perception exam 2 Flashcards
functions of color
-help us classify and identify objects
-facilitates the perceptual organization of elements into objects
-evolutionary advantage for foraging food
-enhances contrast (helps recognize scenes)
-help us perceive emotions (yellow = happy)
origins of color
- ## evolutionary: began as a way to identify good fruit
Newton’s ideas on color
1960’s: thoughts white light was made up of all different colored light
-discovered that different colored light has different physical properties & bends at different angles
-also, individual colors do not split up so not made of other colors
-different physical properties = our perception of color
light as wavelengths
-our perception of color depends on the wavelength of light that reaches our eyes
-visible light is differently colored waves
450-490 nm = blue
500-575 = green
575-590 = yellow
590=620 = orange
620-700 = red
reflectance and transmission
-the colors of objects are largely determined by the wavelength of light that are reflected from the objects
reflectance curves
charts that have 2 axes (wavelength on x, reflectance % on y)
-chart how color’s reflectance changes as the wavelength of light changes
selective reflection
when an object reflects some wavelengths of the spectrum more than others
achromatic and chromatic colors
chromatic = colors with hue, such as yellow, blue, red or green (occurs when some wavelengths are reflected more than others)
achromatic = light is reflected equally across the spectrum (grey, white and black)
additive color mixing
-ex: light
mixing light causes more wavelengths to be reflected (each light adds wavelengths to the mixture)
mixing multiple colors in additive = white light because all are reflected
subtractive color mixing
-ex: paint, playdough, water
both objects still absorb the same wavelengths
the only wavelengths reflects are those reflected by both objects
-most paints reflect a band of wavelengths. it paints didn’t reflect a range of wavelengths, then many of the color-mixing effects of paints that we take for granted would not occur
hue - perceptual dimension of color
-chromatic colors
-what color we see
ex: red, green, yellow, blue
saturation - perceptual dimension of color
-intensity of a color
-more white = less saturation
-desaturation = washed out
value - perceptual dimension of color
-lightness of a color
-darker color = less value
Munsell Color System
a chart that includes the 5 primary hues (red, yellow, green, blue, and purple), and charts the hue, saturation, and value
-hue is around the wheel in a circle
-saturation is from the core/inside of the wheel out
-value is bottom to top
trichromacy of color vision - cone spectral sensitivity
Young-Hemholtz theory: color vision is based on 3 principle colors, and combinations of these colors; we have 3 different receptor mechanisms (3 types of cones but only 1 type of rod)
Each type of cone/receptor mechanism have different spectral sensitivities
respond to short, medium, or long wavelengths
opponent process theory of color vision
-the aspects of our color perception are difficult to explain by the trichromatic theory alone
-a theory proposed by Herring that states we have two types of color opponent cells: red-green opponent cells & blue-yellow opponent cells
-responses oppose each other, one inhibitory and one excitatory
-opponent neurons: excitatory responses to wavelengths in one part of the spectrum and an inhibitory response to wavelengths in the other part of the spectrum
-some neurons are turned on by red but off by green
-related to afterimage effect: to account for phenomena, like complementary afterimages, Herring proposed that we have 2 types of color opponent cells
-afterimages cannot be explained by trichromatic theory alone, which is why our current understanding of color vision is a combination of the 2 theories
color blindness
-8% of men, less than 1% of women
monochromats: have no functioning cones and respond to light like black and white film
dichromats: have 2 functioning cone systems (red or green cones do not function)
color constancy
-perception of colors as relatively constant despite changing light sources
-works best when an object is surrounded by many colors
-chromatic adaptation: occurs when prolonged exposure to chromatic color leads to receptors having decreased sensitivity & we do not perceive a change in different light
-adaptation occurs to light sources leading to color constancy
-sunlight has approx. equal amounts of energy at all visible wavelengths
-tungsten lighting has more energy in the long-wavelengths
-LED light
-objects reflect different wavelengths from different sources of light
-Partial color constancy: view color to slightly change, even though wavelengths and stimuli are changing quite a bit
-Full color constancy: our perception does not change even though stimuli does
memory color
our knowledge about the typical colors of the environment
-impacts perception of color
ex: we know that a stop sign is red, so we see it as more red
lightness constancy
achromatic colors are perceived as remaining relatively constant
-perception of lightness: is not related to the amount of light reflected by an object, but is related to the percentage of light reflected by an object
The Ratio Principle: two areas that reflect different amounts of light look the same if the ratios of their intensities are the same (works when objects are evenly illuminated)
inverse projection problem
idea that a particular image on the retina could have been caused by an infinite number of different objects
-objects/stimulis can be ambiguous
Gibson perception for action theory
scientist who was tired of studying perception in the lab, he wanted to study perception in natural contexts & in action
became popular in 1980’s
-perception for action theory: perception evolved for our ability to act on and within our environment
-studying perception: studying the ways people interact with their environment
ecological approach to perception
-focuses on specifying the information in the environment that is used for perception
-emphasizing the study of moving observers
-determine how their movement results in perceptual information; creates perception and guides further movement
observer movement
optic flow = moving forward - expanding optic flow, moving backward - contracting optic flow
gradient flow = closer objects move faster, farther objects move slower, we use information based on this gradient to determine speed
optic flow (how is can create movement)
moving forward = expanding optic flow
moving backward = contracting optic flow
optic flow creates movement and provides information - using info. created by movement to guide further movement
-think of circle: car moving/movement - creates flow - object moving relative to car/flow - provides info. for guiding further movement - back to movement
-experiment by Lee and Aronson: children placed in swinging room where walls and ceiling swung backward and forward but floor was stationary. children swayed back and forth in response to the flow patterns created in the room
-vision has powerful effect on balance, and often overrides other sense that provide positive feedback about body placement and posture
gradient of flow
closer objects move faster
farther objects move slower
we use information based on this gradient to determine speed
focus of expansion
point in the distance where there is no flow
remains centered on destination/point of focus
hidden affordances
when there are possibilities for action, but these are not perceived by the actor
affordances
the information that indicates how an object can be used (offers, provides for, furnishes)
not only information of what an object is but how it can be used
perceptible affordances
when there is information available such that the actor perceives and can then act upon the existing affordance
action affordances
a response to an object that involves both its affordances (what it is for) and the action associated with it
-potential for action is part of our perception of an object
functional fixedness
the tendency to use an object in the way that it is traditionally used
-ex: use the screwdriver as a weight, and tie it to the end of one rope. swing it towards the other rope to tie the knot