Flashcards in Sensation and Perception Deck (48):
What is an absolute threshold?
The minimum stimulus energy needed to activate a sensory system
What is subliminal perception?
Perception of stimuli below a threshold; in this case, of conscious awareness (perception that occurs without conscious awareness)
What is a difference threshold
How different (in magnitude) two stimuli must be before they are perceived to be different
What is just noticeable difference?
Same as difference threshold (how different two stimuli must be before they are perceived to be different) but in different units (jnd)
What is Weber's Law?
What's important in producing a jnd is not the absolute difference between the two stimuli, but the ratio of them; change needed = standard stimulus
What is Fechner's Law?
Expresses the relationship between the intensity of the sensation and the intensity of the stimulus; derived from Weber's law; sensation increases more slowly as intensity increases (might be incorrect - replaced with Stevens' Power Law)
What is signal detection theory?
When measure thresholds in experiments, measuring what the person says she received rather than what she actually sense; other, non-sensory, factors influence what the subject says she senses; leads to response bias
What are ROC curves?
Used to graphically summarize a subject's response in signal detection experiment; refined by John A. Swets; includes: (1) Hit - signal and perception; (2) Miss - signal and no perception; (3) False alarm - no signal and perception; (4) Correct negatives - no signal and no perception
What are the three steps that make up the processing of sensory information?
2. Transduction - translation of physical energy into neural impulses or action potentials
3. Electrochemical energy is sent to the various projection areas along neural pathways; project areas further analyze sensory input
What is the cornea?
Clear, domelike window in front of you eye; gathers and focuses incoming light
What is the pupil?
Hole in the iris; contracts in bright light and expands in dim light to let more light in
What is the iris?
Colored part of the eye; has involuntary muscles and autonomic nerve fibers; controls the size of the pupil and therefore the amount of light in the eye
What is the lens?
Lies right behind the iris; helps to control the curvature of the light coming in and can focus near or distant objects on the retina
What is the retina?
In the back of the eye; screen filled with neutral elements and blood vessels; image-detecting part of the eye
What is the duplexity or duplicity theory of vision?
Retina contains two kinds of photoreceptors; light passes through the intermediate sensory neurons before reaching and stimulating the photo-receptors; blind spot where the optic nerve leaves the eye
What do cones do?
Cones are used for Color vision and for perceiving fine detail; most effective in bright light
What do rods do?
In reduced illumination, rods function best and allow perception of achromatic colors; low sensitivity to detail; not involved in color vision
What is the fovea?
The middle section of the retina; only cones; best visual acuity; most sensitive in normal daylight vision
What is the optic chasm?
Fibers from nasal half of retina cross paths; from the optic chasm, the info goes to several places: (1) lateral geniculate nucleus of the thalamus; (2) visual cortex in the occipital lobe; (3) super colliculus
What was Hubel and Wiesel's contribution to psychology?
Found a neural basis for feature detection theory; suggests that certain cells are maximally sensitive to certain features of stimuli; used single-cell recording to detect microelectrode small can't be seen with an ordinary microscope in the cortex
What is illumination?
Physical, objective measurement of amount of light falling on a surface
What is brightness?
Subjective impression of intensity of a light stimulus
What is adaptation?
Our ability to adapt to darker spaces or lighter spaces
What is simultaneous brightness contrast?
When something appears brighter when surrounded by something dark than when surrounded by something light
What is lateral inhibition?
Adjacent retinal cells inhibit one another; sharpens and highlights borders between light and dark areas
What is the Young-Helmhotz theory or Trichromatic theory of vision?
Retina contains three types of cones that are sensitive to different colors; colors produced by combined stimulation of these receptors - blue/green/red primary
What is the Opponent-Process theory of color vision?
Suggested that four primaries: blue, green, yellow, red, were arranged in opposing pairs; red - excite red/green cell; green inhibit (can't have reddish green); also included black-white as an opposing pair
J. J. Gibson
studied texture gradients: variations in perceived surface texture as a function of the distance from the observer. As the distance increases, so does the perceived density
next time in car or train – look at horizon – fix gaze on object half-way between you and horizon; objects closer than fixed point appear to move in the same direction as you do
Kinetic depth perception
when object moves but perceiver stays in the same place
distance between the eyes provides us with two slightly disparate views on the world
Called binocular parallax; When combine these two, get a perception of depth; Only one that requires two eyes: binocular depth cue; all others: monocular depth cue
cue for depth perception when object A covers or overlaps with object B
• We see object A as being in front
as objects get farther away, their images on the retina get smaller
Can tell how far away something is from you relative to another by comparing the size of the images on the retina with what you know about their actual sizes
convergence of parallel lines in the distance
Studied by George Berkeley
Five laws explain form perception:
o Proximity: close together = unit
o Similarity: similar = grouped together
o Good continuation
o Pragnanz: perceptual organization will always be as regular, simple, and symmetrical as possible
• Subjective contours: perceiving contours/shapes that aren’t really there
The amplitude or physical intensity of a sound wave largely determines loudness
Frequency, the pace of vibrations or sounds waves per second for a particular sound, determines pitch. Low frequency is perceived as low pitch and vice versa. Frequency is measured in hertz (Hz), and humans best hear frequencies around 1000 Hz
Timbre comes from the complexity of the sound wave
Outer ear consists of the parts that you see called pinna and the auditory canal. Vibrations from sound move down this canal to the middle of the ear
Middle ear begins with tympanic membrane (also known as the eardrum), which is stretched across the auditory canal. Behind this membrane are the ossicles (three small bones), the last of which is the stapes. Sound vibrations bump against the tympanic membrane, causing the ossicles to vibrate.
The inner ear is responsible for both hearing and balance. It begins with the oval window, which is tapped upon by the stapes. These vibrations then activate the fluid-filled, snail-shell-like cochlea, which contain the ear parts for hearing (the basilar membrane and the organ of corti). The movement of the cochlear fluid activates the hair-cell receptors on the basilar membrane and the organ of corti. This movement on the basilar membrane is called the traveling wave. The vesibular sacs (which also respond to hair movement) are sensitive to tilt and provide our sense of balance.
How does ear interpret sound?
Receptor cells in the inner ear activate nerve cells that change the information into an electrical message the brain can process. The auditory system that leads to the auditory cortex consists of olivary nucleus, the inferior colliculus, and the medial geniculate body.
perception and cognition are largely innate
asserts that the perception is the sum total of sensory input. The world in understood through bottom-up processing.
asserts that people tend to see the world as comprised of organized wholes.
perceptual development is the increasing ability of a child to make finer discriminations among stimuli. The optic array, or all of the things a person sees, trains people to perceive.
takes place when receptors for a particular sense detect a stimulus. The receptive field is the part of the world that triggers a particular neuron.