AP PsychologySensation and Perception

Alice F. ShortHilliard Davidson High School

Unit 3, Chapter 4

Sensation and Perception• sensation – the process of receiving stimulus energies

from the external environment and transforming those energies into neural energy– Relate to sensitive – 1.having the power of sensation, 2.

responsive to or aware of feelings, moods, reactions, etc., 3. easily irritated; delicate: sensitive skin, 4. affected by external conditions or stimuli

• perception – the process of organizing and interpreting sensory information so that it has meaning– Relate to perceptive - having or showing keenness of

insight, understanding, or intuition:

Sensation and Perception

• sensory receptors thalamus specific parts of the cerebral cortex

• sensation and perception = unified information-processing system

Bottom-up vs. Top-down Processing

• bottom-up processing – the operation in sensation and perception in which sensory receptors register information about the external environment and send it up to the brain for interpretation (part to whole)– song for first time

• top-down processing – the operation in sensation and perception, launched by cognitive processing at the brain’s higher levels, that allows the organisms to sense what is happening and to apply that framework to information from the world (whole to part)– favorite song

What do you see?

Predator vs. Prey

Categories of Sense Organs and Sensory Receptors

• sensory receptors – specialized cells that detect stimulus information and transmit it to sensory (afferent) nerves and the brain

3 main classes of sensory receptors:– photoreception – detection of light

• perceived as sight

– mechanoreception –detection of pressure vibration, and movement

• perceived as touch, hearing and equilibrium

– chemoreception – detection of chemical stimuli• perceived and smell and taste

Sensory Receptors

Name the category for each (photoreception, mechanoreception, or chemoreception)

Festive Disease for the Senses

• synaesthesia – an experience in which one sense (say, sight) induces an experience in another sense (say, hearing)– Possible Outcomes: see music, taste color – (seen in Criminal Minds, Season 8 “Magnificent

Light”)

Another Festive Disease for the Senses

• phantom limb pain –pain / felt movement of lost limb– Mirror therapy

Thalamus

• thalamus = relay station for brain (nearly all sensory information pass though the thalamus)– brain = complex (multiple pathways)

Absolute Sensory Thresholds

• The foolish definition of absolute threshold – the minimum amount of stimulus energy that person can detect (50 percent of the time)

Noise

• noise – term given to irrelevant and competing stimuli—not just sounds but any distracting stimuli for our senses

Difference Threshold (a.k.a. Just Noticeable Difference)

• difference threshold – the degree of difference that must exist between two stimuli before the difference is detected

• Weber’s law – the principle that two stimuli must differ by constant minimum percentage (rather than a constant amount) to be perceived as different– candle example (p. 103)

Subliminal Perception

• subliminal perception – the detection of information below the level of consciousness– Challenges the usefulness of the idea of

thresholds

– Read and discuss p. 103, Psychological Inquiry: “Subliminal Perception: Working Up a Thirst”

Signal Detection Theory

• signal detection theory –a theory of perception that focuses on decision making about stimuli in the presence of uncertainty– individual variations

• How are you feeling?

– contextual variations• What is the urgency of the situation?

Signal Detection Theory

• information acquisition – the information you can assess

• criterion – the basis for making a judgment from available information

Signal detection theory

Perceiving Visual Stimuli

• attention• perceptual set

Perceiving Sensory Stimuli: Attention

• attention – the process of focusing awareness on a narrowed aspect of the environment– selective attention – the process of focusing on a

specific aspect of experience while ignoring others– cocktail party effect (hearing specific voice)– Stroop effect – the way that automatically reading

a color name can make it difficult to name the color in which the word is printed

Stroop Effect• Stroop effect – the way that automatically reading a color name can make

it difficult to name the color in which the word is printed (p. 105)

• failure of selective attention

Attention• shiftable

– Monitoring many things at once• novel stimuli

– Novel– Different – Unusual

• size, color, movement• emotional stimuli (specific words, etc.)

– emotion-induced blindness – when we encounter an emotionally charged stimulus, we often fail to recognize a stimulus that is presented immediately after

• inattentional blindness – failure to detect unexpected events when our attention is engaged by tasks– counting basketball passes and gorilla costume (p. 106)

Perceiving Visual Stimuli: Perceptual Set

• perceptual set – a predisposition or readiness to perceive something in a particular way– children can be for accurate without solidified

perceptual sets

Sensory Adaption

• sensory adaption – a change in the responsiveness of the sensory stem based on the average level of surrounding stimulation– takes time– blind right after you turn off lights– freezing when first in pool

The Visual System

• The Visual Stimulus and the Eye• Visual Processing in the Brain• Color Vision• Perceiving Shape, Depth, Motion and

Constancy

Light

• Light – a form of electromagnetic energy that can be described in terms of wavelengths.– Travels though space in waves– Visible from 400 to 700 nanometers– Determines hue or color

• Wavelength – the distance from the peak of one wave to the peak of the next

• Amplitude – the height of the waves– determines the brightness of the stimulus

• Purity – whether all the waves are the same or different– Affects perceived saturation

The Structure of the Eye(p. 111-112)

• Sclera• Iris• Pupil • cornea• Lens• Curvature• Retina

• Rods• Cones• Fovea• Bipolar cells• Ganglion cells• Optic nerve• Blind spot

• Optic chiasm• Visual cortex

The Structure of the Eye (camera)(p. 111-112)

• sclera - the white, outer part of the eye that helps to maintain the shape of the eye and to protect it from injury

• iris – the colored part of the eye• pupil – the opening in the center of the iris; appears black• cornea – clear membrane just in front of the eye

– Bends light falling on the surface of the eye just enough to focus it at the back (brings image into focus)

• lens – a transparent and somewhat flexible disk-shaped structure filled with a gelatin-like material– Bends light falling on the surface of the eye just enough to focus it at

the back (brings image into focus)– Curvature – allows eye to focus on things up close (more curved) or

far away (flatter)• Ability to curve decreases with age (thus stylish reading glasses)

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&docid=uBcGJvkBuKf-lM&tbnid=3RQQzg7GpvNk7M:&ved=0CAUQjRw&url=http://www.eyesightresearch.org/background.htm&ei=IedbUrTrN83NkQfli4H4Dg&bvm=bv.53899372,d.eW0&psig=AFQjCNEEmznuxamNgOnZOAym0qY66V3nPQ&ust=1381841049001771

The Structure of the Eye (film)

• retina – the multilayered light-sensitive surface in the eye that records electromagnetic energy and converts it to neural impulses for processing in the brain (primary mechanism for sight)– rods – the receptor cells in the retina that are sensitive to light bun

not only very useful for color vision• Found almost everywhere on the retina except the fovea• Gives ability to detect fainter spots of light on the peripheral

– cones – the receptor cells in the retina that allow for color perception– fovea – a tiny area in the center of the retina at which vision is at its

best• contains only cones• explains difficulty of reading out of corner of eye

Structure of the Eye• (p. 112 of textbook)

Structure of the Eye: Retina

The Structure of the Eye

• retina bipolar cells ganglion cells (axons = optic nerve• bipolar cells – • ganglion cells – • optic nerve – the structure at the back of the eye, made

up of axons of the ganglion cells, that carries visual information for further processing

• blind spot – the place on the retina where the optic nerve leaves the eye on its way to the brain– cannot see anything that reaches only this part of the retina– brain uses top-down processing to to “fill in the gaps”

The Visual Processing in the Brain

• eyes = beginning of visual perception• brain = sent neural impulses for analysis and

integration• optic chiasm – point in brain where the optic

nerve fibers divide, and approximately half of the nerve fibers cross over the midline of the brain

Visual Processing

(p. 114)• visual information

originating in the right halves of the two retinas (from the left visual field) is transmitted to the right side of the occipital lobe in cerebral cortex; left half of retinas (right visual field) to left occipital lobe

The Visual Cortex

• visual cortex – most visual information is sent here before moving to other visual areas for further analysis – located in occipital lobe– is the part of cerebral cortex involved in vision

• feature detectors – neurons in the brain’s visual system that respond to particular features of a stimulus

The Visual Cortex: David Hubel and Torsten Wiesel (1963)

• won Nobel Prize for research on feature detectors (in cats)– recorded activity of a single neuron in a cat while it looked at

patterns that varied in size, shape, color , and movement– found that the visual cortex has neurons that are individually

sensitive to different types of lines and angles– Noted that when deprived of certain types of visual

stimulation early one, kittens lost the ability to perceive these patterns

• Suggests there might be a critical period in visual development and that the brain requires stimulation it its efforts to delegate its resources to different perceptual tasks brain “learns” to perceive through experience.

Perceiving Shape, Depth, Motion and Constancy

• contour – a location at which a sudden change of brightness occurs

• figure-ground relationship – the principle by which we organize the perceptual field into stimuli that stand out (figure) and those that are left over (ground)– Example: text (figure) on a page (ground)

Figure-Ground Relationship

Gestalt Principles

• gestalt psychology – a school of thought interested in how people naturally organize their perceptions according to certain patterns– main principle: the whole is different from the sum of its

parts -- computer screen image (sum) pixels (parts)– closure– proximity– similarity– continuity– law of Pragnanz

• “AP Psych – Gestalt Principles”

Gestalt Principles: Closure

• closure: disconnected or incomplete figures fill in the spaces and see them as complete figures

Gestalt Principles: Proximity

• proximity: object near each other see them as a unit (4 columns; not 16 squares)

Gestalt Principles: Similarity• similarity: objects that are similar seen as a

unit (columns of circles and squares; rows of circle and squares)

Depth Perception• depth perception – the ability to perceive objects

three-dimensionally (binocular and monocular cues)• binocular cues – depth cues that depend on the

combination of the images in the left and right eyes and on the way to the two eye work together– convergence - Binocular cue to depth and distance in

which the muscle movements in our two eyes provide information about how deep and/or far away something is

• up close eyes almost crossing

– disparity – difference between the images in the two eyes to determine the depth or distance of the object

• image “jumps” between eyes

Depth Perceptionp. 118

• monocular cues – powerful depth cues available from the image in one eye, either the right or the left– familiar size– height in the field of view– linear perspective and relative size– overlap– shading– texture gradient

• Read p. 118. Be prepared to apply terms to image on next slide.

© 2011 The McGraw-Hill Companies, Inc.

Monocular Cues: Shading, Texture Gradient

© 2011 The McGraw-Hill Companies, Inc.

Monocular Cues: Linear Perspective, Height in Field

Motion Perceptionp. 119

1. Neurons that are specialized to detect motion2. Feedback form our body tells us whether we

are moving or whether some one or some object is moving

3. The environment we see is rich with cues that give us information about movement

• apparent movement – the perception that a stationary object is moving

Perceptual Constancy

• perceptual constancy – the recognition that objects are constant and unchanging even though sensory input about them is changing (size, shape, color) demonstrates that we interpret sensation– size constancy– shape constancy (door example)– color constancy

© 2011 The McGraw-Hill Companies, Inc.

Visual Perception: Motion

Auditory System

• The Nature of Sound and How We Experience It• Structures and Functions of the Ear

– Outer ear– Middle ear– Inner ear

• Theories of Hearing• Auditory Processing in the Brain• Localizing Sound

The Nature of Sound and How We Experience It

• sound waves – vibration in the air that are processed by the auditory (hearing) system– frequency – the number of cycles (full wavelengths) that pass

through a point in a given time interval• pitch – the perceptual interpretation of the frequency of a sound

– complex sounds – sounds with numerous frequencies of sound blending together

• timbre – the tone saturation, or the perceptual quality, of a sound– Perceptual difference b/w different instruments playing the same note

– amplitude – the amount of pressure the sound wave produces relative to a standard, typically 0 decibels--measured in decibels (dB)

• loudness – the perception of the sound waves amplitude

Frequency • low frequency = low pitch• high frequency = high pitch• distinguish b/w adult and child

Amplitude

Decibels Source Exposure Danger

180 Space shuttle launch Hearing loss certain within 150 feet of launch pad

140 Jet aircraft motor Any exposure dangerous

120 Sandblaster, thunderclap Immediate danger

100 Heavy auto traffic, lawn mower

2 hours

60 Normal conversation No danger

40 Quiet office No danger

30 Quiet library No danger

20 Soft whisper No danger

0 Minimal detectable sound No danger

Volume

Complex Sounds: Timbre

• Timbre -

Structures and Functions of the Ear

• outer ear – the outermost part of the ear, consisting of the pinna and the external auditory canal

• middle ear – the part of the ear that channels sound through the eardrum, hammer, anvil, and stirrup to the inner ear

• inner ear – the part of the ear that includes the oval window, cochlea, and basilar membrane

© 2011 The McGraw-Hill Companies, Inc.

Structure of the Ear

Outer Ear

• pinna (plural, pinnae) – the outer, visible part of ear– collections sounds and channels them into the

interior of the ear– moveable in some animals (localization)

• external auditory canal

Middle Ear

• eardrum (tympanic membrane) – separates the outer ear from the middle ear– vibrates in response to sound

• hammer anvil stirrup – intricately connected chain of the three smallest bones in body– transmit sound waves to the fluid-filled inner ear (at

oval window) by vibrating– can amplify sounds or decrease intensity to protect

inner ear (muscles)

Inner Ear• inner ear – converts sound waves into neural

impulses to send to brain• oval window – transmits sound waves to the

cochlea (received from stirrup)• cochlea – tubular, fluid-filled structure, coiled

– basilar membrane – lines the inner wall of the cochlea and runs its entire length

• tells about frequency, pitch, complexity of sound• hair cells – ear’s sensory receptors (cilia sprout at top of hair

cells) – delicate damage can lead to deafness or difficulty hearing

– tectorial membrane – jellylike flap above hair cells• generates impulses that the brain interprets as sound

Cochlear Implant

• cochlear implant – a small electronic device that is surgically implanted in the ear and head– allows deaf or hard-of-hearing individuals to detect

sound– more effective the younger implanted

• DISUCSSION: Read Critical Controversy: “Are Cochlear Implants a “Cure for Deafness” (p. 124)– answer “What do you think?” questions– have thoughts

Theories of Hearing• place theory – theory on how the inner ear

registers the frequency of sound, stating that each frequency produces vibrations at a particular spot on the basilar membrane (better at explaining sounds below 1,000 firing per second)– high pitch tone – narrow area of basilar

membrane at the base of cochlear• explained well by theory

– low pitch tone – wide end of cochlea• explained poorly by theory

Theories of Hearing

• frequency theory – theory on how the inner ear registers he frequency of sound stating that the perception of a sound’s frequency depends on how often the auditory nerve fires– volley principle – modification of frequency theory

stating that a cluster of nerve cells can fire neural impulses in rapid succession, producing a volley of impulses

• combination of theories need for sounds above 1,000 times per second

Auditory Processing in the Brain

• auditory nerve – the nerve structure that receives information about sound from the hair cells of the inner ear and carries these neural impulses to the brain’s auditory areas (extends from the cochlea to brain stem)– left ear right side of brain– right ear left – side of brain– temporal lobe

Localizing Sound

• basilar membrane – tells about frequency, pitch, complexity of sound– NOTHING to do with location

• Localization:– sound shadow – caused by the listener’s head,

which forms a barrier that reduces the sound’s intensity

• timing• intensity

The Other Senses

• The Skin Senses– Touch– Temperature– Pain

• The Chemical Senses– Taste – Smell

• The Kinesthetic and Vestibular Senses

The Skin Senses

• skin – largest sensory system– cutaneous senses (3 types of receptors):

• touch (mechanical energy / pressure against skin)• temperature

– thermoreceptors – sensory nerve endings under the skin that respond to changes in temperature at or near the skin and provide input to keep the body’s temperature at 98.6 degrees Fahrenheit (heat = dominant)

• pain (adaptive for survival; intense stimulation of any sense produces pain)

– prostaglandin – stimulate receptors that cause the experience of pain (many painkiller reduce production)

– fast pathway thalamus (fast response required)– slow pathway detour in limbic system (tells you to “slow down”

your lifestyle – “nagging pain”)

Pain

• pain (adaptive for survival; intense stimulation of any sense produces pain)– prostaglandin – stimulate receptors that cause the

experience of pain (many painkiller reduce production)• fast pathway thalamus (fast response required)• slow pathway detour in limbic system (tells you to “slow

down” your lifestyle – “nagging pain”)

– endorphins – neurotransmitters (slow pathway)– factors: motivation, expectation, decision factors– women experience more pain

Chemical Senses• taste (sweet, sour, bitter, salty)

+ umami or yummy or savory (L-glutamate)– papillae – round bumps above the tongue's surface that

contain the taste buds, the receptors for taste (replaced every two weeks)

• 10,000 taste buds (younger)• 5,000 taste buds (older)

• smell– olfactory epithelium – the lining of the roof of the nasal

cavity, containing a sheet of receptor cells for smell• unique: neurons replace themselves after injury; don’t pass

through thalamus• temporal lobes various brain regions (including limbic system

– linked to emotion and memory (LOVE!)

– dogs – 100 times lower levels

The Kinesthetic and Vestibular Senses• kinesthetic (MOP) – movement, orientation, posture

– not in specific organ; embedded in muscle fibers and joints– same pathways to brain as touch

• vestibular (MB) – movement, balance (begins in auditory nerve, which contains both cochlear nerve and vestibular nerve for balance and movement)– connects to medulla (most), directly to cerebellum, temporal cortex, or

other places (not fully charted)– vision used in addition (when everything in visual field is moving…

generally WE are moving)– proprioceptive feedback – information about the position of our limbs

and body parts in relation to other body parts– semicircular canals of inner ear – three fluid-filled circular tubes that lie

in the three plans of the body• right-left• front-back• up-down

Sensation, Perception, and Health and Wellness

• Take care of yourself! You don’t regenerate.

THE END!