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SENSATION AND PERCEPTION
Sensation: your window to the world
Perception: interpreting what comes in your window.
http://study.com/academy/lesson/intro-to-sensation-and-perception.html
AP EXAM Sensation and Perception (6–8%)
AP students in psychology should be able to do the following: • Discuss basic principles of sensory transduction, including absolute threshold,
difference threshold, signal detection, and sensory adaptation. • Describe sensory processes (e.g., hearing, vision, touch, taste, smell, vestibular,
kinesthesis, pain), including the specific nature of energy transduction, relevant anatomical structures, and specialized pathways in the brain for each of the senses.
• Explain common sensory disorders (e.g., visual and hearing impairments). • Describe general principles of organizing and integrating sensation to promote
stable awareness of the external world (e.g., Gestalt principles, depth perception).
• Discuss how experience and culture can influence perceptual processes (e.g.,perceptual set, context effects).
• Explain the role of top-down processing in producing vulnerability to illusion. • Discuss the role of attention in behavior. • Challenge common beliefs in parapsychological phenomena. • Identify the major historical figures in sensation and perception (e.g., Gustav
Fechner,
David Hubel, Ernst Weber, Torsten Wiesel).
VIDEO
Brain Games https://www.youtube.com/watch?v=4mSxiWypQ
OA
THE BASICS
We do not actually experience the world directly, but instead we experience it through a series of “filters” we call senses.
The brain senses the world indirectly because the sense organs convert stimulation into the language of the nervous system: neural messages
The study of these sense and their effect on our behavior is called sensory psychology.
SENSATION Sensation: The process by which our stimulated
sensory receptors (eyes, ears…) and nervous system receive stimulus from the environment.
OUR SENSES You will notice that all of our sense organs are
very much alike. They all transform physical stimulation (such as
light waves or sound waves) into the neural impulses what give us sensations (such as light and dark).
PERCEPTION
Perception: The process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.
Perception creates an interpretation of sensation.
Do you see faces or vases?
SENSATION AND PERCEPTION
Perception is essentially an interpretation and elaboration of sensation. Therefore, sensation refers to the initial steps in the processing of a stimulus.
These pictures should look similar
The True Picture
THE FAMOUS MONA LISA…FROWN OR SMILE
THE FAMOUS MONA LISA…FROWN OR SMILE
WHAT IF WE COULD SENSE EVERYTHING?
Life would hurt.
So we can only take in a window of what is out there.
This is the study of psychophysics: relationship between physical stimuli and our psychological experiences to them.
TRANSDUCTION: CHANGING STIMULUS TO SENSATION
In all the sense organs, it is the job of sensory receptors to convert incoming stimuli information into electrochemical signals—neural activity.
Transduction: The sensory process that converts energy, such as light or sound waves, into the form of neural messages.
Transduction with Hearing
TRANSDUCTION Information goes from
the senses to the thalamus , then to the various areas in the brain.
Remember the movie Sky High? The student in orange changes his body to slime. Solid form to liquid form. Change from one form of energy to another. Click the picture to watch the video of power placement.
A SIMPLE EXAMPLE
Close both of your eyes. Press gently in the corner of one eye. You should “see” a pattern caused by pressure of your finger, not by light.
These light sensations are phosphenes, or visual images caused by fooling your visual system into thinking it sees light.
SENSORY ADAPTATION
Sensation is critically influenced by change. Thus, our sense organs are change detectors.
Their receptors specialize in gathering information about new and changing events.
SENSORY ADAPTATION Sensory adaptation - diminishing responsiveness
of our sensory systems to prolonged stimulation.
Unless it is quite intense or painful, stimulation that persists without change in intensity usually shifts to the background of our awareness.
Until now, many of you are probably unaware that your sense of touch had adapted to the pressure of the chair against your legs.
Do you feel your underwear all day?
THE CONCEPT OF SENSORY ADAPTATION APPLIES TO ALL OF OUR SENSES.
ABSOLUTE THRESHOLDThe minimum stimulation needed to detect a stimulus 50% of the time.
DO YOU HEAR ANYTHING?
HOW OLD ARE YOUR EARS?
DIFFERENCE THRESHOLD The minimum difference that a person can
detect between two stimuli. Also known as Just Noticeable Difference
DIFFERENCE THRESHOLD (JUST NOTABLE/NOTICEABLE DIFFERENCE)
The smallest amount of change needed to detect a change in a stimulus
WEBER’S LAW Ernst Weber noted that for people to really perceive a
difference, the stimuli must differ by a constant "proportion" not a constant "amount".
WEBER’S LAW EXAMPLEIf you are buying a new computer that costs $1,000 and you want to add more memory that increases the and the price $200 (a 20% increase), you might consider this too much additional money to spend.
However, if you were buying a $300,000 house a $200 feature may seem like nothing. It might take an additional $10,000 to make you stop and think if it's too much to spend.
In this example, the amount stays the same ($200), but the proportion changes and that's what makes the perceptual difference.
LAWS OF SENSATION
Fechner’s Law: The size of JND is proportional to the intensity of the stimulus; the JND is large when the intensity of the stimulus is high.
Steven’s Power Law: A law of magnitude that is more accurate than Fechner’s law and covers a wider variety of stimuli.
SIGNAL DETECTION THEORY
Predicts how we detect a stimulus amid other stimuli.
Assumes that we do not have an absolute threshold.
We detect stuff based on our experiences, motivations and fatigue level.
SUBLIMINAL STIMULATION Below one’s absolute threshold for
conscious awareness.
Does this work?Yes and No
• Slide studies showed some emotional reactivity (called priming a response).
• The effects are subtle and fleeting.
DO SUBLIMINAL MESSAGES WORK?
Based on studies, some people do respond to stimuli below the absolute threshold, under some circumstances. The problem is people
behave different thresholds at different levels, so what could be subliminal (or below the threshold) for one person, may be supraliminal (above the threshold) for another person.
0
25
50
75
100
LowAbsolutethreshold
Medium
Intensity of stimulus
Percentageof correctdetections
Subliminal stimuli
LET’S LOOK AT A FEW SUBLIMINAL CLIPS
Wendy’s http://www.youtube.com/watch?v=7hpucDMiZmc
Frozen https://www.youtube.com/watch?v=WLS5jbSWcAk
Disney https://www.youtube.com/watch?v=5QaYdph-aNM
Our most dominating sense Vision is the most complex,
best developed and most important sense for humans and other highly mobile creatures. Think of the eye as the
brain’s camera. It gathers light, focuses it,
converts it to a neural signal and sends these signals on for further processing.
http://study.com/academy/lesson/how-does-vision-work.html
VISION
PHASE ONE: GETTING THE LIGHT IN THE EYERODS AND CONESFOVEA
HOW THE EYE WORKS The eye transduces the characteristics of light
into neural signals that the brain can process.
Transduction happens in the retina, the light sensitive layer of cells at the back of the eye.
PARTS OF THE EYE
Cornea – light enters Pupil – adjustable
opening through which light enters
Iris – ring of muscle that forms color part of eye and controls the size of pupil
Lens – focuses incoming light rays into an image on the retina
Retina – light sensitive inner surface of the eye Rods Cones Neurons that begin
processing visual information
How the Eye Works
PHOTORECEPTORS
Photoreceptors: Light-sensitive cells (neurons) in the retina that convert light energy into neural energy.
Rods: Photoreceptors that are especially sensitive to dim light, but not color. (125 mil/eye)
Cones: Photoreceptors that are especially sensitive to colors but not dim light. (7 mil/eye) Cones are responsible for our ability to “see” colors.
THE FOVEA The fovea is the area of
sharpest vision.
It has the highest concentration of rods and cones.
THE OPTIC NERVE AND THE BLIND SPOT
Optic Nerve: The bundle of neurons that carries the visual information from the retina to the brain. This is where the stimulus, once changed into a
neural impulse, gets passed onto the brain. (transduction into the brain)
Blind Spot: The point where the optic nerve exits the eye and where there are no photoreceptors. Any stimulus that falls on this area cannot
be seen.
FEATURE DETECTORS
We have specific cells that see the lines, motion, curves and other features of this turkey. These cells are called feature detectors.
PARALLEL PROCESSING
In the visual cortex, the brain begins working by transforming neural impulses into visual sensations of color, form, depth and movement.
• This process is called parallel processing-the simultaneous processing of several aspects of a problem
THEORIES OF HOW WE SEE COLOR?
OPPONENT-PROCESS THEORY
The sensory receptors come in pairs.
Red/Green Yellow/Blue Black/White If one color is
stimulated, the other is inhibited.
AFTER IMAGES
Stare at the eye of the red parrot while you slowly count to 20, then immediately look at one spot in the empty birdcage. The faint, ghostly image of a blue-green bird should appear in the cage.
EXPLANATION OF GHOSTLY AFTER IMAGES The ghostly birds are called afterimages.
As you stare at the red bird, light-sensitive cells at the back of your eyes become less responsive to red light. This is called the opponent processing theory.
Opponent Processing Theory: there are some color combinations that we never see, such as reddish-green or yellowish-blue.
Color perception is controlled by the activity of two opponent systems; a blue-yellow mechanism and a red-green mechanism
When you shift your gaze to the birdcage, your visual system “subtracts” red light from the white light that’s being reflected from the white background. White light minus red light is blue-green light.
AFTERIMAGES
OPPONENT PROCESS- AFTERIMAGE EFFECT
TRICHROMATIC THEORY(YOUNG-HELMHOLTZ THEORY)
Three types of cones:• Red• Blue• Green
These three types of cones can make millions of combinations of colors.
Does not explain afterimages or color blindness well.
Most colorblind people simply lack cone receptor cells for one or more of these primary colors.
WE ONLY USE LIGHT ENERGY TO SEE.
AP Test Tip:Humans only see a small %
of the wavelengths
of light.
WAVELENGTH
The distance from the peak of one light wave to the peak of the next.
• The distance determines the hue (color) of the light we perceive.
INTENSITY
The amount of energy in a light wave.
Determined by the height of the wave.
The higher the wave the more intense the light is.
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)
COLOR VISION
A COLORLESS WORLD
Despite the way the world appears, color does not exist outside the brain, because color is a perception that the brain creates based on the wavelength of light striking our eyes.
Color is created when the wavelength in a beam of light is recorded by the photoreceptors in the form of neural impulses.
It is then sent to specific regions of the brain for processing.
COLOR BLINDNESS Color blindness can be classified as inherited,
partial or complete.
Inherited color blindness is most common in males, affecting both eyes but does not worsen over time - in other words, once you have it, you have it.
Partial color blindness affects some colors while
complete color blindness, which is a rare condition, affects all your color vision.
More common is color weakness, where people have a hard time distinguishing between certain colors.
VARIOUS TYPES OF COLOR BLINDNESS
COLOR BLIND TEST
Disclaimer: Information provided on this website is intended for your general information only and must not be regarded as a replacement for professional health advice. If you have, or suspect you have a health problem, please consult your doctor.
HEARINGCRASH COURSE
Our auditory sense
HEARING
The vibrational energy of vibrating objects, such as guitar strings, transfer the surrounding medium-air-as the vibrating objects push the molecules of the medium back and forth.
In space, there is no air, so the sound wave would have no medium to push. Any explosion would be eerily without sound.
FREQUENCY AND AMPLITUDE There are two physical characteristics of sound:
frequency and amplitude.
Frequency: The number of cycles of complete wavelengths in a given amount of time-determines pitch of a sound.
Amplitude: How loud the sound is. The higher the crest of the wave, the louder the sound. It is measured in decibels. The maximum extent of a vibration or displacement of a
wave, measured from the position of equilibrium.
AMPLITUDEPITCH
THE PROCESS OF HEARING The middle ear transmits the
vibrations (sound waves) hit the eardrum anvil hammer stirrup cochlea’s membrane (oval window)
The incoming vibrations cause the cochlea’s membrane (oval window) the to vibrate, moving the fluid that fills the tube. This motion causes ripples in the basilar membrane (hair cells).
The movement of cells triggers impulses in the adjacent nerve fibers which form the auditory nerve that connects via the thalamus to the temporal lobe.
It is all about the vibrations!
THE EARKHANACADEMY. PT1PT 2
PLACE THEORY
Different hairs vibrate in the cochlea when they hear/ interpret different pitches.
So some hairs vibrate when they hear high pitches and other vibrate when they hear low pitches.
FREQUENCY THEORY
The rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch.
All the hairs vibrate but at different speeds.
HOW WE LOCATE SOUNDS
Let’s do a simple experiment!
IF A TREE FALLS IN THE FOREST…
The question “If a tree falls in the forest and there is no one around to hear it, does it still make a sound?” can now be answered.
No, it would make no sound.
Sound is a purely psychological sensation that requires an ear (and the rest of the auditory system) to produce it.
DEAFNESSKHANACADEMY.COCHLEAR IMPLANT
Conduction Deafness
Something goes wrong with the mechanical/vibration process in hearing.
Hearing aids to help.
Nerve (Sensorineural) Deafness
The hair cells in the cochlea get damaged.
Loud noises can cause this type of deafness.
NO WAY to replace the hairs. Cochlear implant is possible.
POSITION AND MOVEMENT
There are two physical mechanisms that keep track of body position.
Vestibular sense: Tells us where our body is oriented in space.
Our sense of balance.
The receptors for this information are tiny hairs in the semicircular canal of the inner ear.
Vestibular System
POSITION AND MOVEMENT
The kinesthetic sense keeps track of body parts, relative to each other. Kinesthesis provides
constant sensory feedback about what the muscles in your body are doing.
Receptors for kinesthesis reside in joints, muscles and tendons. These receptors are usually automatic, unless the person is learning a new skill.
Smell and Taste
WHY DO WE STUDY SMELL AND TASTE TOGETHER?
SENSORY INTERACTION: the principle that one sense may influence another.
TASTE The sense of taste is gustation.
Human taste has four main qualities: sweet, sour, bitter and salty.
Specialized nerves carry nothing but the taste messages to the brain.
Taste is realized on a specialized region of the parietal lobe’s somatosensory cortex.
HOW DO WE TASTE?• Taste (and smell) are chemical senses.
What is the central muscle involved in taste?
PAPILLAE
Those bumps on our tongue are called Papillae.
Papillae help grip food while your teeth are chewing. They also have another special job - they contain your taste buds
TASTE
Taste receptors can be easily damaged by alcohol, smoke, acids or hot foods.
Fortunately, gustatory receptors are frequently replaced.
SMELL The sense of smell is olfaction.
Odors first interact with receptor proteins associated with hairs in the nose.
The hairs convey information to the brains olfactory bulbs, located on the underside of the brain.
In humans, olfaction has a close connection with memory.
Certain smells, such as a favorite perfume, can evoke emotion-laden memories.
GENDER RELATED ODORS Can you smell the difference between?
Hands, Breath, Shirts
SO CAN WE SMELL THE DIFFERENCE?
Well….yes and no.
Pheromones• Chemical messengers that are picked up through
our sense of smell.
• Founded in the early 1930’s by studying silkworms.
• Jury is still out on whether they exist in humans.
THE PHREMONE THEORY
TOUCH Receptors located in our skin.
Gate Control Theory of Pain- the spinal cord contains a neurological "gate" that either blocks pain signals or allows them to continue on to the brain.
Pain is sensed by two different sensory pathways, one moving very fast, one moving slower.
The level of pain one feels results from the combination of information from both pathways Video.
GATE-CONTROL THEORY Ultimately, pain signals are routed to the anterior
cingulate cortex located along the fissure separating the frontal lobes. Pain medication works by blocking the faster of the
two neural pathways.
Vision – Seeing – VisualAudition – Hearing – Auditory
Olfaction – Smelling – Olfactory
Gustation – Tasting – Gustatory
WE DO NOT PERCEIVE THE
WORLD HOW IT REALLY IS, BUT AS IT
IS USEFUL FOR US TO PERCEIVE IT.
PERCEPTION
The process of organizing and interpreting information, enabling us to recognize meaningful objects and events.
Perception brings meaning to sensation. It produces an interpretation of the world, but it isn’t a perfect representation.
The images are exactly the same except for the thick black area in the right image (an example of the Poggendorff illusion (1860)). In the figure on the right, there appear to be two continuous diagonal lines: a red and a blue line. What occurs in your visual system that could account for the appearance of the continuous diagonal lines?
DESCRIBE THIS PICTURE
• Bottom-Up: Lines, angles and colors…a guy riding a horse through the forest
• Top-Down: We consider the title and direct our attention to aspects that will give meaning to it.
The Forest Has Eyes by Bev Doolittle
BOTTOM-UP AND TOP-DOWN
Bottom-Up processing: Analysis that emphasizes the characteristics of the stimuli rather than our concepts and expectations.
Top-Down perception: Analysis that emphasizes the perceiver’s expectations, concept memories and other cognitive factors, rather than individual characteristics.
ILLUSIONS
Sometimes your mind will play a trick on you and interprets a stimulus incorrectly.
When your mind interprets an image that is demonstrably incorrect, it is called an illusion.
Lets look at an illusion!
PERCEPTUAL CONSISTENCY The ability to recognize the same object as
remaining “constant” under changing conditions is called perceptual consistency.
There are three examples of perceptual consistency including size (different distances), color (different lighting) and shape (different angles).
TYPES OF BLINDNESS
In-attentional Blindness: Failing to see visible objects when our attention is directed elsewhere. Moon-walking Bearhttps://www.youtube.com/watch?v=Qghh2Zsh3CY
Change Blindness: Failing to notice change in the environment around us. Card Trick https://www.youtube.com/watch?v=FWSxSQsspiQ
Choice Blindness: Failing to notice a change in a previously selected item Face Test http://channel.nationalgeographic.com/channel/brain-games/video
s/choice-blindness/
THE HERMANN GRID
Stare at the center of grid. Note how dark fuzzy spots appear at the intersections of the white bars.
Now focus on the intersections, there are no spots.
Why does this illusion exist?
While most cones have a direct neural pathway to the brain, rods do not and have to share with many other neurons. Not all can send their information at the same time, so we are left with mini “blind spots.”
HOW THE ILLUSION WORKS
The reason for this illusion lies in the way the receptor cells in your visual pathway interact with each other.
The firing of certain cells that are sensitive to light-dark boundaries inhibits other cells that would detect the white lines. This blocking process makes you sense darker regions.
THE GESTALT THEORY Gestalt Psychologists argue that the brain
forms a perceptual whole that is more than the mere sum of its sensory parts.
PRE-WIRED
Humans see a square as a single figure rather than four lines.
Psychologists argue that examples like this show that humans organize sensory information into meaningful patters. The most basic of these patterns are pre-wired into our brains at birth.
FIGURE AND GROUND Gestalt Psychology divides perceptual experience
into figure and ground.
Figure: The part of a pattern that commands attention…stands out.
Ground: The part of the pattern that does not command attention…background.
CLOSURE: FILLING IN THE BLANKS
Our minds do a funny thing, they provide closure. That is, they make us see incomplete images as wholes by supplying the missing segments or filling in gaps.
Generally, humans have a natural tendency to perceive stimuli as complete and balanced even when the pieces are missing.
What shapes do you see in each image?
PERCEPTUAL SET Perceptual set is a readiness to detect a
particular stimulus in a given situation—think of when you are afraid and staying home alone and you notice every noise and think it is a threat.
Here is another example. What is the last word in each line?
FOX; OWL; SNAKE; TURKEY; SWAN; D?CK
BOB; RAY; DAVE; BILL; TOM; D?CK
PERCEPTUAL SET A mental predisposition to perceive one
thing and not another. Based on schemas; why?
LAW OF PERCEPTUAL GROUPING
Law of Similarity: The Gestalt principle that we tend to group similar objects together in our perceptions.
Do you see x o x o xrows or x o x o xcolumns? x o x o x
x o x o xx o x o x
LAW OF PERCEPTUAL GROUPING
Law of Proximity: The Gestalt principle that we tend to group objects together when they are near each other.
Do you see 5 Xs and 5 Os, or 5 pairs of Xs and Os?
XO XO XO XO XO
LAW OF PERCEPTUAL GROUPING
Law of Common Fate: The Gestalt principle that we tend to group similar objects together that share a common motion or destination.
Think a school of fish, a flock of seagulls, a murder of crows
LAWS OF PERCEPTUAL GROUPING Law of Pragnanz: The Gestalt principle which
states that the simplest organization, requiring the least cognitive effort, will emerge as the figure. Your mind wants to make the most meaningful yet
easiest interpretation of stimuli that it can make
What is wrong with this image?
SELECTIVE ATTENTION
The focusing of conscious awareness on a particular stimulus.
COCKTAIL-PARTY PHENOMENON
The cocktail party effect describes the ability to focus one's listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversations.
Form of selective attention.
DEPTH PERCEPTION The ability to see objects in three dimensions
although the images that strike the retina are two dimensional.
Allows us to judge distance.
HOW DO WE TRANSFORM TWO-DIMENSIONAL OBJECTS TO THREE-DIMENSIONAL PERCEPTION?
Binocular Cues: depth cues that depend on two eyes
Monocular Cues: depth cues that depend on one eye
BINOCULAR CUES
Retinal Disparity: a binocular cue for seeing depth.
The closer an object comes to you the greater the disparity is between the two images.
Pen together two eyes- try with one
MONOCULAR CUES
Interposition: if something is blocking our view, we perceive it as closer.
• Relative Size: if we know that two objects are similar in size, the one that looks smaller is farther away.
• Relative Clarity: we assume hazy objects are farther away.
MORE MONOCULAR CUESTexture Gradient: the coarser it looks the
closer it is.
• Relative Height: things higher in our field of vision, they look farther away
• Relative Motion: things that are closer appear to move more quickly.
• Linear Perspective: Parallel lines seem to converge with distance.
• Light and Shadow: Dimmer objects appear farther away because they reflect less light.
PERCEPTUAL ADAPTATION
In vision, the ability to adjust to an artificially displaced or even inverted visual field.
CONTEXT EFFECTS
Based on immediate context, not schemas. You do not hear the word, but can guess at it
based on the context it was said in.
MOTION PERCEPTION We perceive motion incredibly well. We judge mostly by the size of the object.
Think about how cartoons work.
PHI PHENOMENON
An illusion of movement created when two or more adjacent lights blink on and off in succession.
THE END If you assume your senses give you an accurate
and undistorted picture of the world, you are probably wrong. If you don’t believe me, try this.
Silently read the backwards statement below. Flip if over in your mind. What does it say?
.rat eht saw tac ehT
ANSWER How many people saw this:
The cat saw the rat.
Look at it again:.rat eht saw tac ehT
How many people saw this: The cat was the rat.
Answer:The cat was the tar.
ERNST WEBER (1795 – 1878)
Anatomist / physiologist
introduced the “Just Noticeable Difference” (JND) concept expressed the
principle of difference threshold
GUSTAV FECHNER (1801 – 1887)
key figure in “Psychophysics” science of
quantitative relationships between sensation and their stimuli
expressed the JND as a mathematical formula and called it “Weber’s Law”
DAVID HUBEL (1926-2013) / TORSTEN WIESEL (1924 - ????) researched visual sensation / perception Nobel Prize (Physiology/Medicine) for their work
discovering feature detectors
CRASH COURSE (VIDEO: 10:45)
Video Link http://www.youtube.com/watch?v=unWnZvXJH2o
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