Chapter 4:

Sensation and Perception

Sensory Systems: The First Step

How Do Sensory Systems Function?

• Primary function of the senses is to act as biological transducers

• Sensation • Perception• Transduction

Vision

• Visible Spectrum– Part of the

electromagnetic spectrum to which the eyes respond

– Hue– Saturation – Brightness

Structure of the Eye

Vision: Rods and Vision: Rods and ConesCones • Two types of Two types of

photoreceptors photoreceptors located in retinalocated in retina– Cones:Cones:

• Have 6.5 millionHave 6.5 million

• Visual receptors for Visual receptors for bright light (daylight) bright light (daylight)

• Color visionColor vision

– Rods:Rods: • Have 100 millionHave 100 million

• Visual receptors for dim Visual receptors for dim lightlight

• Black and whiteBlack and white

Vision: ColorVision: Color• Trichromatic Trichromatic

TheoryTheory – Color vision Color vision

theory that theory that states we have states we have three cone types: three cone types: red, green, bluered, green, blue

– Other colors Other colors produced by a produced by a combination of combination of thesethese

– Black and white Black and white produced by rodsproduced by rods

Vision: Color• Opponent Process Theory • Color vision theory based on three opponent “systems”:

– Red/green; Blue/yellow; black/white

• Exciting one color in a pair (red) blocks the excitation in the other member of the pair (green)

• Afterimage: – Visual sensation that remains after stimulus is removed

Hearing: Structure of Hearing: Structure of the Earthe Ear

• Outer and Middle Ear– Pinna:

• Visible, external part of the ear

– Tympanic Membrane: • Eardrum

– Auditory Ossicles: • Three small bones that

vibrate• link eardrum with the

cochlea• Malleus (hammer)• Incus (anvil)• Stapes (stirrup)

Hearing: Structure of Hearing: Structure of the Earthe Ear

• Inner Ear– Cochlea:

• Snail-shaped• Organ of hearing

– Hair Cells: • Receptor cells within

cochlea • Transduce vibrations

into nerve impulses• Once dead they are

never replaced

– Organ of Corti: • Center part of the

cochlea containing hair cells, canals, and membranes

HearingHearing• Sound Waves:Sound Waves:

– Rhythmic Rhythmic movement of air movement of air moleculesmolecules

– Rarefaction and Rarefaction and compressioncompression

– FrequencyFrequency– AmplitudeAmplitude

Hearing: Detecting Higher and Lower Sounds

• Frequency Theory: – As pitch rises, nerve

impulses of the same frequency flow into the auditory nerve: also known as the “piano theory”

• Place Theory: – Higher and lower tones

excite specific areas of the cochlea: also known as the “microphone theory”

Hearing LossHearing LossConduction Hearing LossConduction Hearing LossPoor transfer of sounds from tympanic membrane to the inner earCompensate with hearing aid

Sensorineural Hearing Sensorineural Hearing LossLossCaused by damage to inner ear hair cells or auditory nerve

– Hearing aids useless; auditory messages cannot reach brain

– Cochlear Implant: • Electronic device that stimulates

auditory nerves

Stimulation DeafnessStimulation DeafnessDamage caused by exposing hair cells to excessively loud sounds

• Typical at rock concerts• By age 65, 40% of hair cells are gone

The Sense of SmellThe Sense of SmellOlfactionOlfactionA chemical senseA chemical sense

The RouteThe RouteNerve EndingsNerve Endings to to The NeuronsThe Neurons to to The Olfactory BulbThe Olfactory Bulb to to The Limbic The Limbic SystemSystem

The Lock & Key The Lock & Key TheoryTheory

5 Odors Identified5 Odors IdentifiedFloral, Camphoric, Musky, Minty, & Floral, Camphoric, Musky, Minty, & EtherishEtherish

TasteTasteGustationGustationA Chemical SenseA Chemical Sense

The RouteThe RouteThe Tongue The Tongue toto The The Papillae Papillae toto The Taste Buds The Taste Buds toto The Brain The Brain

5 Tastes 5 Tastes IdentifiedIdentifiedSweet, Sour, Salty, Bitter, Sweet, Sour, Salty, Bitter, & Umami& Umami

Grace and BalanceGrace and Balance

The Kinesthetic The Kinesthetic SenseSenseKeeps us informed about Keeps us informed about movement of body parts & movement of body parts & their position in relation to their position in relation to each other.each other.Muscle Movement, Posture, Muscle Movement, Posture, & Joints& JointsInformation comes from Information comes from stretch receptors, the stretch receptors, the tendons, & the internal tendons, & the internal organs.organs.

Balance & EquilibriumBalance & Equilibrium

Vestibular Vestibular SenseSenseThe Vestibular Sense keeps us informed about balance & the position of our body in space.Hair cells in the inner ear bend in Hair cells in the inner ear bend in relation to the position & relation to the position & movement of the head giving movement of the head giving information that the brain uses to information that the brain uses to help us maintain our balance and help us maintain our balance and to sense changes in our movement to sense changes in our movement through space.through space.

The Tactile SensesThe Tactile Senses

TouchTouchSkin receptors that make us aware of how & where we’re being touched.

PressurePressureReceptors beneath the skin that make us aware of deeper touch.

TemperatureTemperatureReceptors are found just beneath the skin to give the sensation of hot, cold, and warm.

The Tactile SensesThe Tactile Senses

PPaaiinnPain is adaptive & lets us know there’s something wrong.Pain receptors are located not just in the skin, but also in other parts of the body: muscles, joints, ligaments, teeth, & the internal organs.

2 Kinds of Pain2 Kinds of PainDull (slow) painLong axonsSharp (fast) painShort axons

The Gate The Gate Control Theory Control Theory of Painof PainThere is a “neurological gate” There is a “neurological gate” in the spinal cord controlling in the spinal cord controlling the transmission of pain the transmission of pain messages to the brain.messages to the brain.Dull, throbbing pain is conducted through the gate by thinner & slower nerve fibers that carry signals for touch & temperature.Faster, thicker nerve fibers cause a bottleneck at the gate, blocking the passage of other messages.

Perceiving Perceiving RealityReality

Apparent Apparent MotionMotion The Autokinetic EffectThe Autokinetic EffectApparent motion of a single light in Apparent motion of a single light in total darkness.total darkness.

The Phi PhenomenonThe Phi PhenomenonA series of blinking lights.A series of blinking lights.

The Stroboscopic The Stroboscopic EffectEffectThe “jerky” effect of a strobe light The “jerky” effect of a strobe light blinking in total darkness with blinking in total darkness with movement.movement.

Perceptual Organizational PrinciplesPerceptual Organizational Principles

Figure – GroundFigure – Ground The simplest type of The simplest type of

organizational principleorganizational principle

Reversible Figure-GroundReversible Figure-Ground

Unclear Figure-GroundUnclear Figure-Ground

Illusory Figure-GroundIllusory Figure-Ground

Filling in the GapsFilling in the Gaps

ClosureClosureThe tendency to perceive an object The tendency to perceive an object or shape even when the form isn’t or shape even when the form isn’t complete.complete.

Perceiving Depth & Perceiving Depth & DistanceDistance

SimilaritySimilaritySimilar objects are Similar objects are perceived as being perceived as being together.together.

ProximityProximityStimuli close together are Stimuli close together are perceived as being perceived as being together.together.

Perceiving Depth & Perceiving Depth & DistanceDistance

InterpositionInterpositionSomething is placed between Something is placed between the eye and the object.the eye and the object.

Texture GradientTexture GradientTextured objects further away Textured objects further away look smooth.look smooth.

Perceiving Depth & Perceiving Depth & DistanceDistance

Linear PerspectiveLinear PerspectiveConvergence of lines or the Convergence of lines or the vanishing point in art. vanishing point in art.

Aerial PerspectiveAerial Perspective Close objects appear clearer Close objects appear clearer than those farther away.than those farther away.

Perceiving Depth & Perceiving Depth & DistanceDistance

Motion ParalaxMotion ParalaxCloser objects seem to move Closer objects seem to move faster than those farther away faster than those farther away when in motion.when in motion.

Light and Light and ShadowShadowGives objects the appearance of Gives objects the appearance of three dimensions.three dimensions.

Perceiving Depth & Perceiving Depth & DistanceDistance

Relative SizeRelative SizeThe smaller the image of an object is on the retina, the farther away it seems.

Relative HeightRelative HeightObjects higher in the visual field are perceived as farther away.

The Optic ChiasmThe Optic ChiasmPoint in the temporal Point in the temporal area of the brain where area of the brain where the optic nerve crosses the optic nerve crosses over from left to right.over from left to right.This is where stereo vision is This is where stereo vision is created.created.

Stereoscopic VisionStereoscopic Vision

Seeing the world in Three-DimensionsSeeing the world in Three-Dimensions

Binocular cues:Binocular cues:Retinal DisparityRetinal Disparity

The difference between the two eyes

ConvergenceConvergence

The eyes focusing close up

Stereoscopic VisionStereoscopic Vision

Seeing depth naturally

Perceptual ConstanciesPerceptual Constancies

Size ConstancySize ConstancyObjects continue to remain the same size no matter how distant.

Shape ConstancyShape ConstancyObjects remain the same shape even if the image on the retina shows a different shape.

Color ConstancyColor ConstancyInfluenced by lighting (artificial, colored, or natural).

Visual IllusionsVisual Illusions

More IllusionsMore Illusions

More IllusionsMore Illusions

Subliminal PerceptionSubliminal Perception

Stimulation Stimulation below the below the threshold of threshold of conscious conscious awareness.awareness.There is no evidence to support There is no evidence to support subliminal perception subliminal perception occurring.occurring.

Reverse MaskingReverse MaskingThere is no evidence to support There is no evidence to support reverse masking causes reverse masking causes subliminal or any other subliminal or any other stimulation.stimulation.