COGS 101A: Sensation and Perception, Schemes and Mind Maps of Chemistry

Download COGS 101A: Sensation and Perception and more Schemes and Mind Maps Chemistry in PDF only on Docsity!

COGS 101A: Sensation and Perception^1

Virginia R. de Sa

Department of Cognitive Science

UCSD

Lecture 7:

Color (Chapter 6)

Course Information^2

• Class web page: http://cogsci.ucsd.edu/ desa/101a/index.html
• Professor: Virginia de Sa

? I’m usually in Chemistry Research Building (CRB) 214 (also office in CSB

? Office Hours: Monday 5-6pm ? email: desa at ucsd ? Research: Perception and Learning in Humans and Machines

Course Goals^4

• To appreciate the difficulty of sensory perception
• To learn about sensory perception at several levels of analysis
• To see similarities across the sensory modalities
• To become more attuned to multi-sensory interactions

Grading Information^5

• 25% each for 2 midterms
• 32% comprehensive final
• 3% each for 6 lab reports - due at the end of the lab
• Bonus for participating in a psych or cogsci experiment AND writing a paragraph description of the study

You are responsible for knowing the lecture material and the assigned readings. Read the readings before class and ask questions in class.

Last Lecture^7

Beyond V1 (extrastriate processing)

Midterms look quite good for the most part

This Class^8

Color vision

Magno/parvo review^10

Magno pathway transmits information about motion and low spatial frequency

Parvo pathway transmits information about Red-green distinctions in high spatial frequency

Koniocelullar pathway more recently discovered transmits information about blue-yellow

The magno cells form the major input to the dorsal stream (parietal pathway)(where or how pathway). The parvo cells form the major input to the ventral stream (temporal pathway)(what pathway)

But there is significant crosstalk (especially to ventral stream)

• Color is related to wavelength of light

Color Circle^13

http://colorvisiontesting.com

Color circle shows perceptually similarity of colors (neigboring colors are perceptually similar)

Color Circle^14

http://www.sapdesignguild.org/resources/glossary color/index1.html

Color circle shows perceptually similarity of colors (neigboring colors are perceptually similar)

Adding more white desaturates a color (the color has less saturation when more white is added)

Aside: Additive color mixing vs Subtractive color mixing^16

When you add lights you add the spectrum

Paints have color because they absorb proportions of some wavelengths (more than others) and reflect the rest

When you add paints you combine the absorption spectra. This decreases the reflected light and is called subtractive color mixing.

(draw diagram on the board)

Trichromatic theory^17

Based on color matching experiment: Have subjects match a light of one wavelength by varying the strengths of three lights of three other wavelengths

People with normal color vision can do the match with any 3 wavelengths (as long as you can’t make any one from the other two). We will see that people with impaired color vision can match with less than 3 wavelengths.

Theory goes that there are 3 different types of detectors with different spectral sensitivies. The pattern of activity across the three types codes for the color.

The different cones have slightly different opsins which cause them to be^19 differentially selective absorption spectra

We can’t distinguish all types of color stimuli^20

e.g. We can match any one wavelength with a mix of three others

color metamers – two different wavelength mixes that can’t be distinguished