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object agnosia
Inability to recognize objects using only vision.
top-down processing
a process whereby our existing knowledge of objects influences how we perceive them
bottom-up processing
a process whereby physical stimuli influence how we perceive them
recognition
the ability to match a presented item with an item in memory
representation
the storage and/or reconstruction of information in memory when that information is not in use
perceptual organization
the process by which multiple objects in the environment are grouped, allowing us to identify multiple objects in complex scenes
grouping
the process by which elements in a figure are brought together into a common unit or object
Segregation
the process of distinguishing two objects as being distinct or discrete
figure-ground organization
the experience viewers have as to which part of an image is in front and which part of an image is in the background of a particular scene
Gestalt Psychology
In terms of vision, gestalt argues that what we see is greater than its individual parts. That is, the process of perception are designed to see the scene rather that bits of light here and there. Stimuli were sufficiently rich in structure to allow the perceptual system to extract meaning directly from the stimuli rather than building it up from an image of thought. The whole is different from the sum of its parts.
How symmetry and convexity affect figure-ground organization
Symmetry:
images that are more likely to be seen as figure and therefore in the foreground, whereas less symmetrical images are more likely to be perceived as background
Convexity:
Images with convex borders are more likely to be seen as figure, whereas those with concave borders are more likely to be seen as ground. (stevens and brookes 1988)
law of good continuation
grouping law stating that edges that are smooth are more likely to be seen as continuous than edges that have abrupt or sharp angles
law of proximity
grouping law stating that elements that are close together tend to be perceived as a unified group
law of similarity
grouping law stating that elements that are similar to one another tend to be perceived as a unified group
Law of Symmetry
grouping law stating that elements that are symmetrical to each other tend be be perceived as a unified group
perceptual interpolation
the process by which the visual system fills in hidden edges and surfaces in order to represent the entirety of a partially visible object
edge completion
the perception of a physically absent but inferred edge, allowing us to complete the perception of a partially hidden object
illusory contours
perceptual edges that exist because of edge completion but are not actually physically present
recognition by components
a theory stating that object recognition occurs by representing each object as a combination of basic units (geons) that make up that object; we recognize an object by the relation of its geons
Geons
the basic units of objects, consisting of simple shapes such as cylinders and pyramids
viewpoint invariance
the perception that an object does not change when an observer sees the object from a new vantage point
template theories
theories of pattern recognition which assert that there is a mental representation for each of the patterns to be recognized
Area V4
an area of the brain involved in both color vision and shape perception
inferotemporal area
the area of the temporal lobe involved in object perception; it receives input from V4 and other areas in the occipital lobe
fusiform face area
an area in the inferotemporal area of the temporal lobe that specializes in recognizing familiar faces; located in the ventral surface of the temporal lobe
occipital face area
an area of the brain in the occipital lobe, associated with recognizing faces as distinct from other objects; located in the extrastriate cortex and is strongly connected to the FFA
Prosopagnosia
inability to recognize faces but other forms of visual object recognition are relatively intact. For example, a person with prosopagnosia will have difficulty recognizing particular people but will not have difficulty identifying roses or gloves.
Grill-Spector experiment
examined the role of the FFA in face recognition using functional magnetic resonance imaging (fMRI) technology. participants briefly saw Harrison Ford's face followed by a mask, or a control stimulus followed by a mask (a). In (b), we can see the activity in the FFA when the participant recognized the photo as Harrison Ford and when the participant did not. Note that the highest response in the FFA is for correct recognition.
parahippocampal place area (PPA)
an area within the inferotemporal cortex that appears to have the specific function of scene recognition; tuned for recognition of spatial landscapes, both indoor and outdoor scenes
topographic agnosia
a deficit in recognizing spatial landscapes, related to damage to the parahippocampal place area
Extrastraite Body Area (EBA)
an area within the inferotemporal cortex that is activated when its cells view bodies or body parts but not faces
grandmother cell theory
Theory that there is a particular cell in the ventral processing stream whose job is to fire when you see a particular object or person (such as your grandmother).
results of the Quiroga et al. Study (2005)
these data are from single cells within the human temporal cortex. One cell responded to the image of Kobe Bryant but not to the images of other people. Similarly, one cell responded to the image of the Golden Gate Bridge but not to images of other landmarks
face inversion effect
The inability to detect facial features that are inverted on an inverted face (i.e., the features would be upside down, and very obvious, if the face were turned right-side up), because we are so used to processing faces in the upright orientation.
Capgrass syndrome
The delusional belief that an acquaintance has been replaced by an identical-looking imposter. It is more commonly seen in schizophrenia, dementia, and brain trauma.
results of looser and Wheatley's study of animacy
data show participants' perceptions of whether the figures were animate or not (alive or not, realistic or not, has a mind or doesn't, can feel pain or can't); results showed we have a high criterion for recognizing animacy in a human face.
Accidental viewpoints & features
A viewing position that produces some regularity in the visual image that is not present in the world
Perceptual committees assume viewpoints are not accidental
wavelength of light and color
humans see wavelengths of light that vary between 400 and 700 nm
visual spectrum
the range of wavelengths that our eyes can detect (400-700)
heterochromatic light
white light, consisting of many wavelengths
monochromatic light
light consisting of one wavelength
spectral reflectance
the ratio of light reflected by an object at each wavelength
achromatic lightness
when objects reflect all light wavelengths equally; white (90%) to gray (50%) to Black (10%)
hue
the color quality of light, corresponding to the color names we use, such as orange, green, indigo, and cyan; hue is the quality of color
quality
the value that changes but does not make the value larger or smaller
saturation
the purity of light; the more saturated the stimulus is, the stronger the color experience; the less saturated the stimulus, the more it appears white or gray or black (achromatic)
lightness
the psychological experience of the amount of light that gets reflected by a surface
Brightness
the perceived intensity of the light present
additive color mixing
the creation of a new color by a process that adds one set of wavelengths to another set of wavelengths
subtractive color mixing
color mixing in which a new color is made by the removal of wavelengths from a light with a broad spectrum of wavelengths
metamer
a psychophysical color match between two patches of light that have different sets of wavelengths
color matching experiments
observers adjusted the amounts of three different wavelengths of light mixed together in a "comparison field" until the color of this mixture matched the color of a single wavelength in a "test field"
s-cone
the cone with its peak sensitivity to short-wavelength light, around 420 nm (blue)
M cone
the cone with its peak sensitivity to medium-wavelength light, around 535 nm (green)
L-cone
the cone with its peak sensitivity to long-wavelength light, around 565 nm (yellow)
the response of cones to a 500-nm light
each cone system responds to this light but with a weaker or stronger response. Color is partially determined by this pattern of responses of each cone to any particular wavelength
Univariance
the principle whereby any single cone system is colorblind, in the sense that different combinations of wavelength and intensity can result in the same response from the cone system
why more than one receptor is necessary to see in color?
we are unable to see color with only one cone, with the help of three cones that all respond in different levels of strength, we are able to perceive color and its intensities.
trichromatic theory of color vision
the theory that the color of any light is determined by the output of the three cone systems in our retinae
the three cones systems of the retinae
S,M, and L cones
the opponent theory of color perception
the theory that color perception arises from three opponent mechanisms, for red-green, blue-yellow, and black-white
Hering's opponent-process theory
all colors on the color circle can be represented by two pairs of opposing colors
sorting into four groups
green, red, yellow, and blue (western and non-western cultures support this)
perception of color combinations
non-primary colors look like combinations of two primary colors but our perception of color supports that red and green don't combine and blue and yellow don't combine (it it hard to imagine with color they would make)
afterimages
visual images that are seen after an actual visual stimulus has been removed
simultaneous color contrast
a phenomenon that occurs when our perception of one color is affected by a color that surrounds it
findings that support opponent theory
color combination perception, four basic color group sorting, afterimages, and simultaneous color contrast
Cone-opponent cells in LGN
neurons that are excited by the input from one cone type in the center but inhibited by the input from another cone type in the surround
color-opponent cells in V1
neurons that are excited by one color in the center and inhibited by another color in the surround , or neurons that are inhibited by one color in the center and excited by another color in the surround
double-opponent cell
cells that have a center, which is excited by one color and inhibited by the other, in the surround, the pattern is reversed
color deficiency
the condition of individuals who are missing one or more of their cone systems
Rod monochromacy
a condition in which a person has no functioning cones and therefore can be described as truly color blind
cone monochromacy
(extreme rare) they have one cone but not the other two; s-cone monochromacy is more common in men, has similar side effects to rod monochromacy but less severe, also have poor acuity and high sensitivity to bright light
Types of Color Vision
tritanopia, protanopia, and deuteranopia
Tritanopia
a lack of s-cones, leading to blue-yellow color deficiency; this trait is rare and is not sex-linked
Protanopia
a lack of L-cones, leading to red-green deficiency; this trait is sex linked and thus more common in men
Deuteranopia
a lack of M-cones, leading to red-green deficiency; this trait is sex linked and thus more common in men
cortical achromatopsia
loss of color vision due to damage to the occipital lobe
light source
monochromatic light source, yellow light; Under these conditions, only the yellow-blue opponent channel can help us do color discriminations. You will experience the world as a color deficient individual does.
errors we have made
Brown-blue: look alike
Red-green: difficult to tell them apart
Yellow-orange: look alike
yellow surfaces
this color is reflected and coded along the yellow-blue channel
red and green surfaces
these surfaces reflect a little bit of yellow light, however red and green cannot be coded by the yellow channel
blue surfaces
blue is the opponent color of yellow. So, the yellow light will remove or "kill" the blue (go back to the Hue Cancellation experiments). Blue surfaces reflect only very little light, so they will look very dark.
hue cancellation
an experiment in which observers cancel out the perception of a particular color by adding light of the opponent color
hue cancellation experiments
- Start with a color, such as bluish green.
- The goal is to end up with pure blue.
- Shine some red light to cancel out the green light.
- Adjust the intensity of the red light until there is no sign of either green or red in the blue patch.
brown surfaces
these surfaces don't reflect a lot of light in general, so they will look dark.
orange surfaces
what is orange? Yellow + red. Yellow is reflected but red is not and cannot be coded by the yellow channel.
constancy
the ability to perceive an object as the same under different conditions
color constancy
the ability to perceive the color of an object despite changes in the amount and nature of illumination
lightness constancy
the ability to perceive the relative reflectance of objects despite changes in illumination
color based acuity
1) cones are clustered together around the fovea and are in the
midget system (one photoreceptor - one ganglion cell) giving us
spatial acuity.
2) Three different types of cones respond maximally to three
different wavelengths (S, M and L cones).
Does everyone see colors the same way?
No
About 8% of male population, 0.5% of female population has some form of color vision deficiency: Color blindness
cultural relativism
not judging a culture but trying to understand it on its own terms
Synesthesia
describing one kind of sensation in terms of another ("a loud color", "a sweet sound")
Watercolor illusion in synesthesia
brighter chromatic contour on the inside and dark chromatic contour on the outside. The brighter color spreads into the entire enclosed area
what parts of fovea see the motion?
motion thresholds are a function of what parts of the retinae are seeing the motion. We have rather poor motion thresholds. there are simply some stimulus that are too fast or too slow for us to make sense of
real motion
motion in the world created by continual change in the position of an object relative to some frame of reference
apparent motion
the appearance of real motion from a sequence of still images presented one after the other
correspondence problem
how the visual system know if an object seen at time 1 is the same object at time 2
induced motion
an illusion whereby one moving object may cause another object to look a if it is moving