Sensation and Perception

Sensation

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 that begins with the sensory receptors and works up to the brain’s integration of sensory information

Top-down processing

information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations.

Selective attention

the focusing of conscious awareness on a particular stimulus.

Cocktail party effect

your ability to attend to only one voice among many (while also being able to detect your own name in an unattended voice)

inattentional blindness

failing to see visible objects when our attention is directed elsewhere

change blindness

failing to notices changes in the enviroment

choice blindness

people fail to notice that their choices or preferences have been subtly manipulated

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 brain can interpret.

psychophysics

the study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them.

absolute threshold

the minimum stimulation needed to detect a particular stimulus 50 percent of the time.

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 alertness.

subliminal

below one’s absolute threshold for conscious awareness.

Difference threshold

the minimum difference between two stimuli required for detection 50 percent of the time. increases with SIZE of stimulus

Weber’s law

the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount)

Sensory adaptation

diminished sensitivity as a consequence of constant stimulation.

Perceptual set

a mental predisposition to perceive one thing and not another.

what may affect perception

• context effects (where they come from, their culture, size difference)

• emotion and motivation

Extrasensory perception (ESP)

the controversial claim that perception can occur apart from sensory input; includes telepathy, clairvoyance, and precognition.

Parapsychology

the study of paranormal phenomena, including ESP and psychokinesis

Hue

determined by wavelength

the dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forth

intensity of color

determined by amplitude

determines brightness

amount of energy in waves

wavelength

short = high freq, long = low freq

red colors, low pitched sounds

amplitude

great amp = bright color/sounds, small amp = dull colors/quiet sounds

pupil

the adjustable opening in the center of the eye through which light enters

iris

a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening

lens

the transparent structure behind the pupil that changes shape to help focus images on the retina.

retina

the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information.

accommodation

the process by which the eye’s lens changes shape to focus near or far objects on the retina.

Rods

retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don’t respond

share bipolar cells

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

the nerve that carries neural impulses from the eye to the brain.

Fovea

the central focal point in the retina, around which the eye’s cones cluster.

Feature detectors

nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement.

Process of viewing things

scene → retinal processing (rods, cones, bipolar cells ganglion cells) → feature detection → parallel procesing → recognition

Young-helmholtz trichromatic (three-color) theory

the theory that the retina contains three different color receptors—one most sensitive to red, one to green, one to blue—which, when stimulated in combination, can produce the perception of any color

opponent-process theory

the theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green.

Gestalt

an organized whole. Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes

Figure-ground

the organization of the visual field into objects (the figures) that stand out from their surroundings (the ground).

Grouping

the perceptual tendency to organize stimuli into coherent groups. Includes proximity, continuity, and closure

Depth perception

the ability to see objects in three dimensions although the images that strike the retina are two-dimensional; allows us to judge distance.

Binocular cues

depth cues, such as retinal disparity, that depend on the use of two eyes

Retinal disparity

a binocular cue for perceiving depth: By comparing images from the retinas in the two eyes, the brain computes distance—the greater the disparity (difference) between the two images, the closer the object

Monocular cues

depth cues, such as interposition and linear perspective, available to either eye alone.

What are the monocular cues?

Relative height, relative size, interposition, relative motion, linear perspective, light and shadow

stroboscopic movement

brain also perceives continuous movement in a rapid series of slightly varying images

phi phenomenon

an illusion of movement created when two or more adjacent lights blink on and off in quick succession

Perceptual constancy

perceiving objects as unchanging (having consistent shapes, size, brightness, and color) even as illumination and retinal images change.

Color constancy

perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object.

perceptual adaptation

in vision, the ability to adjust to an artificially displaced or even inverted visual field

Brightness(lightness) constancy

our ability to perceive an object as having a constant lightness even when its illumination—the light cast upon it—changes.

Shape constancy

our ability to perceive familiar objects (such as an opening door) as unchanging in shape.

Size constancy

perceiving objects as unchanging in size despite their changing retinal images

Audition

the sense or act of hearing. highly adaptive. attuned to variation in sounds (difference in human voice)

Amplitude determines (sound)

loudness

Frequency determines (sound)

pitch (short wave = high pitch)

middle ear

the chamber between the eardrum and cochlea containing three tiny bones (hammer, anvil, and stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window.

cochlea

a coiled, bony, fluid-filled tube in the inner ear; sound waves traveling through the cochlear fluid trigger nerve impulses.

Inner ear

the innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs

Sensorineural hearing loss

hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerves. (Also called nerve deafness.)

can be caused by disease. mainly caused by heredity, aging, and prolonged exposure to loud noise.

Conduction hearing loss

hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea.

Cochlear implant

a device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea.

How does the brain interpret loudness?

The number of activated hair cells

Place theory (pitch)

in hearing, the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated.

Frequency theory

in hearing, the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch

Volley principle

Alternating neural firing allows for frequency theory to take place.

Why do we have two ears?

The ear closer to the sound receives a more intense sound. Allows us to detect location.

Four basic variations of touch

pressure, warmth, cold, and pain

Nociceptors

sensory receptors that detect hurtful temperatures, pressure, or chemicals

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.

brain-to-spinal-cord messages can also close the gate

the taste sensations

sweet, sour, salty, bitter, umami, fat

how often do taste receptors reproduce themselves

one to two weeks

Anosmia

people who are unable to smell

Kinesthesia

the system for sensing the position and movement of individual body parts.

Vestibular sense

the sense of body movement and position, including the sense of balance.

Vestibular sacs

Connect the canals with the cochlea, contain fluid that moves when your head rotates or tilts

Sensory interaction

the principle that one sense may influence another, as when the smell of food influences its taste

McGurk effect

the brain integrates conflicting auditory and visual information, leading to the perception of a sound that is different from what is actually heard or seen, a "fused" sound

Embodied cognition

in psychological science, the influence of bodily sensations, gestures, and other states on cognitive preferences and judgments.
ex. (cold people = cold room)

synesthesia

one sort of sensation (such as hearing sound) produces another (such as seeing color)

glial cells

provide support and nourishment to neurons, including those involved in the visual systems

ganglion cells

pass visual info from bipolar cells to the brain via optic nerve.