PERCEPTION
Perception: brain’s process of organizing and interpreting sensory information to give it meaning
THRESHOLDS
A. Absolute threshold: minimum amount of energy we can detect (50% of time)
B. Difference threshold: smallest difference in stimulation required to discriminate two stimuli (50% of time)
C. Terminal threshold: upper limit after which no stimuli can be perceived
D. Weber’s Law: two stimuli must differ by a constant minimum percentage, not constant amount
STIMULUS DETECTION
A. Signal detection theory (J.A. Swet)
1. Sensitivity to stimuli depends on many factors besides physical intensity and sensory abilities
2. People can detect stimuli because they want to (false alarm)
B. Receiver operating characteristic (ROC) curves: graphical representations of person’s sensitivity to stimuli
APPROACHES & THEORIES TO PERCEPTION
A. Information-processing approach: perception is the process of representing information from the world internally
B. Ecological approach: Perception’s function is to bring organism in contact with environment and increase adaptation
A. Top-down processing:
B. Bottom-up processing:
C. Structuralist theory: perception is the sum of total sensory input (bottom-up processing)
D. Gestalt theory: people see world as organized whole (top-down processing)
1. Pragnaz: overarching gestalt idea that world is organized as meaningful, symmetrical, and simple
2. Closure: close objects
3. Proximity: group items near in space
4. Continuation: create a whole figure based on our expectations rather than what is seen
5. Symmetry: make figures out of symmetrical images
6. Constancy: perceive objects in a way that is familiar even when retinal images changes
7. Minimum principle: see what is easiest or logical
VISUAL PERCEPTION
A. Figure-ground relationship: relationship between meaningful part of a picture and the background (goblet example)
B. Depth perception: ability to perceive objects in 3-D
1.
2.
Binocular disparity: depth cues based on combination of images from both eyes
Monocular cues: depth cues that can be extracted from the image in one eye
a. Familiar of apparent size: know how far away an object is if we know how big it should be (orange is one size)
b. Interposition of overlap: overlapping objects show which objects is closer
c. Texture gradient: texture becomes denser the farther it is away
d. Linear perspective: object farther away take up less space on retina and appear to converge
3. Visual cliff: studies to determine if depth perception is innate, infants see depth by 6 months
C. Perceptual constancy (size, shape, and brightness): objects appear the same even though our view of them change
D. Illusions: occur when two objects produce the same retinal image but are perceived as different images
1. Muller-Lyon illusion: two lines with opposite-pointing arrows appear different lengths
2. Ponzo illusion: two horizontal lines appear unequal because of vertical lines that slant inward
3. Ambiguous figures: perceived as different things depending on how you look at them (duck-rabbit)
4. Figure-ground reversal: perceived as different things depending on which part is figure and which is background (vase-face)
5. Moon illusion: moon appears bigger on horizon because the aid of visual cues
6. Phi phenomenon: tendency to perceive smooth motion (cartoons)
7. Autokinetic effect: single point of light viewed in darkness will appear to move because our eyes are constantly moving