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AP Psychology Chapter 5 Review – Sensation
Sensation – detect physical energy (a stimulus) from the environment and convert it into neural signals; the process by
which our sensory receptors and nervous system receive and represent stimulus energies from our environment
Perception – the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects
and events
 Bottom-up processing – analysis of the stimulus begins with the sense receptors and works up to the level of the brain
and mind
 Top-Down processing – information processing guided by higher-level mental processes as we construct perceptions,
drawing on our experience and expectations
Prosopagnosia – a condition in which one has complete sensation but incomplete perception
Psychophysics – a study of the relationship between physical characteristics of stimuli and our psychological experience
with them
Absolute threshold – the minimum stimulation necessary to detect a particular stimulus (light, sound, pressure, taste, or
odor) 50% of the time
Difference threshold – minimum difference between two stimuli required for detection 50% of the time, also called just
noticeable difference (JND)
- The difference threshold is not a constant amount but some constant proportion of the stimulus
Weber’s Law – two stimuli must differ by a constant minimum percentage (rather than a constant amount), to be perceived
as different
Subliminal threshold – when stimuli are below one’s absolute threshold for conscious awareness
Signal detection theory – a theory predicting how and when we detect the presence of a faint stimulus (“signal”) amid
background stimulation (“noise”). Assumes there is no single absolute threshold and that detection depends partly on a
person’s experience, expectations, motivation, and level of fatigue.
Priming – the activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory, or
response
Sensory adaptation – diminished sensitivity as a consequence of constant stimulation
Vision
Transduction – conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as
sights, sounds, and smells, into neural impulses our brains can interpret
Photo-transduction – conversion of light energy into neural impulses that the brain can understand
Light Characteristics
 Wavelength (hue/color) – the distance from one wave peak to the next
 Hue – the color we experience; the dimension of color
 Intensity (brightness) – the amount of energy in light waves; determined by a wave’s amplitude; influences brightness
 Saturation
The Eye
Cornea – transparent tissue where light enters the eye
Iris – muscle that expands and contracts to change the size of the opening (pupil) for light
Pupil – the adjustable opening in the center of the eye through which light enters
Lens – transparent structure behind the pupil that changes shape to focus images on the retina
 Accommodation – the process by which the eye’s lens changes shape to help focus near or far objects on the retina’
 Acuity – sharpness of vision
Retina – the light-sensitive inner surface of the eye, containing receptor rods and cones in addition to layers of other
neurons (bipolar, ganglion cells) that process visual information
 Bipolar cells receive messages from photoreceptors and transmit them to ganglion cells, which are for the optic nerve
 Retinal ganglion cells and thalamic neurons break down visual stimuli into small components and have receptive fields
with center-surround organization
 Rods – retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones
don’t respond
 Cones – retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in
well-lit conditions. The cones detect fine detail and give rise to color sensations
Optic nerve – carries neural impulses from the eye to the brain
 Optic nerves connect to the thalamus in the middle of the brain, and the thalamus connects to the visual cortex
Blind spot – point where the optic nerve leaves the eye because there are no receptor cells located there
Fovea – central point in the retina around which the eye’s cones cluster
Parallel processing – processing of several aspects of the stimulus simultaneously; the brain divides a visual scene into
subdivisions such as color, depth, form and movement etc.
Color constancy – color of an object remains the same under different illuminations. However, when context changes the
color of an object may look different.
Trichromatic (three-color) theory – based on behavioral experiments, Helmholtz suggested that the retina should contain
three receptors that are sensitive to red, blue and green colors
 Color blindness – genetic disorder in which people are blind to green or red colors. This supports the Trichromatic
theory.
Opponent process theory – Hering proposed that we process four primary colors combined in pairs of red-green,
blue-yellow, and black-white.
Audition
Acoustical transduction – conversion of sound waves into neural impulses in the hair cells of the inner ear
Sound Characteristics
 Frequency (pitch) – a tone’s experienced highness or lowness
 Intensity (loudness) – the strength, or amplitude of sound waves
 Quality (timbre)
Overtones – makes the distinction among musical instruments possible
The Ear
Outer ear – Pinna; collects sounds
Middle ear – chamber between eardrum and cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate
the vibrations of the eardrum on the cochlea’s oval window
Inner ear – innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs
 Cochlea – coiled, bony, fluid-filled tube in the inner ear that transforms sound vibrations to auditory signals
 Place theory – suggests that sound frequencies stimulate the basilar membrane at specific places resulting in
perceived pitch
 Frequency theory – states that the rate of nerve impulses traveling up the auditory nerve matches the frequency of
a tone, thus enabling us to sense its pitch
Conduction hearing loss – hearing loss caused by damage to the mechanical system that conducts sound waves to the
cochlea; damages in places such as eardrum
Sensori-neural hearing loss – hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve, also
called nerve deafness; also called nerve deafness
Touch
- The sense of touch is a mix of four distinct skin senses: pressure, warmth, cold, and pain.
- Only pressure has identifiable receptors. All other skin sensations are variations of pressure, warmth, cold and pain.
- Pain tells the body that something has gone wrong. Usually pain results from damage to the skin and other tissues.
Phantom limb sensations – indicate that with pain, as with sights and sounds, the brain can misinterpret the spontaneous
central nervous system activity that occurs in the absence of normal sensory input
Gate-control theory – the theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them
to pass on to the brain. The “gate” is opened by the activity of pain signals traveling up small nerve fibers and is
closed by activity in larger fibers or by information coming from the brain.
Taste – our sense of taste involves several basic sensations: sweet, sour, salty, bitter, and umami (meaty taste)
Sensory interaction – the principle that one sense may influence another, as when the smell of food influences its taste
Smell - like taste, smell is a chemical sense; unlike taste, there are many different forms of smell.
Body Position and Movement
Kinesthesis – the sense of our body parts’ position and movement
Vestibular sense – the sense of body movement and position, including the sense of balance