23 Basic Level Category What constitutes a basic level category? Definition: Perception: Communication: similar overall perceived shape shortest single mental image contextually neutral (gestalt perception) first to be learned by children fast identification first to enter the lexicon Function: most commonly used general motor program Red? yes Knowledge Organization: most attributes of category members stored at this level Maroon? arguable (expertise)

24 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)

25 Prototype Cognitive reference point e.g. ideal vacation standards of comparison can be abstract Social stereotypes may be neither typical nor stereotypical snap judgments defines cultural expectations challengeable often used unconsciously in reasoning Paragons / Anti paragons an individual member that exhibits the ideal Typical case prototypes default expectation Ideal case / Nightmare case Salient examples e.g. 9/11 terrorism act Generators central member + rules e.g. natural number = single digit numbers + arithmetic

26 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)

27 Radial Structure of Mother Unwed mother Surrogate mother Biological mother Genetic mother Stepmother Adoptive mother Central Case Foster mother Birth mother Natural mother The radial structure of this category is defined with respect to the different models