Sensation and Perception

Chapter 5

Threshold

Detecting vs. not detectingCan you hear it, taste it, see it or not?Ex. Grade school hearing test

Absolute thresholdSmallest amount of energy that will produce a sensationEx. Eye chart determines vision

Difference threshold

Smallest change in a stimulus that produces a change

Just noticeably differentEx. 3 lb package in empty

vs. full backpackEx. Darkroom, turn on

light, appears bright

Weber’s law

Larger or stronger a stimulus, larger the change required for observer to notice

Ex. Yell in empty stadium vs. packer game

Sensory adaptation

Adapt to constant level of stimuliGet used to new level, respond only to change

Ex. Eyes in a movie theaterWithout adaptation, senses would be bombarded

Senses

VisionHearingSmellTasteTouchTemperaturePainVestibularkinesthesis

Kinesthesis

Movement and body positionWithout, movements would

be jerky1st affected by alcoholEx. Touch nose, heel toe

Vestibular

Motion and balanceUtricle – detects linear motionSemicircular canal – rotary regulated by inner earRollercoaster fun or sickeningOverstimulation causes dizzinesslocated in ear, but linked to vision

Vestibular nystagmus

Eyes go through a rotary spasm after spinning2nd sense affected by alcoholHorizontal gaze nystagmusVertical gaze nystagmusvideo

http://www.opt.uab.edu/emweb/Nystagmus.htm

Motion sickness

Disagreement between vision and vestibular sense

Plane – vestibular feels speed, but eyes see nothing

Car – vestibular feels speed, but eyes see different

Boat – unpredictable rates

Receptors of Skin

PainColdHeatTouch

TouchReceptor – mechanical sensors send electric signals to the somatosensory cortex

Touch ContinueSkin – largest organ containing sensors

Layers of Skin

Epidermis – dead skin, no receptors

Dermis – contain variety of receptors including hair receptors

Fatty layer – pacinian corpusoleHighly sensitive to touch

Hair receptors

Nerve endings wrapped around the base of each hair follicleAdaptation – when hair remains bentFree nerve endings – give info. about temperature and pain

Pain

Caused byTissue damageAttentional stateDoing something else, don’t noticeEmotional stateWhen afraid, hurts moreReceptor – send nerve impulses to the somatosensory and limbic area of the brainEndorphins – natural painkiller

Nerve ending in finger send info along spinal cordThe neurons travel up the spinal cord then form synapses with neurons in the thalamus (magenta circle)The thalamus organizes info and sends to sensory cortex (blue)

Interprets the information as pain Sends info to motor cortex (orange)Motor cortex (orange) sends info. back to the thalamus (green pathway)Thalamus organizes incoming info. and sends signals down the spinal cordReact to the pain (e.g., shaking the finger or screaming "ouch!").

Pain contined

Pain tolerance – ability to handle painReferred pain – pain in an area away from the sourceEx. Headache may stem from backpain

Temperature

Stimulus – change in temperature on skinReceptor – skin and hair folliclesThermoadaptationShort-term – bathtubLong-term – go to Florida in winter

Taste

Stimulus – chemicals of the substance mixing with salivaReceptors – taste budsSweetSaltySourBitterUmami – meaty-cheese tasteParmasan cheese, fish, meat

Taste buds

Couple of drops of blue food coloring

http://biology.about.com/library/organs/blpathodigest2.htm?terms=digestive+system+activity

Taste buds

Taste buds

Amount inherited – 500-10,000Sends messages to the parietal lobe

Other factors for Taste

SmellTemperatureTextureAppearanceColor

Taste Continued

If one changes, all change in opposite directionEx. Drink orange juice after brushing teethTaste lossSmokingAge – lose 30% by age 20AdaptationKeep adding salt to fries

Smell

Receptor – olfacotry epithelium

Smell and memory

Transduction -Transforms chemical reaction into a nerve impulseNerves from the olfactory bulb make connections with the limbic systemThe limbic system contains the hypothalamus, the hippocampus, and the amygdalaResponsible for our emotions and in the formation of memories.

Loss of smell

Virus destroys receptorsDamage to the neurons

Functions of smell

Potential dangerFire, gas, spoiled foodMemoryChoosing a matePheromones

Adaptation of smell

Short-termLeave room, come back and it smellsLong-termSignificant odors in your lifePeople with B.O. can’t smell themselves

Auditory anatomy

Outer earPinna – cartilage covered with skin on both sides of your head “ears”External auditory canalNothing smaller than an elbow should enterContains wax and hair to keep dirt out

http://www.brainconnection.com/topics/?main=anat/auditory-anat

Middle ear

Ear drum – vibrates messages to the fluid of the cochlea

Middle ear

OssiclesMalleus (hammer)Inca (anvil)Stapes (stirup)

Ability to freezeEustachian tube – Equalizes pressure

Inner ear (size of pea)

Cochlea – filled with fluid and hair cellsPick up vibrations from oval windowOrgans of corti – stiff membrane that moves against the hair cells to produce soundEars ringing – permanent hearing lossSemicircular canal – controls balance

After 120 decibels of noise – equivalent of rock concert

Healthy Damaged

http://concise.britannica.com/ebc/art-529

Perception

interpretation of what we take in through our senses

Perceptual Organization

Similarity Proximity Continuity Closure

Similarity

Objects that look similar appear to go together

Back

Proximity

Objects that are close together appear to go together

Back

Continuity

Lines are seen as following the smoothest path

Back

Closure

We tend to ignore gaps and fill in the missing lines

Back

Figure-Ground

Puts the visual scene into a figure that we look at and a ground which is everything else and forms the background

Constancy

SizeShapeBrightnessColor

Size Constancy

Ability to see objects further away as same size

Shape Constancy

Color constancy

The ability to see color regardless of changing conditions.

Brightness Constancy

ability to see objects as having the same brightness even though light may change their immediate sensory properties

Depth Perception

Monocular cues – need only one eyeBinocular cues – need 2 eyes

Monocular cues

InterpositionLinear perspectiveElevationTexture gradientMotion parallax

Interposition

One object appears to be blocking another

Linear Perspective

Visual field appears to come to a point

Elevation

Objects further away appear to get higher

Texture gradient

Objects closer have more detail than objects further away

Motion Parallax

Objects close to us seem to move faster than objects further awayEx. Fingers vs. boardEx. Plane vs. car

http://psych.hanover.edu/Krantz/MotionParallax/MotionParallax.html

Binocular Cues

Retinal DisparityImages on the retina are in different places on the eyeClose one eye and pencilConvergence as objects get farther from our face they convergePencil move toward face

Illusions

Phenomenon which what you see is not actually what is presentMoon illusionHorizontal-vertical illusionMueller-lyerPonzoPaggendorffHering

Moon illusion

Mueller-lyer illusion

Due to closure

Ponzo

Poggendorff

Larger the angle, more illusion

Herings illusion

Afterimage

Color theory – black and white cones become overstimulated and causes afterimage

After image

After image

Illusions

http://home.earthlink.net/~toddwolly/vision/fun.html