SENSATION AND PERCEPTION

SENSATION AND PERCEPTION
UNIT 4 SENSATION AND PERCEPTION

UNIT OVERVIEW Sensing the World: Some Basic Principles Vision Hearing
Other Senses Perceptual Organization Perceptual Interpretation Is there Extrasensory Perception?

SENSING THE WORLD: SOME BASIC PRINCIPLES

Perceptual Constancies
Sensation Vision The Eye Theories Hearing The Ear Other Senses Smell Taste Touch/Pain Gestalt Principles Perceptual Constancies Perception Basic Principles Visual Illusions Depth Perception We are here

SENSATION AND PERCEPTION
How do we construct our representations of the external world? To represent the world, we must detect physical energy (a stimulus) from the environment and convert it into neural signals. This is a process called sensation. When we give meaning by selecting, organizing, and interpreting our sensations, the process is called perception. OBJECTIVE 1| Contrast sensation and perception, and explain the difference between bottom-up and top-down processing.

INTRODUCTION Sensation Perception One continuous process…
receptors detect information Perception organization and interpretation of sensory information The process of creating meaningful patterns from raw sensory information One continuous process… *Sensation = Sensory receptors detect information *Perception = the organization and interpretation of sensory information that enables you to consciously recognize objects *In our everyday experiences, we blend sensation and perception into one continuous process.

WHAT DO YOU SEE vs WHAT DO YOU PERCEIVE?

INTRODUCTION Bottom-up processing Top-down processing
We start with sensory receptors and work up to higher levels of processing Sensory analysis that starts at the entry level = bottom-up processing We process this way when we have no prior knowledge. We start at the bottom and work our way up We construct perceptions on our experience & expectations = top-down processing We process this way when we have prior knowledge. We start at the top and have to work to process details. For example (picture of cowboy on horse with another horse): FORREST HAS EYES As our brain deciphers the information in the painting, bottom-up processing enables our sensory systems to detect the lines, angles and colors that form the horses, rider and surroundings. Using top-down processing we consider the painting’s title, notice the expressions, and then direct our attentions to aspects of the painting that will give those observations meaning (red arrows on slide) Without top=down processing, we would have to interpret the world as if it were constantly new. It would be like having to relearn how to add in math class every single day! Each organism in the world has different sensory gifts based on their needs: Frogs feed on flying insects; motionless insects = starving frog Our ears are sensitive to sound frequencies that include a human voice or a baby crying

BOTTOM-UP vs TOP-DOWN PROCESSING
Perception We start with sensory receptors and work up to higher levels of processing Sensory analysis that starts at the entry level = bottom-up processing We process this way when we have no prior knowledge. We start at the bottom and work our way up Sensation

CONSTRUCT A WHOLE FROM ITS PARTS
BOTTOM-UP PROCESSING Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind. We start with sensory receptors and work up to higher levels of processing Sensory analysis that starts at the entry level = bottom-up processing We process this way when we have no prior knowledge. We start at the bottom and work our way up Letter “A” is really a black blotch broken down into features by the brain that we perceive as an “A.” CONSTRUCT A WHOLE FROM ITS PARTS

CONCEPTUALLY DRIVEN, CONSTRUCTED ON EXPECTATIONS
TOP-DOWN PROCESSING Information processing is guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations. THE CHT We construct perceptions on our experience & expectations = top-down processing We process this way when we have prior knowledge. We start at the top and have to work to process details. For example (picture of cowboy on horse with another horse): FORREST HAS EYES As our brain deciphers the information in the painting, bottom-up processing enables our sensory systems to detect the lines, angles and colors that form the horses, rider and surroundings. Using top-down processing we consider the painting’s title, notice the expressions, and then direct our attentions to aspects of the painting that will give those observations meaning (red arrows on slide) Without top=down processing, we would have to interpret the world as if it were constantly new. It would be like having to relearn how to add in math class every single day! CONCEPTUALLY DRIVEN, CONSTRUCTED ON EXPECTATIONS

EXAMPLE OF TOP-DOWN PROCESSING
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SELECTIVE ATTENTION Selective attention Cocktail party effect
You are able to attend (hear) one voice among many; if you hear someone say your name, you will instantly bring their voice into consciousness Selective attention Through selective attention, your conscious awareness focuses, like a flashlight beam, on only a very limited aspect of all you experience. Our 5 senses take in 11,000,000 bits of information per second→ we consciously process 40 of them People with ADHD (attention deficit hyperactivity disorder) seem to lack the ability to be selectively attentive. Instead of filtering out unimportant stimuli in order to focus on important ones, they attend to all stimuli in the environment, making it difficult, if not impossible, to process information correctly Ex: Cocktail party effect (you are able to attend (hear) one voice among many; if you hear someone say your name, you will instantly bring their voice into your consciousness **Ask students to share their experiences where they were so caught up in an activity that they missed something so obvious in the environment, or when the environment was so distracting that they couldn’t concentrate

SELECTIVE ATTENTION SELECTIVE ATTENTION AND ACCIDENTS
Cell phone use and car accidents How was naturalistic observation used (Page 118) 80% of all traffic accidents are related to the driver being distracted Cell phone users are 4X more at risk when driving

SELECTIVE ATTENTION SELECTIVE ATTENTION AND ACCIDENTS
Inattentional blindness Video examples Videos: Gorilla Selective Inattention Inattentional blindness (failing to see visible objects when our attention is directed elsewhere EX: White, black shirts passing a basketball and ½ of people fail to notice the monkey suit walking in the middle of the circle, that the curtain changes from red to orange and one of the black shirted basketball players walks away

SELECTIVE ATTENTION SELECTIVE INATTENTION
Change blindness Change deafness Choice blindness Choice blindness – blindness Videos and DVD A form of inattentional blindness = change blindness (failing to notice a change in the environment) Experiment challenge—when people are so wrapped up in what they are supposed to be doing, they don’t notice that the experimenter changed people Choice blindness (known biases)—or choice blindness blindness (hidden biases are unknown)

POP – OUT PHENOMENON Some stimuli Pop-Out (ex: if you were to look at a picture of all sad faces, you would notice the one happy, smiling face because our eye demands our attention focus on that. Magicians exploit our change to blindness by selectively focusing our attention on the dramatic act with the inattention to change accomplished by their other hand.

THRESHOLDS Psychophysics
Psychophysics: the study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them.

ABSOLUTE THRESHOLD Smallest detectable LEVEL of a stimulus.
Gustav Fechner (German scientist & philosopher) studied faint stimuli and called them our absolute threshold Absolute threshold = the minimum stimulation necessary to detect a particular light, sound, pressure, taste or odor 50% of the time. (listening to pitches during a hearing test) Sensitivity to high-pitched sounds declines with normal aging (mosquito ring tones---younger generations can hear certain ring tones when older generations cannot)

DETECTION MUST BE 50% OF THE TIME
Absolute Threshold Intensity No No No Yes Yes Observer’s Response Detected Tell when you (the observer) detect the light.

ABSOLUTE THRESHOLDS Taste: 1 gram (.0356 ounce) of table salt in 500 liters (529 quarts) of water Smell: 1 drop of perfume diffused throughout a three-room apartment Touch: the wing of a bee falling on your cheek from a height of 1cm (.39 inch) Hearing: the tick of a watch from 6 meters (20 feet) in very quiet conditions Vision: a candle flame seen from 50km (30 miles) on a clear, dark night Measuring absolute thresholds: Vision: A single candle flame from 30 miles on a dark, clear night Hearing: The tick of a watch from 20 feet in total quiet Smell: 1 drop of perfume in a 6-room apartment Taste: 1 teaspoon sugar in 2 gallons of water Touch: The wing of a bee on your cheek, dropped from 1 cm Stimuli we detect less than 50% of the time = subliminal

THRESHOLDS SIGNAL DETECTION
Predicts how and when we detect the presence of a faint stimulus (signal) amid background noise (other stimulation). SDT assumes that there is no single absolute threshold and detection depends on: Signal detection theory: detecting a weak signal depends on the signal’s strength & psychological state Ex: Some teachers respond differently to misbehaving students People’s ability to catch a faint signal diminishes after about 30 minutes (depends on the task, time of day, if person exercises, experiences) Person’s experience Expectations Motivation Level of fatigue

THRESHOLDS SUBLIMINAL STIMULATION
Subliminal (below threshold) Priming Subliminal persuasion Subliminal Stimulation “Below the threshold” stimuli An invisible word can briefly prime (the activiation—often unconsciously—of certain associations, thus predisposing one’s perception, memory or response IF we are exposed to stimuli of a specific subject, we are more likely to recognize information about that subject in the environment Sometimes we feel what we do not know and cannot describe (smelling foul odors) Much of our information processing occurs automatically, out of sight, off the radar screen of our conscious mind If we did a brain scan, you would be able to detect brain activity with a faint, brief stimulus

THRESHOLDS DIFFERENCE THRESHOLDS
Just noticeable difference (jnd) Weber’s Law STIMULUS CONSTANT (k) Light 8% Weight 2% Tone 3% Difference Threshold Just noticeable difference (the minimum difference a person or animal can detect between any two stimuli half the time) Increases with the size of the stimulus Add 1 oz to a 10 oz weight = detectable difference vs. add 1 oz to a 100 oz weight = non-detectable difference EX: Musicians can detect minute discrepancies in an instrument’s tuning, students can detect their friends voices over all others in the hallway **Weber’s law: Ernest Weber—for a difference to be perceptible, two stimuli must differ by a constant proportion (not a constant amount) The exact portion varies, depending on the stimulus If a salesman wants to sell a 3 piece suit & a sweater to a customer—which do you try to sell first?? The suit because if a person pays $300 for a suit, they will not think much about a $75 sweater Same rule applies to accessories—people will pay more for accessories after they have made an expensive purchase. For the average person to perceive differences:

DIFFERENCE THRESHOLD The smallest detectable CHANGE in a stimulus
Also called the just noticeable difference (jnd)

DIFFERENCE THRESHOLD Difference Threshold: Minimum difference between two stimuli required for detection 50% of the time, also called just noticeable difference (JND). Difference Threshold No No Yes Observer’s Response Tell when you (observer) detect a difference in the light.

WEBER’S LAW Stimulus Constant (k) Light 8% Weight 2% Tone 3%
Two stimuli must differ by a constant minimum percentage (rather than a constant amount), to be perceived as different. Weber fraction: k = dI/I. Stimulus Constant (k) Light 8% Weight 2% Tone 3% Weber’s law: Ernest Weber—for a difference to be perceptible, two stimuli must differ by a constant proportion (not a constant amount) The exact portion varies, depending on the stimulus If a salesman wants to sell a 3 piece suit & a sweater to a customer—which do you try to sell first?? The suit because if a person pays $300 for a suit, they will not think much about a $75 sweater Same rule applies to accessories—people will pay more for accessories after they have made an expensive purchase. For the average person to perceive differences:

SENSORY THRESHOLDS Weber’s Law
States that the difference threshold is a constant proportion of the specific stimulus Senses vary in their sensitivity to changes in stimulation More than just sensation it has to do with sales. The exact portion varies, depending on the stimulus If a salesman wants to sell a 3 piece suit & a sweater to a customer—which do you try to sell first?? The suit because if a person pays $300 for a suit, they will not think much about a $75 sweater Same rule applies to accessories—people will pay more for accessories after they have made an expensive purchase. For the average person to perceive differences:

Who will notice if we add 2 lbs?
PUT IT ANOTHER WAY… Who will notice if we add 2 lbs?

SENSORY ADAPTATION Diminishing sensitivity to an unchanging stimulus
After constant exposure to a stimulus, our nerve cells fire less frequently Sensory Adaptation Our diminishing sensitivity to an unchanging stimulus (smell an odor when walking in to your neighbor’s home, but after a few moments, you don’t notice it any more) After constant exposure to a stimulus, our nerve cells fire less frequently Ex: What would your day be like if you concentrated on feeling different items you wear each day? Do you feel your socks gripping your ankles more, or your bracelet or watch tightening around your wrist? We focus more on changes in our environment instead of repetitive behaviors On TV = we pay more attention to cuts, zooms, pans and sudden noises than the same image over and over How do our senses work? Vision, Hearing, Smell, Taste, Touch

SENSORY ADAPTATION An adjustment of the senses to the level of stimulation they are receiving Ever forgotten you are wearing a watch? Ever gotten used to a smell? Then why don’t things disappear from your vision?

LIGHT Waves of electromagnetic energy Hits an object Some is absorbed
Some is reflected (the color you see) Human visible spectrum (roughly 400–700 nanometers wavelength) White Objects: Reflect all, absorb none. Black Objects: Absorb all, reflect none. So for example, an object appears "yellow" because the object removes "blue" from the wavelength that is incident upon the object.

TRANSDUCTION sensory info (e.g. sound waves, light waves, etc.) converted to a format the CNS can use… an ACTION POTENTIAL.

Sense Receptors Transduce…
TRANSDUCTION Unique transducers for each sense/organ Organ Sense Receptors Transduce… Eyes Light waves Ears Sound waves Tongue Flavor molecules Nose Scent molecules Skin Pressure energy Our eyes receive light energy and transduce (transform) it into neural messages that our brain then processes into what we consciously see (phototransduction).

ELECTROMAGNETIC ENERGY SPECTRUM
Our eyes receive light energy and transduce (transform) it into neural messages that our brain then processes into what we consciously see (phototransduction). What strikes our eye is pulses of electromagnetic energy that our visual system perceives as color (we only see a small slice of the electromagnetic spectrum Electromagnetic spectrum ranges from short gamma rays to the narrow band we see as visible light, to the long waves of radio transmission Bees cannot see red, but can see ultraviolent light, where we can see red, yellow, etc…. but not uv light

LIGHT Brightness: Hue:
Three physical characteristics of light help determine our sensory experience of them: Light’s wavelength (the distance from one wave peak to the next) determines its hue (the color we experience, such as blue or green) Wavelength determines the quality of the waves (for vision = color, for sound = pitch) Intensity (the amount of energy in light waves—determine by the wave’s amplitude or height) influences brightness Amplitude determines the intensity of the waves (for vision = brightness, for sound = loudness) Saturation (purity of the color)—the more pure the color, the more likely our eye will be to identify the color

THE PHYSICAL PROPERTY OF WAVES
Light’s wavelength (the distance from one wave peak to the next) determines its hue (the color we experience, such as blue or green) Wavelength determines the quality of the waves (for vision = color, for sound = pitch) Intensity (the amount of energy in light waves—determine by the wave’s amplitude or height) influences brightness Amplitude determines the intensity of the waves (for vision = brightness, for sound = loudness) Saturation (purity of the color)—the more pure the color, the more likely our eye will be to identify the color

THE EYE Cornea Pupil Iris Lens Retina Accommodation The Eye
Light enters the eye through the cornea (which protects the eye and bends light to provide focus) The light then passes through the pupil (a small adjustable opening surrounded by the iris—a colored muscle that adjusts light intake and controls the size of the pupil opening) The iris dilates or constricts in response to light intensity and even to inner emotions Red eye pictures? Usually red eye occurs in pictures where the surrounding illumination is dim, so the camera’s flash must be used to take an accurate picture. The flash is so quick, that the iris doesn’t have time to contract, making the pupil big enough to see right through to the red retina! Cameras with so-called “red eye reduction” features provide a series of quick flashes that warn the eye that a picture is about to be taken. The iris reacts to the light pulses and shrinks the pupil down so the retina is protected from the bright light. Behind the pupil is a lens that focuses incoming light rays into an image on the retina (a multilayered tissue on the eyeball’s sensitive inner surface—contains receptor rods and cones plus layers of neurons that begin the processing of visual information) The retina doesn’t “see” a whole image. Its millions of receptors cells convert particles of light energy into neural impulses and forward those to the brain. There the impulses are reassembled into a perceived, upright-seeming image The retina’s area of central focus = fovea The lens focuses the rays by changing its curvature (shape) in a process called accommodation (to focus near or far objects on the retina) Nearsightedness occurs when the lens focuses objects in front of the retina Farsightedness occurs when the lens focuses objects behind the retina

THE STRUCTURE OF THE EYE

Cornea: Covering. Bends light to focus it. Cornea = outer covering of the eye.

Pupil - black part of the eye Hole Fun fact about pupils: Contract when MORE LIGHT Dilate when LESS LIGHT, SEXUALLY AROUSED Pupil = the adjustable opening in the center of the eye through which light enters.

Iris – colored part of the eye Controls how much light enters the eye Iris = a ring of muscle tissue that forms the colored portion of the eye around the pupil and controls the size of the pupil opening. The iris dilates/constricts in response to changing light intensity

Lens: Where light goes after it enters pupil. Accommodation: Changes shape to focus light. Flat: Distant objects Fat: Near objects. Lens = the transparent structure behind the pupil that changes shape to help focus images on the retina.

Retina – membrane at back of eye – layers of tissue, contains rods and cones Rods – enable light/motion detection Cones – color vision Retina = the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information.

THE EYE: THE RETINA Rods and cones Rods Cones

RODS VERSUS CONES Rods: Enable light/motion detection
Share bipolar cells with other rods (send combined messages) Remain sensitive in dim light Cones: Cluster in and around the fovea Direct hotline to the brain – preserves precise information (better able to detect fine detail) Enable color vision only in bright light, in dim light color vision is lost Cones Cones cluster in and around the fovea Cones have their own hotline to the brain which devotes a large area to input from the fovea; this direct connections preserve the cones’ precise information, making them better able to detect fine detail Cones enable you to see color—only in bright light, in dim light you see no colors Rods No direct hotline; they share bipolar cells with other rods, sending combined messages You can detect something in your peripheral vision well before perceiving its details Enable black and white vision—remain sensitive in dim light

THE RETINA’S REACTION TO LIGHT
1. Light entering eye riggers photochemical reaction in Rods & cones (buried receptors cells) at the back of the retina 2. The light energy trigger chemical changes that would spark neural signals, activating neighboring bipolar cells. 3. The bipolar cells would activate the neighboring ganglion cells (the axons which converge to form the optic nerve—like the strands of a rope). The optic nerve then carries information to your brain (where the thalamus will receive and distribute the information) The optic nerve can send nearly 1 million messages at once through its nearly 1 million ganglion fibers *Where the optic nerve leaves the eye there are no receptor cells—creating a blind spot

GANGLION CELLS – CONNECT RETINA TO BRAIN

THE EYE: THE RETINA Optic nerve Blind spot fovea

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

Fovea – sharpness - V Fovea = the central focal point in the retina, around which the eye’s cones cluster.

Optic Nerve = the nerve that carries neural impulses from the eye to the brain.

VISUAL INFORMATION PROCESSING: VISUAL CORTEX

VISUAL INFORMATION PROCESSING: VISUAL CORTEX
The retina’s neural layers help to encode and analyze the sensory information Any given retinal area relays its information to a corresponding location in the visual cortex in the occipital lobe at the back of your brain, just above the cerebellum Your retinal cells are so responsive that even pressure triggers them if you close your eye and rub it; your brain interprets this pressure/firing as light

The Eye in a Nutshell Sclera: White
Iris: Colored. Controls size of pupil. Pupil: Black. Hole. Light enters, hits lens. Cornea: Covering. Bends light. Lens: Light hits here. Shifts shape to focus light. Retina: Membrane at back of eye. “Movie screen.” Where light becomes neural activity. Fovea: Sharpness. Contains cones. Color. Rods: Shapes Cones: Color Ganglion Cells: Connects retina to brain. Optic Nerve: Axons of ganglia, project to brain. Summing up, before we move onto Perception.

VISUAL PERCEPTION Our brain’s perceptual system compensates for missing information. Different parts of the cortex detect different components of vision (shape, edges, motion, color).

SHAPES: FEATURE DETECTION
Use minimal patterns to identify objects Ex: See edges of this object… identify it as a chair

FACE RECOGNITION An important aspect of social function!!
Brain areas responsible for recognizing faces: Temporal Lobes and Hippocampus

VISUAL INFORMATION PROCESSING: FEATURE DETECTION
Feature detectors Feature Detection Nobel Prize winners David Hubel and Torsten Wiesel (1979) demonstrated that neurons in the occipital lobe’s visual cortex receive information from individual ganglion cells in the retina. These feature detector cells derive their name from their ability to respond to scene specific features (edges, lines, angles & movements) Receptive fields, binocular interaction and functional architecture in the cat’s visual cortex—visual on slide Shape detectors in the visual cortex pass such information to other cortical areas where teams of supercell clusters respond to more complex patterns In the temporal lobe, it allows us to perceive faces Other lobes = chairs, houses

VISUAL INFORMATION PROCESSING: PARALLEL PROCESSING
Blind sight Parallel Processing Our brain engages in parallel processing (doing many things at once) The brain divides a visual scene into subdimensions (color, movement, form and depth) and works on each aspect simultaneously “Mrs. M” = A stroke damaged areas near the rear of both sides of her brain, she can no longer perceive movement People suddenly appear in a room Some people with a stroke or surgery damage to their brain’s visual cortex have experience blindsight: A localized area of blindness in a part of their field of vision Those with blindsight have superb vision, but they don’t know they can see. Their vision remains intact; only the neural areas that bring vision into awareness are impaired. Most people have a separate visual system for perception and action—dual processing brain Can’t identify objects, but can tell the detail of the object (vertical/horizontal, colors)

VISUAL INFORMATION PROCESSING

COLOR VISION Young-Helmholtz trichromatic (three color) theory
Red Green Blue Monochromatic Dichromatic Color Blindness Objects reflect long wavelengths of color (i.e. tomato = red) Our brain can discriminate 7 million different color variations 1 in 50 (usually males) have a color deficient (can’t distinguish between different colors) because the defect is genetically sex-linked Hermann von Helmholtz and Thomas Young developed the Young-Helmholtz trichromatic (three-color) theory: Any color can be created by combing the light waves of three primary colors (red, green ,blue) using three corresponding types of color receptors Our cones in our eyes do their color magic in teams of three; when we stimulate combinations of these cones, we see other colors EX: There are no receptors especially sensitive to yellow, but when both red-sensitive and green sensitive cones are stimulated, we see yellow.

COLOR VISION Opponent-process theory Three sets of colors Afterimage
Red / Green Yellow / Purple Blue / Orange Afterimage Most people who are color-deficient, are not actually “colorblind”; they lack functioning of the red or green sensitive cones (sometimes both) People who are colorblind se the color they are deficient in as a shade of muted gray or brown They may be monochromatic (one-color) or dichromatic (two-color) instead of trichromatic, making it impossible to distinguish the red & green 74 in the image on the slides Dogs lack receptors for the wavelengths of red, giving them only limited, dichromatic color vision Opponent-Process theory Ewald Hering discovered the occurrence of afterimages (British flag example As visual information leaves the receptor cells, we analyze it in terms of three sets of opponent colors: red-green, yellow-blue, and white-black **Color processing occurs in two stages: The retina’s red, green and blue cones respond in varying degrees to different color stimuli (Young-Helmholtz trichromatic theory) Their signals are then processed by the nervous system’s opponent process cells (en route to the visual cortex)

Opponent: Opposites Ex: When you stare at a red apple, you see a green afterimage. Opponent process theory - color vision is a function of complementary, opposing colors: red vs. green or blue vs. yellow For example, cells that are excited by red are inhibited by green, and vice versa

AFTERIMAGE

THE STIMULUS INPUT: SOUND WAVES
Audition Amplitude Loudness Frequency Pitch Hearing Our audition (hearing) is highly adaptive We hear best sounds with frequencies in a range corresponding of the human voice, sensitive to faint sounds (baby crying) We are attuned to variations in sounds (we recognize our friend’s voice over all the others in a busy hallway) Playing a violin (drawing the bow across it) results in stimulus energy = sound waves—jostling molecules of air—our ears detect brief air pressure changes

THE STIMULUS INPUT: SOUND WAVES
Amplitude loudness Frequency pitch We hear by both air and bone conduction Then our ears transform the vibrating air into nerve impulses, which our brain decodes as sound **The strength (amplitude) of sound wave determines its loudness Waves vary in length (frequency) The frequency determines the pitch we experience (long waves = low frequency = low pitch) (short waves = high frequency = high pitch) **We measure sounds in decibels Absolute threshold for hearing = 0 decibels

THE EAR Outer ear Auditory canal Ear drum The Ear
How does the ear transform sounds waves/energy into neural messages our brain interprets?

THE STRUCTURE OF THE EAR
The ear is divided into the outer, middle and inner ear.

1. The visible outer ear channels the sound waves through the auditory canal to the eardrum (a tight membrane that vibrates with the waves) The sound waves travel down the auditory canal to the eardrum.

Eardrum = tight membrane that vibrates when struck by sound waves.

Eardrum

THE EAR Middle ear Hammer, anvil, stirrup

2. The middle ear then transmits the ear drum’s vibrations through a piston made of three tiny bones (hammer, anvil and stirrup) to the cochlea (a snail-shaped tube in the inner ear). Bones of the middle ear = the hammer, anvil, stirrup which vibrate with the eardrum.

Hammer

Anvil

Stirrup

3. The incoming vibrations cause the cochlea’s membrane (the oval window) to vibrate, jostling the fluid that fills the tube. Oval window = where the stirrup connects to the cochlea.

4. This motion causes ripples in the basilar membrane, bending the hair cells lining its surface A cochlea has 16,000 hair cells Cochlea = a coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses.

THE EAR Inner ear Cochlea Auditory nerve Auditory cortex Oval window
Basilar membrane Auditory nerve Auditory cortex

Oval Window

Cochlea

Fluid in the cochlea

**Damage to hair cells accounts for most hearing loss If you are exposed to sounds louder than 85 decibels for a prolonged period of time; it can result in hearing loss (if you hear ringing in your ears = hearing’s equivalent to bleeding) Men’s hearing tends to be less acute than women’s because they are more likely to blast loud music for long periods of time **Earplugs or walk away! Hair cells in the cochlea

5. Hair cell movement triggers impulse in the adjacent nerve cells, whose axons converge to form the auditory nerve, which sends neural messages (via the thalamus) to the temporal lobe’s auditory cortex. Auditory nerve = nerve which sends the auditory message to the brain via the thalamus.

Nerve fibers

Auditory nerve

NEURAL IMPULSE TO THE BRAIN

THE EAR: PERCEIVING LOUDNESS
Basilar membrane's hair cell Compressed sound Perceiving Loudness The brain can interpret loudness from the number of activated hair cells For those with hearing loss, they differ in our sensation of soft sounds Hard of hearing people usually do not want all sounds amplified---they can typically hear loud sounds, just not soft sounds They like sounds compressed—harder-to-hear sounds are amplified more than loud sounds—a feature with newer hearing aids

COCHLEA AND LOUD SOUNDS

Place Theory and Frequency Theory
PITCH THEORIES Place Theory and Frequency Theory

THE EAR: PERCEIVING PITCH
Place theory High pitched sounds Hear different pitches that trigger activity at different places along basilar membrane Frequency theory Low pitched sounds Brain reads pitch by monitoring frequency of neural impulses Volley principle – neurons alternate firing Perceiving Pitch Herman von Helmholtz’s place theory = we hear different pitches because different sound waves trigger activity at different places along the cochlea’s basilar membrane The brain determines a sound’s pitch by recognizing the specific place (on the membrane) that is generating the neural signal Different frequencies of sound waves are said to vibrate different places on the cochlea. These places are wired to different parts of the auditory cortex in the brain so the sound can be processed correctly **Best explains how we sense high pitches The frequency theory suggests that the brain reads pitch by monitoring the frequency of neural impulses traveling up the auditory nerve. The whole basilar membrane vibrates with the incoming sound wave, triggering neural impulses to the brain at the same rate as the sound wave (if a the sound wave has 100 frequency waves per second; then 100 pulses per second travel up the auditory nerve) The entire cochlea is believed to vibrate at a particular frequency, thus sending the signal of the quality of the sound to the brain **Best explains how we sense low pitches

THE EAR: LOCATING SOUNDS
Stereophonic hearing Localization of sounds Intensity Speed of sound Locating Sounds Two ears are better than one If a car to the right honks , your right ear receives a more intense sound , and it receives sounds lightly sooner than your left ear Sound travels 750 miles per hour Hard to distinguish the intensity difference being sent between our ears (6 inches apart) But if you were trying to distinguish a sound ahead, behind, above or below you, you would make some mistakes (finger snapping experiment with a student sitting down, eyes closed)

Nerve (sensorineural) Deafness
Conduction Deafness Nerve (sensorineural) Deafness Something goes wrong with the sound and the vibration on the way to the cochlea. You can replace the bones or get a hearing aid to help. The hair cells in the cochlea get damaged. Loud noises can cause this type of deafness. NO WAY to replace the hairs. Cochlea implant is possible. Conduction hearing loss: Problems with the mechanical system that conducts sound waves to the cochlea If the eardrum is punctured or if the tiny bones of the middle ear lose their ability to vibrate, the ear’s ability to conduct vibrations diminishes. Sensorineural hearing loss: Damage to the cochlea’s hair cell receptors or their associated nerves can cause this (nerve deafness) Can be linked to disease, biological changes with heredity, aging, prolonged exposure to ear-splitting noise or music The only way to restore hearing for people with nerve deafness = bionic ear = cochlear implant (translates sounds into electrical signals that –wired to the cochlea’s nerves—convey some information about sound to the brain 60,000 people in the world have cochlear implants (2003); millions more are potential candidates 500 million people in the world live with hearing loss

COCHLEAR IMPLANTS Cochlear implants are electronic devices that enable the brain to hear sounds. OBJECTIVE 16| Describe how cochlear implants function, and explain why Deaf culture advocates object to these devices. Where these implants are pertinent for hearing parents with deaf children, deaf culture advocate not using them especially on children deafened before learning to speak. The only way to restore hearing for people with nerve deafness = bionic ear = cochlear implant (translates sounds into electrical signals that –wired to the cochlea’s nerves—convey some information about sound to the brain 60,000 people in the world have cochlear implants (2003); millions more are potential candidates 500 million people in the world live with hearing loss Cochlear Implant

OTHER SENSES

TOUCH Skin is the largest sense organ
There are receptors for pressure, temperature, and pain Touch appears to be important not just as a source of information, but as a way to bond with others Touch Localization Touch localization depends on the relative lengths of the pathways from the stimulated parts to the brain.

TOUCH Types of touch Hairy/Glabrous skin Pressure Warmth Cold Pain
Sensation of hot Hairy/Glabrous skin Touch From birth, touch is essential to our development; animals and infants who are not stimulated by touch, develop poor self-esteem and are usually unhappy Our “sense of touch” or skin is a mix of distinct senses with different specialized nerve endings within the skin Some are sensitive to pressure, warmth, cold, pain Only pressure has identifiable receptors Stimulating nearby cold and warms spots produces the sensation of hot Two types of skin: Hairy skin (contains hair cells, which detect movement and pressure) Glabrous skin (contains no hair cells, so the receptors in this type of skin are more sensitive. Found on the palms of hands, bottoms of feet, lips)

TOUCH Rubber hand illusion

TOUCH Kinesthesis: sense of position and movement of body
Vestibular sense: monitors head/body position and movement Semicircular canal: fluid within moves when head rotates/tilts Important sensors in your joints, tendons, bones and ears and skin sensors enable your kinesthesis (your sense of the position and movement of your body parts) Vision interacts with kinesthesis People who lose their kinesthetic sense = proprioception lose the ability to move unless they can see themselves move. When they see their bodies, their brains are able to process what needs to be done to move. In the dark, these people become limp and collapse to the floor. Our vestibular sense monitors your head’s/body’s position and movement Our inner ear and fluid within our semicircular canals & vestibular sacs moves when your head rotates or tilts This movement stimulates hair-like receptors, which send messages to the cerebellum at the back of the brain, thus enabling you to sense your body position and to maintain your balance After you spin around & get dizzy, the dizzy aftereffect fools your brain to think you are still spinning—neither your semicircular canals nor your kinesthetic receptors will immediately return to their neutral state

VESTIBULAR SACS Vestibular Sacs

SEMICIRCULAR CANALS

PAIN: UNDERSTANDING PAIN
Biological pain Nociceptors (sensory receptors that detect hurtful stimuli) Endorphins Phantom limb sensations Pain Pain is your body’s way of telling you something is wrong Some people are born (genetically) without the ability to feel pain→ can experience severe injury or die if not monitored Pain is mainly governed by nerves known as “free nerve endings”, which are not directly connected to any specific nervous system Pain seems to be regulated within its own system, working where needed to signal the body to a painful stimulus. Pain experiences can vary widely (depending on our physiology, our experiences and attention and culture) No one type of stimulus which triggers pain There are different nociceptors--- sensory receptors that detect hurtful temperatures, pressures or chemicals Psychologist Ronald Melzack and biologist Patrick Wall: Gate-control theory-the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain. The “gate” is opened by the activity of pain signals traveling up small nerve fibers and is closed by activity in large fibers or by information coming from the brain. Helps to explain why people aren’t always aware of pain. Pain signals can be controlled by the brain. The brain can sometimes choose which pain to consider and which to ignore, blocking off pain signals in the spinal cord that it chooses to ignore. Rubbing the area around your stubbed toe will create competing stimulation that will block some pain signals When we are distracted from pain & soothed by the release of endorphins our experience of pain may be greatly diminished

GATE CONTROL THEORY Spinal cord contains small nerve fibers that conduct most pain signals It also contains larger fibers that conduct most other sensory signals When tissue is injured small nerve fibers activate and open the neural gate BUT… Large fiber activity shuts that gate Thus if you stimulate gate closing activity by massage electrical signal or acupuncture you can disrupt the pain message. The brain can close this gate too! Psychologist Ronald Melzack and biologist Patrick Wall: Gate-control theory-the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain. The “gate” is opened by the activity of pain signals traveling up small nerve fibers and is closed by activity in large fibers or by information coming from the brain. Helps to explain why people aren’t always aware of pain. Pain signals can be controlled by the brain. The brain can sometimes choose which pain to consider and which to ignore, blocking off pain signals in the spinal cord that it chooses to ignore. Rubbing the area around your stubbed toe will create competing stimulation that will block some pain signals When we are distracted from pain & soothed by the release of endorphins our experience of pain may be greatly diminished

Ashley Blocker (right) feels neither pain
Pain tells the body that something has gone wrong. Usually pain results from damage to the skin and other tissues. A rare disease (CIPA) exists in which the afflicted person feels no pain. OBJECTIVE 18| State the purpose of pain, and describe the biopsychosocial perspective on pain. Pain Pain is your body’s way of telling you something is wrong Some people are born (genetically) without the ability to feel pain→ can experience severe injury or die if not monitored Pain is mainly governed by nerves known as “free nerve endings”, which are not directly connected to any specific nervous system Pain seems to be regulated within its own system, working where needed to signal the body to a painful stimulus. Pain experiences can vary widely (depending on our physiology, our experiences and attention and culture) No one type of stimulus which triggers pain There are different nociceptors--- sensory receptors that detect hurtful temperatures, pressures or chemicals AP Photo/ Stephen Morton Ashley Blocker (right) feels neither pain nor extreme hot or cold.

THE PAIN CIRCUIT

Psychological influences Rubber-hand illusion (mirror neurons) Memories of pain Psychological influences: We edit our memories of pain (which often differ from the pain we actually experienced) We record pain at the peak moment, register pain at the end

Social-cultural influences Socio-cultural influences: We tend to perceive more pain when others also seem to be experiencing pain Our experience of pain is much more than neural messages sent to the brain

BIOPSYCHOSOCIAL APPROACH TO PAIN

PAIN: CONTROLLING PAIN
Physical methods Psychological methods Can be treated both physically and psychologically: Drugs, surgery, acupuncture, electrical stimulation, massage, exercise, hypnosis, relaxation training and thought distraction (thinking pleasant thoughts or counting backwards by 3s)→ diverting one’s attention from pain can be helpful in alleviating its effects Given a placebo can help to dampen the pain feeling (think you are receiving a pain medication) Image explanation: For burn victims undergoing painful skin repair, an escape into virtual reality can powerfully distract attention, thus reducing pain and the brain’s response to painful stimulation. The MRI scans illustrate a lowered pain response when the patient is distracted.

TASTE Four basic tastes Sweet Salty Sour Bitter

UMAMI Recent discovery of fifth taste
Umami – Japanese word meaning pleasant savory taste. People taste umami through receptors for glutamate, commonly found in its salt form as the food additive monosodium glutamate (MSG)

TASTE Taste buds Chemical sense Age and taste
Little bumps on top and sides of tongue Taste receptor cells inside taste bud pores Chemical sense Age and taste As we age, number and sensitivity of taste buds decreases Tastes sensations = sweet, sour, salty, bitter, --added recently umami (meaty taste—flavor enhancer) Survival functions: Sweet indicates energy source Salty indicates sodium essential to physiological processes Sour indicates potentially toxic acid Bitter indicates potential poisons Umami indicates proteins to grow and repair tissue Taste is a chemical sense 200+ taste buds (little bumps on the top & sides of your tongue) each contain a pore that catches food chemicals Into each taste bud pore = taste receptor cells which project antennalike hairs that sense food molecules Taste receptors reproduce every week or two (so when you burn your tongue on a hot pizza, it hardly matters As you grow older, the number of taste buds & your sensitivity decreases

TASTE FOR SURVIVAL

TASTE: SENSORY INTERACTION
Interaction of smell and taste McGurk Effect Interaction of other senses Sensory Interaction The principle that one sense may influence another, as when the smell of food influences its taste When you have a cold (stuffed up nose), food is not as enjoyable to eat Smell + texture + taste = flavor Seeing, hearing, smelling, touching, tasting are blended by our brain when inputting into our system

SMELL Like taste, smell is a chemical sense. Odorants enter the nasal cavity to stimulate 5 million receptors to sense smell. OBJECTIVE 20| Describe the sense of smell and explain why specific odors so easily trigger memories.

SMELL Olfaction Chemical sense Odor molecules Olfactory bulb
Olfactory nerve SMELL We inhale/exhale 20,000 breaths of life-sustaining air—the results of experiencing smell = olfaction Smell is a chemical sense We smell something when molecules of a substance reach a tiny cluster of 5 million + olfactory receptor cells at the top of each nasal cavity and respond selectively They alert the brain through their axon fibers (olfactory neurons bypass the brain’s sensory switchboard (thalamus) Smell is processed near the prefrontal cortex before it is sent along We can identify & detect 10,000 odors molecules and identify patterns of past odor molecules to identify fresh fruit vs. rotten fruit Smell is the most primitive sense and most difficult to describe & recall Some animals have many times more olfactory receptor cells than humans do and use their sense of smell to communicate and navigate We have a remarkable capacity to recognize long-forgotten odors and their associated memories (ex: smell of the sea, the scent of a perfume)

SMELL (OLFACTION) We smell something when molecules of a substance reach a tiny cluster of 5 million + olfactory receptor cells at the top of each nasal cavity and respond selectively They alert the brain through their axon fibers (olfactory neurons bypass the brain’s sensory switchboard (thalamus) Smell is processed near the prefrontal cortex before it is sent along We can identify & detect 10,000 odors molecules and identify patterns of past odor molecules to identify fresh fruit vs. rotten fruit Smell is the most primitive sense and most difficult to describe & recall Some animals have many times more olfactory receptor cells than humans do and use their sense of smell to communicate and navigate We have a remarkable capacity to recognize long-forgotten odors and their associated memories (ex: smell of the sea, the scent of a perfume)

AGE, GENDER AND SMELL Ability to identify smell peaks during early adulthood, but steadily declines after that. Women are better at detecting odors than men.

SMELL AND MEMORIES The brain region for smell (in red) is hard wired into brain regions involved with memory (limbic system – amygdala and the hippocampus). That is why strong memories are made through the sense of smell. Smell is the most primitive sense and most difficult to describe & recall We have a remarkable capacity to recognize long-forgotten odors and their associated memories (ex: smell of the sea, the scent of a perfume)

SYNESTHESIA The extraordinary sensory condition in which stimulation of one modality leads to perceptual experience in another. Literally, the term means “to perceive together.” typographic synesthesia

PERCEPTUAL ORGANIZATION

OUR BRAINS ARE MEANING MACHINES
We organize the sensory information coming into our brains. We make assumptions about the sensory information. Oftentimes our perception is greater than the sum of the parts actually presented to our senses.

GESTALT PSYCHOLOGY From the German word meaning ‘the whole’
Studied human perceptual self-organizing tendencies. Found that the brain creates a coherent perceptual experience that is more than simply the sum of the available sensory information AND it does this in predictable ways So predictable that artists can exploit our common perceptions to do things like 3D art OBJECTIVE 3| Describe Gestalt psychology's contribution to our understanding of perception. A group of German psychologists noticed that when given a cluster of sensations, people tend to organize them into a gestalt (German word for “form” or “whole”)→ EX: Necker cube (see different circles, a white cube, all meet together to form a cube shape)

SIDEWALK CHALK ART

FIRST STEP IN VISUAL PERCEPTION
Determine Figure from the background (figure-ground) We organize the visual field into objects (figures) that stand out from their surroundings (ground).

FORM PERCEPTION: FIGURE AND GROUND
What you make the figure and what you make the background determines your perception Our first perceptual task is to perceive any object (the figure) as distinct from its surroundings (the ground) The figure-ground relationship of an object continuously reverses—we always organize the stimulus into a figure seen against the ground

Mother, Father and daughter!!!
And finally………. The WHOLE family! Mother, Father and daughter!!! Our first perceptual task is to perceive any object (the figure) as distinct from its surroundings (the ground) The figure-ground relationship of an object continuously reverses—we always organize the stimulus into a figure seen against the ground

Our first perceptual task is to perceive any object (the figure) as distinct from its surroundings (the ground) The figure-ground relationship of an object continuously reverses—we always organize the stimulus into a figure seen against the ground

Can you find nine people in this picture?
Our first perceptual task is to perceive any object (the figure) as distinct from its surroundings (the ground) The figure-ground relationship of an object continuously reverses—we always organize the stimulus into a figure seen against the ground

FORM PERCEPTION: GROUPING
Proximity Similarity Continuity Connectedness Closure Form Perception Grouping: The perceptual tendency to organize stimuli into coherent groups based on color, movement, light/dark contrast—more specifically: Proximity: We group nearby figures together Similarity: We group similar figures together Continuity: We perceive smooth, continuous patterns Connectedness: Because patterns are uniform and linked, we perceive them as a single unit Closure: WE fill in gaps to create a complete, whole object Some principles usually help us to construct reality, sometimes however lead us astray (doghouse or optical illusions video clip)

FORM PERCEPTION: GROUPING
Proximity Closure Similarity Continuity Connectedness

FORM PERCEPTION: GROUPING-PROXIMITY
Proximity: we group nearby figures together Proximity: We group nearby figures together

FORM PERCEPTION: GROUPING-CLOSURE
Closure: We fill in gaps to create a complete, whole object Closure: We fill in gaps to create a complete, whole object

PROXIMITY AND CLOSURE

FORM PERCEPTION: GROUPING-SIMILARITY
Similarity: we group similar figures together Similarity: We group similar figures together

FORM PERCEPTION: GROUPING-CONTINUITY
Continuity: we perceive smooth, continuous patterns Continuity: We perceive smooth, continuous patterns

FORM PERCEPTION: GROUPING-CONNECTEDNESS
Connectedness: we perceive patterns as a single unit because they are uniform and linked Connectedness: Because patterns are uniform and linked, we perceive them as a single unit

FORM PERCEPTION: GROUPING-CONNECTEDNESS
Connectedness: Because patterns are uniform and linked, we perceive them as a single unit The Principle of Common Region states that objects that are within the same region are perceptually grouped together.

DEPTH PERCEPTION Depth perception enables us to judge distances. Gibson and Walk (1960) suggested that human infants (crawling age) have depth perception. Even newborn animals show depth perception. OBJECTIVE 5| Explain the importance of depth perception, and discuss the contribution of visual cliff research to our understanding of this ability. Depth Perception Depth Perception: Seeing objects in three dimensions-enables us to estimate their distance from us Seeing an oncoming car approaching Eleanor Gibson & Richard Walk placed 6-14 month infant on the edge of a safe canyon (visual cliff). When the infant mother’s tried to coax them to cross over the glass towards them, most were reluctant because they came prepared to perceive depth Even newborns and young animals can perceive depth and grows with age and experience (more they crawl, the more aware they are) Visual Cliff

DEPTH PERCEPTION: BINOCULAR CLUES
Binocular cues Depth perception that we have because we have TWO eyes Binocular Cues Depth cues (retinal disparity) to judge the distance of nearby objects using two eyes When the brain compares two slightly different images from our eyes, the difference between them is retinal disparity—provides a binocular cue for perceiving depth The greater the difference between the two images, the closer the object The creators of 3D movies simulate or exaggerate retinal disparity The old-fashioned Viewmasters—cover one eye and look through the view finder—then look with both Finger Sausage trial: Try looking at your two index fingers when pointing them towards each other half an inch apart and about 5 inches directly in front of your eyes. You will see a “finger sausage” as shown in the inset.

RETINAL DISPARITY Retinal disparity: Images from the two eyes differ.
While focusing far away try touching your fingers about 5 inches directly in front of your eyes. You will see a “finger sausage” The amount of disparity (difference) between the two images can be used as a cue for distance Try holding up two fingers one in front of the other. Focus on the front one (you should now see two images of the back one). Now move the back one away from, then back towards you, while still focusing on the front one.

BINOCULAR CUES: CONVERGENCE
Convergence: Neuromuscular cues. When two eyes move inward (towards the nose) to see near objects and outward (away from the nose) to see faraway objects. OBJECTIVE 6| Describe two binocular cues for perceiving depth, and explain how they help the brain to compute distance.

DEPTH PERCEPTION: MONOCULAR CUES
Horizontal-vertical illusion Monocular Cues Horizontal-vertical illusion: our perceiving vertical dimensions as longer than identical horizontal dimensions (St. Louis Gateway Arch—looks taller, but it is as wide as it is tall)

DEPTH PERCEPTION: MONOCULAR CUES
Relative height Relative size Interposition Linear perspective Relative motion Light and shadow Monocular Cues Depth cues, such as interposition and linear perspective, available to either eye alone

DEPTH PERCEPTION: MONOCULAR CUES – RELATIVE HEIGHT
Relative Height: We perceive objects higher in our field of vision as farther away Relative height: We perceive objects higher in our field of vision as farther away. Because we perceive the lower part of a figure-ground illustration as closer, we perceive it as figure. Invert the illustration above and the black becomes ground, like a night sky.

DEPTH PERCEPTION: MONOCULAR CUES – RELATIVE SIZE
Relative Size: If two objects are similar in size, we perceive the one that casts a smaller retinal image to be farther away. Relative size: If we assume two objects are similar in size, most people perceive the one that casts the smaller retinal image as farther away

DEPTH PERCEPTION: MONOCULAR CUES – INTERPOSITION
Interposition: Objects that occlude (block) other objects tend to be perceived as closer. Interposition: If one object partially blocks our view of another, we perceive it as closer. The depth cues provided by interposition make this an impossible scene.

DEPTH PERCEPTION: MONOCULAR CUES – LINEAR PERSPECTIVE
Linear Perspective: Parallel lines, such as railroad tracks, appear to converge in the distance. The more the lines converge, the greater their perceived distance. Linear Perspective: Parallel lines, such as railroad tracks, appear to converge with distance. The more they converge, the greater their perceived distance.

DEPTH PERCEPTION: MONOCULAR CUES – RELATIVE MOTION
Relative motion: Objects closer to a fixation point move faster and in opposing direction to those objects that are farther away from a fixation point, moving slower and in the same direction. Relative motion: As we move, objects that are actually stable may appear to move. If while riding on a bus you fix your gaze on some object—say, a house—the objects beyond the fixation point appear to move with you; objects in front of the fixation point appear to move backward. The farther those objects are from the fixation point, the faster they seem to move.

DEPTH PERCEPTION: MONOCULAR CUES – LIGHT AND SHADOW
Light and Shadow: Nearby objects reflect more light into our eyes than more distant objects. Given two identical objects, the ones that are shaded on top are seen as “sticking out toward us” Light and Shadow: Nearby objects reflect more light to our eyes. Thus, given two identical objects, the dimmer one seems farther away. Shading, too, produces a sense of depth consistent with our assumptions that light comes from above. Invert the illustration on the slide, and the hollow in the bottom row will become a hill.

MOTION PERCEPTION Phi phenomenon: Stroboscopic motion:
Created by a rapid series of still pictures Phi phenomenon: Apparent motion created by lights flashing in sequence Max Wertheimer (founder of Gestalt psychology) observed the phi phenomenon (where individual flashing lights could be made to look like they were chasing each other by putting them in a time sequence. He noticed that by looking at each light individually, you lost the whole effect of the lights chasing each other. He felt that studying individual behaviors took away from appreciating the whole person) We constantly filter sensory information and infer perceptions in ways that make sense to us. If you could not see motion, you would not be able to walk, write, eat, bike or drive To catch a fly ball, you run with the ball that’s flying your way Phi phenomenon: When two adjacent stationary light blink on and off in quick succession—we perceive a single light moving back and forth between them (moving arrow on a sign) **Our brain constructs our perception

PERCEPTUAL CONSTANCY Perceptual constancy – ability to recognize objects without being deceived by changes in their shape, size, brightness or color even as illumination and retinal images change Perceptual Constancy The ability to recognize objects without being deceived by changes in their shape, size, brightness, or color even as illumination and retinal images change Top-down process which lets us identify people and things in less time than it takes to draw a breath Sometimes an object whose actual shape cannot change seems to change with the angle of our view

PERCEPTUAL CONSTANCY: SHAPE AND SIZE CONSTANCY
Shape Constancy: we perceive the form of familiar objects as remaining the same even if projected retinal image changes Sometimes an object whose actual shape cannot change seems to change with the angle of our view Shape constancy: we perceive the form of familiar objects (door shape)

PERCEPTUAL CONSTANCY: SHAPE AND SIZE CONSTANCY
Size constancy: we perceive objects as having a constant size, even if projected image appears to change sizes Sometimes an object whose actual shape cannot change seems to change with the angle of our view Size constancy: we perceive objects as having a constant size (a car is large enough to carry people even though it looks very small from 2 blocks away) There is a close connection between perceived distance and perceived size Perceiving an object’s distance gives us cues to its size Ponzo Illusion: The distant monster and the top red bar appear bigger because of distance cues. Experience tells us that a more distant object can create the same-size image as a nearer one only if it is actually larger---the illusion makes the object that is farther away look larger, when in reality it is not Moon illusion: The moon looks up to 50% larger when on the horizon compared to when it is high in the sky Ponzo illusion Moon illusion

AMES ROOM Adelbert Ames’ room: Even though one girl looks taller than the other, the room is distorted (the girls are actually the same height)

AMES ROOM https://www.youtube.com/watch?v=gJhyu6nlGt8
**Demo: Have students hold a hand in front of them at arm’s length and move it toward their head, then away; they will perceive no change in size. Now have students hold the pointer finger of their left hand about 8 inches in front of their face and focus on it. They should then position their right hand at arm’s length, past their left pointer finger. While maintaining fixation on their left fingertip, they should move their right hand toward and away from their face. Although their focus should be on the finger, they should also notice the image of the hand as it moves. It will change dramatically in size. Brain Games (season 2) – “Seeing is Believing” – 6:09

PERCEPTUAL CONSTANCY: LIGHTNESS CONSTANCY
Lightness/brightness constancy: we perceive an object as having a constant lightness even when its illumination varies Relative luminance: amount of light an object reflects is relative to its surroundings Lightness Constancy White paper reflects 90% of the light falling on it; black paper only 10% Brightness constancy/lightness constancy: we perceive an object as having a constant lightness even while its illumination varies Perceived lightness depends on relative luminance (see image on slide)—the amount of light an object reflects is relative to its surroundings Example: If you are up early in the morning and it’s still dark out, it is hard to find the matching black vs. blue sock. If you turn the light on or wait for sunrise—it is easier to distinguish

PERCEPTUAL CONSTANCY: COLOR CONSTANCY
Color constancy: we perceive familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object Surrounding context Surrounding objects Color Constancy Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object: A red apple in a bowl by itself retains its redness; by keeping in mind the surrounding context, when seeing the apple with other fruits, its color will remain roughly constant as the lighting and wavelengths shift *Color depends on context in its surrounding objects Importance of Perceptual constancy: our brain has the power to make sense out of nonsense!

PERCEPTUAL INTERPRETATION
We are born with the ability to tell the difference between figure and ground and can sense colors (Immanuel Kant— ) Experience guides and sustains the brain’s development as it forms pathways that affect our perceptions (John Locke – ) Eyes and mouth play a dominant role in face recognition. Madonna picture: Portrait artists understood the importance of this recognition and therefore centered an eye in their paintings.

SENSORY DEPRIVATION AND RESTORED VISION
Experiments on sensory deprivation Critical period Sensory deprivation Kittens raised without exposure to horizontal lines later had difficulty perceiving horizontal bars.

PERCEPTUAL ADAPTATION
Displacement goggles Perceptual adaptation Given a new pair of glasses or new contact lenses, we may feel a little strange, even dizzy. Within a day or two, we adjust Perceptual adaptation: In vision, the ability to adjust to an artificially displaced or even inverted visual field If you are given goggles which turns the world upside, you are able to adapt to the context and learned to coordinate your movements

PERCEPTUAL SET Perceptual set: a bias or readiness to perceive certain aspects of available sensory data and to ignore others Perceptual Set Our experiences, assumptions, and expectations may give us a perceptual set/mental predisposition that greatly influences (top-down) what we perceive. Image example: Show a friend either the left (saxophone player) or right image (woman’s face). Then show the center image and ask “What do you see?” Whether your friend reports seeing a saxophone or a woman’s face will likely depend on which of the other two drawings was viewed first. In each of those images, the meaning if clear, and it will establish perceptual expectations. Once we have formed a wrong idea about reality, we have more difficulty seeing the truth. Loch Ness monster or a log? …………Flying saucers or clouds? Much of what we perceive comes from our experiences and what we see/hear Through experience, we form schemas: that organize and interpret unfamiliar information We recognize people by facial features that cartoonists can caricature

SCHEMAS Schemas: used to organize and interpret unfamiliar information
Once we have formed a wrong idea about reality, we have more difficulty seeing the truth. Loch Ness monster or a log? …………Flying saucers or clouds? Much of what we perceive comes from our experiences and what we see/hear Through experience, we form schemas: that organize and interpret unfamiliar information We recognize people by facial features that cartoonists can caricature

PERCEPTUAL SET: CONTEXT EFFECTS
“eel” on the wagon vs “eel” on the orange morning vs mourning Context Effects Our brain can work backward in time to allow a later stimulus to determine how we perceive an earlier one “eel is on a wagon” = wheel is on a wagon… Context can radically impact our perception---is the “magician’s cabinet” on the floor or hanging from the ceiling? In each case, the context of the rabbits guides our perception Stereotypes and schemas can define perception of gender Studying, reading or watching TV should not occur while lying in bed. People who do this associate studying with sleeping since they study where they sleep

Cultural Context Culture influences perception. Most Westerners (North/South Americans) have no trouble interpreting the image of people sitting inside of a dwelling. They do not confuse the window with a box on the woman’s head. However those from other cultures that do not share the same perceptual sets perceive the scene differently (said the woman was balancing a metal box or can on her head and that the family was sitting under a tree)

PERCEPTUAL SET: EMOTION AND MOTIVATION
Motivation on perception Emotion on perception **Perception is also influenced by our emotions and motivation If a person is tired, walking a long trek will be overwhelming If a person receives a reward to perceive a particular drawing, they will identify that drawing **The river of perception is fed by sensation, cognition and emotion→ need multiple levels of analysis (Biopsychosocial approach)

PERCEPTION IS A BIOPSYCHOSOCIAL PHENOMENON

IS THERE EXTRASENSORY PERCEPTION?

CLAIMS OF ESP Parapsychology Extrasensory perception
Clairvoyance – awareness of an unknown object or event Telepathy – knowledge of someone else’s thoughts or feelings Precognition – foreknowledge of future events Psychokinesis –movement of physical objects by the mind without the use of physical means Extrasensory Perception ESP: The controversial claim that perception can occur apart from sensory input; includes telepathy, clairvoyance (the ability to perceive things beyond an ordinary means of perception) and precognition

PARAPSYCHOLOGY the study of paranormal phenomena
Parapsychology: the study of paranormal phenomena (ESP & psychkinesis—movement of physical objects by the mind without the use of physical means—levitating a table, influencing the roll of dice)

PARAPSYCHOLOGY the study of paranormal phenomena

PREMONITIONS OR PRETENTIONS?
Psychic predictions Nostradamus Parapsychology: the study of paranormal phenomena (ESP & psychkinesis—movement of physical objects by the mind without the use of physical means—levitating a table, influencing the roll of dice) 96% of scientists are skeptical that such phenomena exist For 26 years, virtually never have psychics anticipated any of the year’s headlines, predicted the outcome of a lottery jackpot, or make billions on the stock market Many have had stunning coincidences—but not predictions, just chance Correlation does not mean causation (just because events occur together, does not mean that they can cause each other)

PUTTING ESP TO THE EXPERIMENTAL TEST
ESP experiments Claims of paranormal phenomena (“psi”); Astrological predictions, psychic healing, communication with the dead, out-of-body experiences Most testable/relevant: Telepathy (mind-to-mind communication) Clairvoyance (perceiving remote events—sensing that a friend’s house is on fire) Precognition (perceiving future events—sporting event’s outcome) **Confirmation bias: occurs when we only look for evidence that supports our beliefs and ignore evidence that refutes them. Many people believe in parapsychology because they rely only on the evidence that supports their beliefs. James Randi’s debunking psychics video from earlier in the semester→ encourages psychics to test their beliefs to see if they work

SENSATION AND PERCEPTION

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