Answer: white or gray
1. opponency: blue and yeallow are opponent colors, so when both are present in equal amounts, neither is perceived.
2. ratio of cone excitations: when blue and yellow light are both present, the three cone classes are stimulated in about equal amounts which results in perception of white.

2. (2 points) What color do you get when you mix blue and yellow paint? Why?

Answer: Blue and yellow paint make green. This is because green is the only wavelength that is not absorbed fully by either of the pigments.

3. [TRUE or FALSE] In a color-matching experiment, if we double the intensity of the test light, cone absorptions will double, and so will the knob-settings of an observer trying to match that light.

Answer: TRUE

4. Which can be used to accomplish color constancy?

a. the yellow detector cells that get inputs from both L and M cones

b. the widely spread cones in the periphery

c. the double-opponent cells in layer 4 of V1

d. three primary colors (as long as their brightness can be adjusted)

e. cheer with color guard

Answer: C

5. (2 points) Which of the following will serve to increase d'?
(please circle all that apply)

a. increasing signal intensity

b. decreasing signal intensity

c. adopting a higher criterion

d. adopting a lower criterion

e. increasing the noise

f. decreasing the noise

Answer: A and F

6. What is the basic point of Weber's Law? (10 words)

Answer: difference threshold depends on the baseline intensity