Unit 4 - Sensation and Perception

Bottom-Up Processing

Bottom-Up Processing

- analysis that begins with the sensory receptors and works up to the brain's integration of sensory information
- body to brain

Top-Down Processing

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

Selective Attention (cocktail party effect)

- the focusing of conscious awareness on a particular stimulus
- the ability to focus awareness on a small segment of information that is available through our sensory systems

Inattentional Blindness

- failing to see visible objects when our attention is directed elsewhere

Change Blindness

- failing to notice changes in the environment
- a form of inattentional blindness

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

Absolute Threshold

- the minimum stimulation needed to detect a particular stimulus 50 percent of the time
- the minimum intensity of stimulation that must occur before you experience a sensation
- ex: 50% of people can taste one tsp of sugar in 2 gallons of water

Gustav Fechner

- 1801-1887
- Field: perception
- Contributions: stated that the magnitude of a sensory experience is proportionate to the # of JND's that the stimulus causing the experiences above the absolute threshold

Difference Threshold (JND)

- the minimum difference between two stimuli required for detection 50% of the time

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
- after constant exposure, nerve cells fire less frequently

Perceptual Set

- a mental predisposition to perceive one thing and not another

Context Effects

- memory is aided by being in the physical location where encoding took place
- describes how the context in which a stimulus occurs can contribute to how people perceive that stimulus

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 _____ 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

Blind Spot

- the point at which the optic nerve leaves the eye and no receptor cells are located there

Young-Helmholtz Trichromatic Theory

- visual theory, stated by Young and Helmholtz that all colors can be made by mixing the three basic colors: red, green, and blue

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

Feature Detectors

- nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement
- lack of development of the _________ makes small children unable to color within lines

Gestalt Principles

- describe the top-down processing that organizes sensory information into distinct forms
- principles that describe the brain's organization of sensory information into meaningful units and patterns
- six principles: nearness, similarity, common region, closure, continuity, and figure & ground

Figure-Ground

- the organization of the visual field into objects that stand out from their surroundings

Grouping

- the perceptual tendency to organize stimuli into coherent groups

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

Monocular Cues

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

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 through which sound waves trigger nerve impulses

Inner Ear

- the innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs
- vibrations in the cochlea jostles the fluid and the hair cells lining its surface

Sensorineural Hearing Loss

- hearing loss caused by damage to the cochlea's receptor cells or to the auditory nerves
- within the inner ear, damage to the stereocilia
- also called nerve deafness
- preventable

Conduction Hearing Loss

- less common form of hearing loss caused by damage to the mechanical system (eardrum and bones in middle ear) that conducts sound waves to the cochlea
- infection, tumors, head injuries

Place Theory

- 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

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

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
- comes from sensors in your joints, tendons, bones, and skin

Vestibular Sense

- the sense of body movement and position, including the sense of balance
- comes from hair like receptors in the semi-circular canals & the vestibular sacs connected to the cochlea

Synesthesia

- when one kind of sensory stimulus evokes the subjective experience of another