Sensation and Perception

Sensation

Sensation

Exploring through the sences

Perception

organizing and interpreting sensory information

Bottom-up processing

begins with the senses and works up (sensation)

Top-down processing

view things based on experience or expectations and work down

Selective attention

focusing on a particular stimulus (one TV at a time)

Cocktail party effect

focusing on one voice among many (type of selective attention)

Inattentional blindness

failing to see things because our attention is focused elsewhere

Change blindness

failing to notice changes in the environment (person giving directions)

Absolute threshold

the minimum stimulation needed to detect something 50 percent of the time (ex. Candle 30 miles away)—subliminal messages are below our absolute threshold

Difference threshold

the minimum it takes to detect difference between two things (also called just noticeable difference (jnd))

Weber’s law

things must differ by a percentage rather than an amount (quarter in shoe, candy bar)

Signal detection theory

detecting something based on experience, expectation, or motivation (ex. Baby’s cry, cell phone)

Sensory adaptation

diminished sensitivity to something (cold pool becomes warm)

Transduction

process of changing what we see into neural impulses

Cornea

protective covering

Pupil

opening in eye…where light enters

Iris

colored muscle around pupil…adjusts the light that enters eye

Lens

focuses images

Retina

contains rods and cones

Rods

see black and white

Cones

see color

Fovea

central focal point, where cones cluster

Bipolar Cells

Connect rods and cones to ganglion cells

Ganglion cells

Collect visual info and send to brain

Nearsightedness

can see close up, light focuses in front of retina

Farsightedness

can see far away, light focuses behind retina

Optic nerve

carries information from the eye to the brain

Blind spot

part where optic nerve leaves the eye…no cones or rods there

Feature detectors

respond to shape, angle and movement (Hubel and Wiesel)

Parallel processing

processing many things at once (color, motion, form…)

Young Helmholtz trichromatic theory

we have cones for red, green, and blue that mix to give all the combinations (subtractive is paint so it is black…additive is light and is white)

Opponent process theory

we have opposing pairs (red/green, yellow/blue, black/white) and when one wears out the other takes over (after image effect)

Audition

sense of hearing

Decibels

how we measure sound (0 is absolute threshold, above 85 can cause damage)

Outer ear

visible part (pinna) and auditory canal

Middle ear

three tiny bones (anvil, hammer, stirrup... aka ossicles

Inner ear (oval window)

contains cochlea, semicircular canals, and vestibular sacs

Cochlea

coiled, fluid filled tube in that triggers nerve impulses

Basilar membrane (middle of cochlea)

contains hair cells…fluid hits here

Place theory

depends on where the sound waves hit along the basilar membrane…best for high pitches

Frequency theory

the rate of impulses going up the auditory nerve matches the tone…better for low-pitched sounds

sound localization

we can locate sounds based on which ear they strike first

Conduction hearing loss

eardrum is punctured

Sensorineural hearing loss

damage to hair cells…comes from loud sounds or age (hearing aid or cochlear implant may help)

Taste (gustation) and smell (olfaction)

referred to as chemical senses

Olfactory bulbs

We smell with them

Sensory interaction

one sense influences another (smell and taste)

Skin senses

touch, pressure, temperature, pain

Kinesthetic sense

sensing and moving your body parts...knowing where your arm is

• Receptors in muscles, tendons, and joints

Vestibular sense

body position and movement, our sense of balance

• Receptors are located in the inner ear (semicircular canals and otolith organs)

Phantom limb sensations

sensations that come even when a limb is missing

Gate-control theory

The spinal cord contains a gate that either allows or blocks pain signals

Gestalt

an organized whole…the whole is greater than the sum of its parts (Gestalt Psychology)

Figure-ground

what you are looking at becomes your figure, the rest is the ground

Similarity

group things that are similar

Proximity

group things by how close together they are

Closure

fill in the gaps to make something look whole

Connectedness

group things by how connected they are

Continuity

we perceive smooth, continuous patterns

Size constancy

knowing the size of something doesn’t change (looking at homes from a plane)

Shape constancy

knowing that the shape doesn’t change

Lightness (color) constancy

knowing that something is the same color even when the lighting changes

Relative size

things that are closer look bigger

Interposition (overlap)

when one thing blocks another, it has to be closer

Texture gradient

the more detail something has, the closer it looks

Relative height

objects higher in the visual field look farther away

Relative clarity (aerial perspective)

distant objects are more hazy

Linear perspective

parallel lines seem to come together in the distance

Relative motion (motion parallax)

things below your field of vision look like they are moving backward and faster

Binocular cues

use two eyes (retinal disparity and convergence)

Retinal disparity (binocular disparity)

the difference in the images produced by your two eyes (retinal sausage)

Convergence

tendency for eyes to turn inward when looking at something close

Visual cliff

used to measure baby’s depth perception

Phi phenomenon

when lights turn on and off, it creates the sense of movement

Stroboscopic motion

“flip book”, looks like it creates movement

Perceptual set

a mental predisposition to perceive something one way or the other

Context effects

the context that we see something in alters our perception of it

Muller-Lyer illusion

we live in a perfectly carpentered world

Perceptual adaptation

we adapt to a changed visual input (basketball player with goggles)

ESP

extrasensory perception

Telepathy

mind to mind

Clairvoyance

perceiving remote events (thinking your house is on fire now)

Precognition

seeing future events (predicting 9/11)