Sensation and Perception

Chapter 3

Sensation

The process of detecting a physical stimulus, such as light, sound, heat, or pressure.

Perception

The process of integrating, organizing, and interpreting sensation.

Sensory Receptors

Specialized cells unique to each sense organ that respond to a particular form of sensory stimulation

Transduction

The process by which a form of physical energy is converted into a coded neural signal that can be processed by the nervous system

Absolute Threshold

The smallest possible strength of a stimulus that can be detected half the time.

Difference Threshold

The smallest possible difference between two stimuli that can be detected half the time; also called just noticeable difference.

Weber’s Law

A principle of sensation that holds the size of the just noticeable difference will vary depending on its relation to the strength of the original stimulus

Sensory Adaption

The decline in sensitivity to a constant stimulus

Subliminal perception

The perception of stimuli that are below the threshold of conscious awareness

Wavelength

The distance from on wave peak to another

Cornea

A clear membrane covering the visible part of the eye that helps gather and direct incoming light

Pupil

The opening in the iris that change size to let in different amounts of light

Iris

The colored part of the eye, which is the muscle that controls the size of the pupil

Iridology

A pseudoscience based on the unproven notion that the physical and psychological functioning of an individual is represented in marking of the iris

Lens

A transparent structure located behind the pupil that actively focuses, or bends, light as it enters the eye

Accommodation

The process by which the lens changes shape to focus incoming light so that it falls on the retina

Retina

A thin, light-sensitive membrane located at the back of the eye that contains the sensory receptors for vision.

Rods

The long, thin light-sensitive membrane located at the back of the eye that contains the sensory receptors for vision and night vision

Cones

The short, thick, pointed sensory receptors of the eye that detect color and are responsible for color vision and visual acuity

Fovea

A small area in the center of the retina, composed entirely of cones, where visual information is most sharply focused.

Optic Disk

Area of the retina without rods or cones where the optic nerve exits the back of the eye

Blind spot

The point at which the optic nerve leaves the eye; producing a small gap in the field of vision

Ganglion cells

In the retina, the specialized neurons that connect to the bipolar cells, the bundled axons of the ganglion cells form the optic nerve

Bipolar cells

In the retina, the specialized neuron that connects the rods and cones with the ganglion cells.

Optic nerve

The thick nerve that exits from the back of the eye and carries visual information to the visual information to the visual cortex in the brain

Optic Chiasm

Point in the brain where the optic nerve fibers from each eye meet and partly cross over to the opposite side of the brain

Trichormatic theory of color vision

The theory that the sensation of color results because of the cones in the retina are especially sensitive to either red light, green light,or blue light

Color blindness

One of several inherited forms of color deficiency or weakness in which an individual cannot distinguish between certain colors

Afterimage

A visual experience that occurs after the original source of stimulation is no longer present

Opponent-process theory of color vision

The theory that color vision is the product of opposing pairs of color receptors, red/green, blue/yellow, and black/white; when one member of color pair is stimulated the other is not

Audition

The technical term for hearing

Loudness

The intensity (or amplitude) of a sound wave, measured in decibels

Amplitude

The intensity or amount of energy of a wave, reflected In the height of the wave; the amplitude of a sound determines loudness

Decibel

The unit of measurement for loudness

Pitch

The relative highness or lowness of a sound, determined by the frequency of a sound wave.

Frequency

The rate of vibration, or the number of sound waves per second

Timbre

The distinctive quality of a sound, determined by the complexity of a sound wave

Outer Ear

The part of the ear that collects sound waves; consists of the pinna, the ear canal, and the eardrum

Eardrum

A tightly stretched membrane at the end of the ear canal that vibrates when hit by sound wave

Middle ear

The part of the ear that amplifies sound waves, consist of three small bones, the hammer, the anvil, and the stirrup

Inner Ear

The part of the ear where sound is transduced into neural impulses; consist of the cochlea and semicircular canals

Cochlea

The coiled, fluid-filled inner-ear structure that contains the sensory receptors for sound

Basilar Membrane

The membrane within the cochlea of the ear that contains the hair cells

Hair cells

The hair like sensory receptors for sound, found in the basilar membrane of the cochlea

Frequency theory

The view that the basilar membrane vibrates at the same frequency as the sound wave

Place theory

The view that different frequencies cause larger vibrations at different locations along the basilar membrane

Olfaction

Technical name for the sense smell

Gustation

Technical name for the sense of taste.

Olfactory bulb

The enlarged ending of the olfactory cortex at the front of the brain where the sensation of smell is registered

Pheromones

Chemical signals released by an animal that communicates information and affect the behavior of other animals of the same species

Taste buds

The specialized sensory receptors for taste that are located on the tongue and inside the mouth and throat

Pain

The unpleasant sensation of physical discomfort or suffering that can occur in varying degrees of intensity

Gate-control theory

The theory that pain is a product of both physiological and psychological factors that cause spinal gates to open and relay patterns of intense stimulation to the brain, which perceives them as pain.

Substance P

A neurotransmitter that is involved in the transmission of pain messages to the brain

Kinesthetic sense

The technical name for the sense of location and position of body parts in relation to one another

Proprioceptros

Sensory receptors, located in the muscles and joints, that provide information about body position and movement.

Vestibular sense

The technical name for the sense of balance, or equilibrium.

ESP (extrasensory perception)

Perception of information by some means other than through the normal process of sensation

Parapsychology

The scientific investigation of claims of paranormal phenomena and abilities

Bottom-up processing

Information processing that emphasizes the importance of the sensory receptors in detecting the basic features of a stimulus in the process of recognizing a whole pattern; also called data-driven processing

Top-down processing

Information processing that emphasizes the importance of the observer’s knowledge, exceptions, and other cognitive processes, in arriving at meaningful perception; analysis that moves from the whole parts; also called conceptually driven processing

Gestalt psychology

a school of psychology founded in Germany in the early 1900s that maintained that our sensations are actively processed according to consistent perceptual rules that result in meaningful whole perceptions

Figure-ground relationship

A Gestalt principle of perceptual organization that states that we automatically separate the elements of a perception into the feature that clearly stands out and its less distinct in the background

Depth perception

The use of visual cues to perceive the distance or three-dimensional characteristics of objects

Monocular cues

Distance or depth cues that can be processed by either eye alone

Binocular cues

distances or depth cues that require the use of both eyes

Perceptual cues

The tendency to perceive objects, especially familiar objects, as constant and unchanging despite changes in sensory input

Size constancy

The perception of an object as maintaining the same shape regardless of the image produced on the retina

Shape constancy

The perception of an object as maintaining the same shape regardless of the image produced on the retina

Brightness constancy

The perception that the brightness of an object remains the same even though the lighting conditions change

Perceptual illusion

The misperceptions of the true characteristics of an object or an image

Muller-Lyer Illusion

A famous visual illusion involving the misperception of the identical length of two lines, one with an arrow pointed inward, one with an arrow pointed outwards

Moon illusion

A visual involving the misperception that the moon is larger when it is on the horizon than when is directly overhead

Perceptual set

the influence of prior assumptions and exceptions on perceptual interpretations.

KEY PEOPLE

Karl Duncker

German Gestalt psychologist who is best known for his studies on the perception of motion; also studies the perception of pain and the effect of past experience on perception.

Max Wertheimer

German psychologist who founded Gestalt psychology in the early 1900s, immigrated to the United States in 1933, studied the optical illusion of apparent movement, and described principles of perception