Myers’ PSYCHOLOGY

Chapter 5

Sensation

Sensation and Perception

Sensation a process by which our sensory receptors and

nervous system receive and interpret stimulus energy

After receiving sensory information we must process it and this is perception

Perception a process of organizing and interpreting

sensory information, enabling us to recognize meaningful objects and events

Sensation and perception blend into one continuous process

Sensation

Bottom-Up Processing analysis that begins with the sense receptors and

works up to the brain’s integration of sensory information

Detects lines, angles, and colors

Top-Down Processing information processing guided by higher-level

mental processes as when we construct perceptions drawing on our

experience and expectations Information not form our senses, knowledge based Interpretation

The Forest Has Eyes

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

Bottom-up is the colors, lines, angles of the horses, rider and sourroundings

Top-down is the title of the painting and what will give the painting meaning

Sensation and Perception Cycle

Thresholds

We live in a world on constant stimuliWhat do we notice and not notice?What do we feel and not feel?What do we sense and perceive?Psychophysics if the study of how physical

energy relates to our psychological experience What stimuli can we detect? At what intensity? How sensitive are we to changing stimulation

Psychophysics

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- Thresholds

Absolute Threshold What we are super-sensitive too, even if

the stimuli is faint Eyelash on our face is one example Absolute threshold is the minimum

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

Signal Detection Theory Signal Detection Theory

Detecting a weak stimuli depends on the signal’s strength but also on a psychological state

predicts how and when we detect a weak stimulus signal

Measured as ratio of “hits” to “false alarms” Why do people respond differently to same stimuli Why does same person’s reactions vary by

circumstances? Why parents hear the slightest sound fro their

baby, but miss louder sounds from other sources Detection depends partly on person’s

experience expectations motivation level of fatigue

Subliminal!

We have all heard of this Subliminal messages can be both visual and auditory Subliminal means stimuli below our threshold that we

unconsciously detect and perceive Remember that absolute threshold is 50% of the time

– so yes we can be and are stimulated by things below that threshold

Can we feel what we do not know and cannot describe?

Can we be manipulated using this? Psychologists say NO! When it appears that they do is it placebo effect?

Sensation- Thresholds

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

Sensation - Thresholds

Difference Threshold (aka JND – just noticeable difference) minimum difference between two stimuli

required for detection 50% of the time Increases with the magnitude of the stimulus

Weber’s Law- to be perceived as different, two stimuli must differ by a constant minimum percentage Stimuli must differ by a constant proportion

not amount to be noticed light intensity- 8% difference weight- 2% difference tone frequency- 0.3% difference

Sensory Adaptation

Diminished sensitivity as a consequence of constant stimulation

Example – you walk into a house and it smells, but an hour later you no longer notice the smell.

You get used to it – you adapt Diminishing sensitivity to

unchanging stimulus

End Day 1

Day 2 – Backmasking and Subliminal Clips and Discussion

Play several clips on subliminal messages and backmasking

Response: Students are to write a 2 paragraph response analyzing what they saw today (combined with Internet Research) and explain if subliminal and backmasking work.

Subliminal Commercials

End Day 2

Vision Amazing – how does light become images? Transduction

conversion of one form of energy to another Stimulus energy becomes neural messages

Stimulus input is light energy Not color that strikes the eyes, but electromagnetic

energy that our visual system perceives as color We se only a mall part of the color spectrum 2 parts of light help our sensory experience:

1. Wavelength - the distance from the peak of one wave to the peak of the next Determines hue (color we experience)

2. Intensity – Amount of energy in the light waves Influences brightness

Vision- Physical Properties of Waves

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)

The Eye Light enters the eye through the cornea

Light bends to provide focus

Light then passes through the pupil Pupil is an adjustable opening in the center of the

eye Pupil is regulated by the iris

Iris- a ring of muscle that forms the colored portion of the eye around the pupil and controls the size of the pupil opening

Adjusts light intake by dilating/constricting in response to intensity or even inner emotions

Behind the pupil is the lens

The Eye Continued

Lens focuses the incoming rays into an image on the eye’s light sensitive back surface

Does this through the process of accommodation – changing the curvature

Retina contains the receptor rods and cones and layers of neurons that process the visual information Rods – detect black, white and grey/peripheral and

twilight vision Cones – function in daylight and well-lit conditions/fine

detail/color sensations Fovea is the retina’s central area of focus add

where cones cluster around Fovea has cones but no rods

Vision

Vision

Acuity – sharpness of vision Can be changed by slight variations in the

shape of the eye Nearsightedness

Light rays from distant objects focus in the front of the retina

Condition in which nearby objects are seen more clearly than distant objects

Farsightedness The image of near objects is focused behind

retina Condition in which faraway objects are seen

more clearly than near objects

Vision

Normal Nearsighted Farsighted Vision Vision Vision

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

Vision- Receptors

Receptors 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

Pathways from the Eyes to the Visual Cortex

Day 4 – Vision in more detail

KQLW Chart Complete 1st 2 columns

What I already know/learned Questions I have still

Watch videos (also on website for class) G:\Eye\030 How Eyes Work - An Introduction.mp4

Start at 1:00 into the video G:\Eye\032 Visual Processing in the Retina.mp4

Start at 4:00 minutes into video Complete column 3

What I learned today KQLW Chart

Complete column 4 What I still want to learn

Start Day 5

Visual Information Processing

Visual information goes from the retina in the eye to the thalamus then to the brain’s visual cortex in the occipital lobe

130 million rods and cones in the retinaTransmitted by the ganglion cells

Ganglions’ axons make up the optic nerve

Retinal cells are VERY sensitive Can misfire Even pressure can trigger misfires Brain interprets the misfires as light

Feature Detection

Ganglion cells send signals to the visual cortex

Feature detector neurons respond to a scene’s specific features Edges, lines, angles and movements

Visual cortex passes information to other areas of the cortex that respond to more complex patterns

“Vast Visual Encyclopedia”

Cells that are distributed throughout the brain

Respond to one stimulus but not anotherCalled supercellsFire only when cues trigger them tooEx: A goalie blocking a shot when they

see the ball or puck coming or anticipate the direction it might come from

How the Brain Perceives

Perception combines sensory input with assumptions and expectations

If you stare at the Necker cube, it changes every few seconds This demonstrates

that perception is shifting

Brain constructs varying perceptions

Parallel Processing

Our brains process several things at onceDivides visual scene into dimensions

Color, depth, movement, and formOur perceptions are based on integration

of all from all the processing that happened simultaneously

Different areas of the brain process each part of the visual scene Damage one area and certain parts of vision

do not work i.e. pouring a drink into a class – appears

“frozen” – can’t see movement

Parallel Processing…

Summary of Processing of Visual Information

Color Vision

Light rays are NOT colored Color is in our brains – not

in the object we see The brain manufactures

color Theory is that any color can

be created by combining light waves of 3 colors Red, green, and blue Retina only has 3 color

receptors

Color-Deficient Vision

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

They have only 2 color receptors

Opponent-Process Theory

After leaving receptor cells, visual info is analyzed in terms of if the opponent colors

Neurons are turned on and off by certain colors“ON” “OFF”red greengreen red blue yellow yellow blue black whitewhite black

Opponent Process- Afterimage Effect

We get tired of our green response by staring at green

So – when we stare at the white (which contains all colors), we see only the red part of the red-green pairing

Color Constancy

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

In English – we see common objects as the same color even though the wavelengths may actually change.

End Day 5

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 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

Inner Ear innermost part of the ear, contining the

cochlea, semicurcular canals, and vestibular sacs

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

ear through which

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

Touch

Skin Sensations pressure

only skin sensation with identifiable receptors

warmth cold pain

Pain Gate-Control Theory

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

Taste Taste Sensations

sweet sour salty bitter

Sensory Interaction the principle that one sense may

influence another as when the smell of food influences its

taste

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 Movement

Kinesthesis the system for sensing the position

and movement of individual body parts

Vestibular Sense the sense of body movement and

position including the sense of balance