Sensation and Perception

Sensation

The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.

(Eg. Your ears picking up sound vibrations or eyes detecting light waves)

Sensory receptors

Sensory nerve endings that respond to stimuli (Ex. Hair in ears)

Perception

The process by which our brain organizes and interprets sensory information, enabling us to recognize meaningful objects and events.

(Eg. Recognizing your friend's face (or) an object)

Bottom-up processing

Analysis that begins with the sensory receptors and works up to the brain's integration of sensory information.

(Eg. Noticing the details of new object you've never seen before and figuring out what it is)

Top-down processing

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

(Eg. Reading messy handwriting but still understanding the words because you know the language)

Transduction

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

(Eg. The dimmest light you can see in the dark)

Signal detection theory

A theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise).

Assumes that there isn't an absolute threshold and it depends on the person

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. We experience the difference threshold as a just noticeable difference.

(Eg. Noticing the difference between two shades of blue)

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).

(Eg. Two lights must differ in intensity by 8 percent

Priming

The unconscious activation of certain associations in memory, which influences perception, behavior, or response.

(Eg. After seeing the word "yellow" → faster to recognize the word "banana")

Sensory adaptation

Diminished sensitivity as a consequence of constant stimulation.

(Eg. Getting used to the feel of your clothes on your skin)

Perceptual set

A mental predisposition to perceive one thing and not another.

(Eg. Feeling angry → interpreting neutral facial expressions as hostile

Wavelength

The distance from the peak of one light or sound wave to the peak of the next.

Hue

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

The amount of energy in a lightwave or sound wave, which influences what we perceive as brightness or loudness. Intensity is determined by the wave's amplitude.

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, and are sensitive to movement. Rods are necessary for peripheral and twilight vision.

Cones

Retinal receptors that are concentrated near the center of the retina and that function in daylight orin well-lit conditions.Cones detect fine detail and give rise to color sensations.

Optic nerve

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

Blind spot

The point at which the optic nerve leaves the eye, creating a "blind"spot because no receptor cells are located there.

Fovea

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

Trichromatic theory

The theory that the retina contains three different types of 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, blue-yellow, white-black) enable color vision.

(Eg. Some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green)

Feature detectors

Nerve cells in the brain's visual cortex that respond to specific features of the stimulus, such as shape, angle, or movement.

(Eg. Certain neurons fire only when seeing a horizontal line)

Parallel processing

Processing many aspects of a stimulus or problem simultaneously.

(Eg. When looking at a bird, you process its color, movement, and shape all at once, not one after another)

Gestalt

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

(Eg. Reading words rather than individual letters)

Figure-ground

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

Grouping

The perceptual tendency to organize stimuli into coherent groups.

(Eg. We fill in gaps to see complete objects)

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.

Visual cliff

A laboratory device for testing depth perception in infants and young animals.

Binocular cue

A depth cue, such as retinal disparity, that depends on the use of two eyes.

Retinal disparity

A binocular cue for perceiving depth. By comparing retinal images from the two eyes, the brain computes distance—the greater the disparity (difference)between the two images, the closer the object.

Monocular cue

A depth cue, such as interposition or linear perspective, available to either eye alone.

Phi phenomenon

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

(Eg. Creates an impression of a moving arrow)

Perceptual constancy

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

(Eg. A person walking toward you doesn't seem to shrink)

Perceptual adaptation

The ability to adjust to changed sensory input, including an artificially displaced or even inverted visual field.

(Eg. Getting used to a new pair of glasses)

Audition

The sense or act of hearing.

Frequency

The number of complete wavelengths that pass a point in a given time.

(Eg. per second).

Middle ear

The chamber between the eardrum and cochlea containing three tiny bones—hammer (malleus), anvil(incus), and stirrup(stapes)—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

The most common form of hearing loss, caused by damage to the cochlea's receptor cells or to the auditory nerve; also called nerve deafness.

Conduction hearing loss

A less common form of 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.

Place theory

In hearing, the theory that links the pitch we hear with the place where the cochlea's membrane is stimulated. AKA place coding.

(Eg. Low pitched sounds vibrate near the end of the cochlea)

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. AKA temporal coding.

Hypnosis

A social interaction in which one person (the hypnotist) suggests to another (the subject) that certain perceptions, feelings, thoughts, or behaviors will spontaneously occur.

Dissociation

A split in consciousness, which allows some thoughts and behaviors to occur simultaneously with others.

(Eg. Hypnotized people feeling pain but saying that it doesn't bother them)

Posthypnotic suggestion

A suggestion, made during a hypnosis session, to be carried out after the subject is no longer hypnotized.

(Eg. used by some clinicians to help control undesired symptoms and behaviors)

Gustation

Our sense of taste

Olfaction

Our sense of smell

Kinesthesia

Our movement sense—our system for sensing the position and movement of individual body parts.

Vestibular sense

Our balance sense—our sense of body movement and position that enables our sense of balance.

Sensory interaction

The principle that one sense can influence another. (Eg. when the smell of food influences its taste)

Embodied cognition

The influence of bodily sensations, gestures, and other states on cognitive preferences and judgments.

(Eg. Walking tall → feeling more confident)

Extrasensory perception

The controversial claim that perception can occur apart from sensory input.

(Eg. Telepathy, clairvoyance, and precognition)

Parapsychology

The study of paranormal phenomena, including ESP and psychokinesis (also called telekinesis).