The body receives information through the five main senses.

The Five Human SensesHearing

Vision Taste

Smell

Touch

Sensation

a process by which our sensory receptors and nervous system receive and represent stimulus energy

Perception

a process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events

Sensation

Bottom-Up Processing

analysis that begins with the sense receptors and works up to the brain’s integration of sensory information

Top-Down Processing

information processing guided by higher-level mental processes

as when we construct perceptions drawing on our experience and expectations

Sensation

Our sensory and perceptual processes work together to help us sort out complex processes

How Many Wolves?

Psychophysics

study of the relationship between physical characteristics of stimuli and our psychological experience of them

Light- brightness

Sound- volume

Pressure- weight

Taste- sweetness

Sensation - Basic Principles

Absolute Threshold

minimum stimulation needed to detect a particular stimulus 50% of the time

Difference Threshold

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

just noticeable difference (JND)

Sensation - Threshold

An absolute threshold is the minimal amount of sensory stimulation needed for a sensation to occur.

Signal Detection Theory

predicts how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise)

assumes that there is no single absolute threshold

detection depends partly on person’s

experience

expectations

motivation

level of fatigue

Subliminal

When stimuli are below one’s absolute threshold for conscious awareness

0

25

50

75

100

Low Absolutethreshold

Medium

Intensity of stimulus

Percentageof correctdetections

Subliminal stimuli

Subliminal Messages

Subliminals?

Subliminals?

Weber’s Law- to perceive as different, two stimuli must differ by a constant minimum percentage

light intensity- 8%

weight- 2%

tone frequency- 0.3%

Sensory adaptation- diminished sensitivity as a consequence of constant stimulation

Sensation

Transduction

conversion of one form of energy to another

in sensation, transforming of stimulus energies into neural impulses

Wavelength

the distance from the peak of one wave to the peak of the next

Vision

Hue

dimension of color determined by wavelength of light

Intensity

amount of energy in a wave determined by amplitude

brightness

loudness

Vision

Short wavelength=high frequency(bluish colors, high-pitched sounds)

Long wavelength=low frequency(reddish colors, low-pitched sounds)

Great amplitude(bright colors, loud sounds)

Small amplitude(dull colors, soft sounds)

Vision-Physical

Light: The Visual Stimulus

Light can be described as both a particle and a wave

Wavelength of a light is the distance of one complete cycle of the wave

Visible light has wavelengths from about 400nm to 700nm

Wavelength of light is related to its perceived color

The spectrum of electromagnetic energy

Vision Cornea– the outer covering of the eye

Pupil- adjustable opening in the center of the eye

Vision Iris- a ring of muscle that forms the

colored portion of the eye around the pupil and controls the size of the pupil opening

Lens- transparent structure behind pupil that changes shape to focus images on the retina

(like camera lens)

Vision

Vision Accommodation- the process by which

the eye’s lens changes shape to help focus near or far objects on the retina

Retina- the light-sensitive inner surface of the eye, containing receptor rods and cones plus layers of neurons that begin the processing of visual information

Vision Acuity- the sharpness of vision Nearsightedness- condition in which

nearby objects are seen more clearly than distant objects because distant objects in front of retina

Farsightedness- condition in which faraway objects are seen more clearly than near objects because the image of near objects is focused behind retina

Vision

Farsighted Nearsighted Normal Vision Vision Vision

Retina’s Reaction to Light- Receptors Rods

peripheral retina detect black, white and gray twilight or low light

Cones near center of retina fine detail and color vision daylight or well-lit conditions

Color Vision Our visual system interprets differences

in the wavelength of light as color Rods are color blind, but with the cones

we can see different colors This difference occurs because we

have only one type of rod but three types of cones

Retina’s Reaction to Light

Optic nerve- nerve that carries neural impulses from the eye to the brain

Blind Spot- point at which the optic nerve leaves the eye, creating a “blind spot” because there are no receptor cells located there

Fovea- central point in the retina, around which the eye’s cones cluster

Blindspot

Vision- ReceptorsReceptors in the Human Eye

Cones Rods

Number

Location in retina

Sensitivity in dim light

Color sensitive? Yes

Low

Center

6 million

No

High

Periphery

120 million

Rods

Cones

Processing Visual Information

Ganglion cells— neurons that connect to the bipolar cells, their axons form the optic nerve

Bipolar cells— neurons that connect rods and cones to the ganglion cells

Optic chiasm— point in the brain where the optic nerves from each eye meet and partly crossover to opposite sides of the brain

Visual Pathway

Axons of the ganglion cells come together to form the optic nerve

Half of optic nerve fibers cross into opposite hemisphere and synapse onto LGN (lateral geniculate nucleus)

LGN neurons synapse onto primary visual cortex

Pathways from the Eyes to the Visual Cortex

Feature Detectors

nerve cells in the brain that respond to specific features

shape

angle

movement

Stimulus

Cell’s responses

Visual Information Processing

How The Brain Perceives

The Necker Cube

Illusory Contours

Parallel Processing

simultaneous processing of several aspects of a problem simultaneously

Visual Information

Color Mixing

Two basic types of color mixingsubtractive color mixture

example: combining different color paintsadditive color mixture

example: combining different color lights

Additive Color Mixture By combining lights

of different wavelengths we can create the perception of new colors

Examples:red + green = yellowred + blue = purplegreen + blue = cyan

Trichromatic Theory of Color Vision

Researchers found that by mixing only three primary lights (usually red, green and blue), they could create the perceptual experience of all possible colors

This led Young and Helmholtz to propose that we have three different types of photoreceptors, each most sensitive to a different range of wavelengths

Visual Information Processing Trichromatic (three color) Theory

Young and Helmholtz three different retinal color receptors

red green blue

Color Vision

Some people cannot tell the difference between certain colors. The most common form is the inability to see the colors of red or green.

People who suffer red-green blindness have trouble perceiving the number within the design

Color-Deficient Vision

Opponent Process Theory of Color Vision

Some aspects of our color perception are difficult to explain by the trichromatic theory alone

Example: afterimagesif we view colored stimuli for an

extended period of time, we will see an afterimage in a complementary color

Color Blindness

Visual Information Processing

Opponent-Process Theory- opposing retinal processes enable color vision

“ON” “OFF”

red green

green red

blue yellow

yellow blue

black white

white black

Opponent Process- After Image

Complimentary-After Image

Opponent-Process Theory To account for phenomena like

complementary afterimages, Herring proposed that we have two types of color opponent cellsred-green opponent cellsblue-yellow opponent cells

Our current view of color vision is that

it is based on both the trichromatic and opponent process theory

Color Constancy

Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

Visual Information Processing

Overview of Visual SystemOverview of Visual System

• The eye is like a camera, but instead of using film to catch the light we have rods and cones

• Cones allow us to see fine spatial detail and color, but cannot function well in dim light

• Rods enable us to see in dim light, but at the loss of color and fine spatial detail

• Our color vision is based on the presence of 3 types of cones, each maximally sensitive to a different range of wavelengths

Audition Audition

the sense of hearing Frequency

the number of complete wavelengths that pass a point in a given time

Pitch a tone’s highness or lowness depends on frequency

The Intensity of Some Common Sounds

Audition- The Ear Outer Ear

ear lob and auditory canal Middle Ear

chamber between eardrum and cochlea containing three tiny bones (hammer, anvil, stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window

Audition- The Ear Inner Ear

innermost part of the ear, continuing the cochlea, semicircular canals, and vestibular sacs

Cochlea coiled, bony, fluid-filled tube in the inner

ear through which

Transduction of Sounds

The structures of the ear transform changes in air pressure (sound waves) into vibrations of the Basilar Membrane

As the Basilar Membrane vibrates it causes the hairs in the Hair Cells to bend

The bending of the hairs leads to a change in the electrical potential within the cell

Audition Place Theory

the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated

Frequency Theory 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

How We Locate Sounds

Audition

Conduction Hearing Loss hearing loss caused by damage to the

mechanical system that conducts sound waves to the cochlea

Nerve Hearing Loss hearing loss caused by damage to the

cochlea’s receptor cells or to the auditory nerve

Audition Older people tend to hear low

frequencies well but suffer hearing loss for high frequencies

1time

10times

100times

1000times

32 64 128 256 512 1024 2048 4096 8192 16384

Frequency of tone in waves per second

Low Pitch High

Amplitude required forperception relative to 20-29 year-old group

Chemical and Body Senses

• Olfaction (smell)• Gustation (taste)• Touch and temperature• Pain• Kinesthetic (location of body)• Vestibular (balance)

TouchTouch Skin Skin

SensationsSensations pressurepressure

only skin only skin sensation with sensation with identifiable identifiable receptorsreceptors

warmthwarmth coldcold painpain

Pain Gate-Control Theory (Melzack & Wall)

theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain

“gate” opened by the activity of pain signals traveling up small nerve fibers

“gate” closed by activity in larger fibers or by information coming from the brain

TasteTaste Taste SensationsTaste Sensations

sweetsweet soursour saltysalty bitterbitter

Sensory InteractionSensory Interaction the principle that one sense may the principle that one sense may

influence anotherinfluence another as when the smell of food influences its as when the smell of food influences its

tastetaste

Taste

• Sweet

• Sour

• Salty

• Bitter

Smell

Receptor cells inolfactory membrane

Nasal passage

Olfactorybulb

Olfactorynerve

Age, Sex and Sense of Smell

Women

Men

10-19 20-29 30-39 40-49 50-59 60-69 70-79 80-89 90-99Age Group

4

3

2

0

Numberof correct

answers

Women and young adults have best sense of smell

Body Position and Body Position and MovementMovement

KinesthesisKinesthesis the system for sensing the position the system for sensing the position

and movement of individual body and movement of individual body partsparts

Vestibular SenseVestibular Sense the sense of body movement and the sense of body movement and

positionposition including the sense of balanceincluding the sense of balance