Myers' Psychology for AP Second Edition Unit 4: Sensation and Perception 

Module 16: Basic Principles of Sensation and Perception 

Selective Attention 

• Your awareness focuses through selective attention 
• The senses take in 11,000,000 bits of information but humans are only actively aware of 40. For example, you understood this sentence through your visual senses but your sense of touch and brain are not processing the feeling of your clothes on your back 
• In a party you often can only hear one voice at a time because that is all your brain can process at the moment 

Selective Attention and Accidents: 

• When doing multiple activities at once your selective attentions goes back and forth between the two 
• This can be dangerous in situations such as driving. If you do not give the road your full attention, accidents can and will occur 

Selective Inattention: 

• Inattentional blindness occurs when you don't see something obvious because your attention was elsewhere 
• This shows that humans are really good at focusing on one thing at a time 
• Magicians use misdirection to fool people. They also use change blindness by directing attention to one area. The audience focuses on that area and does not see what is going on in the rest of the environment 
• Often times these stimuli are drawn out by something unusual, like an angry face in the crowd 

Transduction

• All senses receive sensory stimulation from specialized receptor cells, transform said stimulation into neural impulses, and deliver the information on the brain 
• The process of converting energy into something the brain can use is called transduction 

Thresholds

• Our senses are restricted to all the different light and sound waves around us 
• Bats use sonar to find food, but humans have no way to create this usage 
• All of the energies we can see and hear are enough for humans to survive 

Absolute Thresholds: 

• Humans are extremely sensitive to certain kinds of stimuli 
• Absolute thresholds are the awareness of faint stimuli 
• Being able to detect a weak stimuli depends on the signal's strength as well as our psychological state
• The signal detection theory predicts when we will pick up different signals 
• If you cannot detect a stimuli more than 50% of the time, it is called subliminal 
• Stimuli are still in work even if we are unaware of it 

Difference Thresholds: 

• The difference threshold is the minimum difference a person can detect between stimuli 
• The difference threshold increases based on the size of the stimuli 
• Weber's law states that a person can detect a difference because the two stimuli differ by a constant percentage 
• For example, lights must differ by 8% for humans to notice that they are not the same

Sensory Adaptation 

• Sensory adaptation happens when you are exposed to unchanging stimuli for long periods of time. The longer you stay you become less aware of the sense because your nerve cells fire less often 
• Objects do not vanish from our sight because our eyes are constantly moving 
• Sensory adaptation gives us the ability to focus on information changes without being distracted 
• Sensory adaptation influences our perception of emotions

Module 17: Influences on Perception 

Perceptual Set

• A perceptual set is mental tendencies and assumptions that greatly affect what we perceive 
• For example, the picture of the rabbit-duck. Depending on your perceptual set will determine if you see the duck or the rabbit first
• Perceptual sets can also affect hearing and taste 
• Pre-existing schemas influence how we interpret sensations 
• Gender stereotypes are also influenced by perceptual sets. Seeing a blue toy will make you think the baby is a boy, but it very well be a girl  

Context Effects 

• Stimuli triggers differ based on context 
• Given the phrase "eel is on the wagon" the brain is able to work backwards and understand that "eel" is really "wheel" 

Emotion and Motivation 

• Perception is also influenced by our emotions 
• If you are listening to sad music and then hear the word "morning" you might mistake it for the homophone "mourning" 
• Motive also matters. If you are thirsty a nearby water bottle will seem closer 

Module 18: Vision 

The Stimulus Input Light Energy 

• When you see something that is red, you are actually seeing the pulses of electromagnetic energy that is perceived as red 
• Different organisms can perceive more or less colors than humans
• Wavelength is the distance from one wave peak to the next 
• Wavelength determines the hue (color)
• Intensity is the amount of energy in light waves
• Intensity is determined by a waves height (amplitude) 
• Intensity influences brightness  

The Eye

• Light enters the eye through the cornea 
• The cornea protects the eye and bends light to allow focus 
• The pupil is a small adjustable opening where light enters. It is the black dot in the middle of the eye  
• The iris is the colored portion of the eye that surrounds the pupil. It is a muscle that dilates or constricts in response to light intensity. The iris can also respond to emotion 
• The lens is located behind the pupil. It changes light rays into an image on the retina by changing the curvature through accommodation 
• The retina is a tissue located on a sensitive inner surface  
• The retina does not see a whole image but its receptor cells convert the light particles into impulses. These impulses go to the brain where they reassemble into a image 

The Retina:

• The rods and cones are the retina's outer layer of cells 
• Light energy triggers chemical changes that activate bipolar cells. The bipolar cells activate ganglion cells
• The ganglion cells form the optic nerve 
• The optic nerve carries information to your brain
• The spot where the optic nerve leaves the eye is called the blind spot. There are no receptor cells in this area 
• The fovea is the retina's central focus area. 
• Cones are often found in and around the fovea 
• Cones send their own bipolar messages 
• Rods change bipolar cells with other rods 
• Cones allow us to see color 
• Rods enable black-and-white vision 

Visual Information processing 

• Information begins processing in the retina 
• The retina encode and analyze sensory information
• The information gets sent to the rods and cones where they send it to bipolar cells 
• The bipolar cells send it to the ganglion cells which make up the optic nerve 
• Sensitivity also cases retinals to misfire information 

Feature Detection: 

• Feature detectors are nerve cells that respond to specific features like shape or angles
• Feature detectors are located in the occipital lobe's visual cortex 
• The cells pass on information to other cortical areas 

Parallel Processing: 

• Parallel processing is doing many things at once (multitasking) 
• When looking at a visual scene the brain processes motion, form, depth, and color at the same time 
• Your brain compares what you are seeing to information already stored in your brain. This allows you to recognize a face 

Color Vision 

• A tomato is not actually red. It rejects the long red wavelengths, which causes the red to reflect off of the tomato. Light also has no color, but is influenced by our brain 
• About 1/50 people (and usually a male) have color deficiency. They cannot see as many colors as the rest of us 
• Any color can be created by combining the lightwaves of red, blue, and green 
• People who are color-blind lack either the red or green cones 
• If you stare at a green square for 30 seconds and then look at a blank sheet of paper, you will see a red square which is green's opponent color
• Some neurons are turned on by the color red while others are turned off 
• Color processing occurs in two stages. The first deals with the retina's cones responding to different stimuli. Then their signals are processed in the nervous system where they turn certain neurons on and off

Module 19: Visual organization and Interpretation 

Visual Organization 

• When given a cluster of sensation, people organize the sensations into a gestalt 
• A gestalt is an organized whole 
• We organize sensations into perceptions 

Form Perception

Figure And Ground: 

• The first perceptual task is perceiving an object as something different than its surroundings 
• The object is the "figure" and the surroundings are the "ground" 
• The figures can change, but they will always be distinct from the ground 

Grouping: 

• The next step is to organize figures into something meaningful
• Color, movement, and contrast get processed automatically 
• Next the brain follows three rules of grouping; proximity, continuity, and closure 
• Proximity is grouping nearby figures 
• Continuity is perceiving smooth patterns rather than harsh, broken lines
• Closure fills in gaps to create whole objects 

Depth Perception: 

• Depth perception allows us to estimate an object's distance 
• We are able to estimate how far away something is, both im distance and height 
• Depth perception is partially innate 

Binocular Cues: 

• Binocular cues require both eyes in order to perceive certain depths 
• Your retinas receive slightly different images and you brain compares these images to determine the depth of an object 
• Retinal disparity is the difference between two images
• The greater the retinal disparity, the closer an object is 
• When the distance is greater, the retinal disparity is smaller 

Monocular Cues: 

• Monocular cues occur when an object is too far away to depend on binocular cues
• Monocular cues can rely on each eye individually 

Motion Perception: 

• If you could not see motion you would not be able to walk, eat, drive, or write
• Your brain assumes that shrinking objects are going away from you and enlarging objects are getting closer to you 
• Large object appear to move slower than small objects
• Continuous movement of multiple images is what makes it see like animated characters are moving 

Perceptual Constancy

Color And Brightness Constancies: 

• The color of an object depends on its context 
• The color of an object can change slightly, usually to a different shade, depending on the lighting 
• Color constancy is when an object remains the same color even if the lighting changes 
• Brightness constancy (also known as lightness constancy) also depends on context 
• Objects tend to have constant brightness
• Relative luminance is the amount of light an object reflects relative to its surroundings 
• Comparison can change and control our perceptions 

Shape And Size Constancies: 

• An object's shape can change depending on the angle you look at it. But the object itself will never change 
• Shape constancy allows us to see the form of objects as constant 
• Size constancy allows us to see objects at the same size, even when their distance varies 
• The size-distance relationship explains why the moon looks larger across the horizon than it does higher in the sky 

Visual Interpretation 

• Immanuel Kant argued that we are born with ways of organizing sensory experiences
• John Locke argued that through experiences we learn how to perceive the world 

Experience and Visual Perception

Restored Vision and Sensory Restriction: 

• Blind people who have gained sight cannot visually recognize objects they know by touch 
• They can distinguish color and brightness but not shape 
• Experience guides and maintains neural organization in the brain. It is a pathway that affects perception 
• Earlier experiences help shape perceptions that last a lifetime 

Perceptual Adaptation: 

• Perceptual adaptation is when changes in visual input are made so that the world seems normal again
• For example, when you get a new pair of glasses. When you first put them on you may feel dizzy, but after a few days you adjust 

Module 20: Hearing 

The Stimulus Input Sound Waves 

• Sound waves cause air molecules to move. The molecules will bump into each other and create compressed or expanded air 
• Sometimes we can even feel the vibrations 
• The amplitude of a soundwave determines how loud it is 
• The length of a soundwave is called frequency 
• Frequency determines the pitch 
• Sounds are measured in decibels
• 0 decibels represent the absolute threshold for hearing  

The Ear 

• Hearing begins when sound waves enter the outer ear
• The waves start in the outer ear and then travel through a auditory canal to the eardrum. The eardrum vibrates when the sound waves reach it  
• The middle ear is made up of three bones; the hammer, anvil, and stirrup 
• The middle ear will then take the vibrations to the cochlea 
• The cochlea is located in the inner ear 
• When the vibrations reach the cochlea it causes the fluid inside of it to move. This causes the basilar membrane to move hair cells 
• The hair cells trigger impulses in the nearby nerve cells. These form the auditory nerve which send neural messages to the auditory cortex of the brain 
• If someone would damage the cochlea's hair cells or nerves the could suffer from sensorineural hearing loss. This is also known as nerve deafness. This can be caused by heredity, aging, and exposure to ear-splitting noise 
• Conduction hearing loss is less common. It is caused by damage to the mechanical system that takes sound waves to the cochlea 
• Hearing loss often comes from exposure over long periods of time 
• Those with nerve deafness can get a cochlear implant to help them hear 
• Cochlear implants are mostly used in children and can allow them to understand oral communication well   

Perceiving Loudness: 

• The brain interprets loudness based on the number of activated hair cells 
• Loud sounds still sound loud to people who are losing their hearing 
• Implants often amplify soft sounds rather than loud ones 

Perceiving Pitch: 

• The place theory states that we hear different pitches because different sound waves trigger different places along the cochlea's membrane 
• The brain recognizes pitch by recognizing what part of the membrane is being triggered 
• High frequencies produce large vibrations towards the start of the cochlea's membrane 
• The place theory can explain how we hear high-pitched sounds but not low-pitched ones
• The frequency theory states the brain is able to read pitch by watching the frequency of neural impulses as they travel through the auditory nerve
• This means a sound wave that has a frequency of 100 waves per second would produce 100 pulses per second 
• However, an individual neuron cannot fire more than 1000 times per second, so this theory does not explain how we hear frequencies above 1000 waves per second 
• The volley principle believes that neural cells alternate firing 
• Through rapid succession the achieve a combined frequency above 1000 waves per second    

Locating Sounds: 

• The placement of the ears allows us to have stereophonic hearing 
• If there is a noise coming from your right, your right ear will hear a more intense sound and will hear it sooner than your left ear 
• However, the differences are not very noticeable 

Module 21: The Other Senses 

Touch 

• Touch allows us to convey all sorts of emotion 
• The sense of touch is a mix of senses of pressure, warmth, cold, and pain 
• The brain is most sensitive to unexpected stimulation. This is why you can't tickle yourself but someone else can tickle you 

Pain

• Pain is the body's way of saying "something is wrong" 
• People born without the ability to feel pain can experience severe injuries and not receive proper help, causing the injury to be even worse 

Understanding Pain: 

• Women are more pain sensitive than men 
• Genes, physiology, experience, and attention all play into how pain sensitive we are 

Biological Influences: 

• There are different nociceptors that detect hurtful temperatures, pressures, or chemicals 
• The gate-control theory is the most useful model to understand pain
• It is theorized that the spinal cord contains a neurological gate. When tissue is injured, small fibers activate and open the gate, then you feel pain.
• Large fiber activity will cause the gate to close 
• Brain to spinal cord messages can also close the gate 
• Endorphins are natural painkillers 
• Sometimes people can feel pain in body parts that aren't there 

Psychological Influences: 

• Distractions can help forget that the pain is there or cause pain to go unnoticed when the injury first occurs 
• Our memory of pain is also edited 
• The memory remembers the pains peak moment and how much pain was felt at the end

Social-Cultural Influences: 

• We perceive more pain when people around us are also suffering from pain 
• When we feel empathy the brain may mimic the pain that the other person is feeling 

Controlling Pain: 

• To cope with pain many use drugs, surgery, acupuncture, massage, exercise, or relaxation training 
• Sometimes placebos can also help heal the pain 
• Distractions are some of the best ways to forget about the pain 

Taste

• The 5 senses of taste are sweet, sour, salty, bitter, and the meaty taste called umami 
• Taste is a chemical sensation 
• Aversive taste moves us away from new foods because they might be toxic 
• As you get older, your number of taste buds decreases. This means you begin to lose your sense of taste 
• Smoking and drinking alcohol are other factors that can lead to early taste loss 
• Expectations also lead to taste. If your meal is very expensive you expect it to taste much better than a cheap fast food item 

Smell 

• Smell is a chemical sensation 
• When you smell something, your olfactory receptor cells respond selectively 
• Odor molecules come in many shapes and sizes, so it takes many different receptors to detect them 
• When people have a good experience and remember the scent, they will like that scent 
• For example, peppermint is a good smell because people associate it with Christmas 
• This also works the opposite way with negative emotions 

Body Position and Movement 

• Your kinesthesia is your sense of position and movement of your body parts
• Kinesthesia is influenced by your joints, tendons, and muscles 
• Vision interacts with kinesthesia. It is much harder to do certain tasks with your eyes closed 
• Vestibular sense detects your head's position and movement 
• The semicircular canals and vestibular sacs are filled with liquid. This liquid moves around when your head tilts or rotates 

Sensory Interaction 

• The brain combines all of the information our senses are getting in order to interpret the world
• Sensory interaction is the principle that one sense influences another  
• Smell, texture, and taste all interact when eating 
• Sometimes our senses disagree. You may see a person say "ga" but hear them say "ba" which leads your brain to combine the two and get "da"
• The brain can blend tactile and social judgments 
• Some individuals have synesthesia where one sense produces another. For example, hearing a sound causes you to see a color 

Vocabulary: 

Sensation- the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment 

Perception- the process of organizing and interpreting sensory information, enabling us to recognise meaningful objects and events 

Bottom-up processing- analysis that begins with the sensory receptors and works ip to the brain's integration of sensory information 

Top-down processing- information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations 

Selective attention- the focusing of conscious awareness on a particular stimulus 

Inattentional blindness- failing to see visible objects when our attention is directed elsewhere

Change blindness- failing to notice changes in the environment 

Transduction- conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brain can interpret

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

Absolute threshold- the minimum stimulation needed to detect a particular stimulus 50 percent of the time 

Signal detection theory- a theory predicting how and when we detect the presence of faint stimulation (signal) amid background stimulation (noise). Assumes that there is no single absolute threshold and that detection depends partly on a person's experience, expectations, motivation, and alertness 

Subliminal- below one's absolute threshold for conscious awareness

Priming- the activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response 

Difference threshold- the minimum difference between two stimuli required for section 50% of the time. We experience the difference threshold as a just noticeable difference (or jnd) 

Weber's law- the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather that a constant amount) 

Sensory adaptation- diminished sensitivity as a consequence of constant stimulation 

Perceptual set- a mental predisposition to perceive one thing and not another 

Wavelength- the distance from the peak of one light or sound wave to the peak of the next. Electromagnetic wavelengths vary from short blips of cosmic rays to the long pulses of radio transmission 

Hue- the dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forth 

Intensity- the amount of energy in a light or sound wave, which we perceive as brightness or loudness, as determined by the wave's amplitude 

Pupil- the adjustable opening in the center of the eye through which light enters

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 

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

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 

Accommodation- the process by which the eye's lens changes shape to focus near or far objects on the retina 

Rods- retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don't respond

Cones- retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. The cones detect fine detail and give rise to color sensations 

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

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

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

Feature detectors- nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement 

Parallel processing- the processing of many aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision. Contrasts with the step-by-step (serial) processing of most computers and of conscious problem solving 

Young-Helmholtz trichromatic (three-color) theory- the theory that the retina contains three different color receptors---one most sensitive to red, one to green, one to blue---which, when stimulated in combination, can produce the perception of any color 

Opponent-process theory- the theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green 

Gestalt- an organized whole. Gestalt psychologists emphasized our tendency to intergrate pieces of information into meaningful wholes 

Figure-ground- the organization of the visual field into objects (the figures) that stand out from their surroundings (the ground) 

Grouping- the perceptual tendency to organize stimuli into coherent groups 

Depth perception- the ability to see objects in three dimensions although the images that strike the reina are two-dimensional; allows us to judge distance 

Visual cliff- a laboratory device for testing depth perception in infants and young animals 

Binocular cues- depth cues, such as retinal disparity, that depend on the use of two eyes

Retinal disparity- a monocular cue for perceiving depth: By comparing images from the retinas in the two eyes, the brain computes distance---the greater the disparity (distance) between the two images, the closer the object 

Monocular cues- depth cues, such as interposition and linear perspective, available to either eye alone

Phi phenomenon- an illusion of movement created when two or more adjacent lights blink on and off in quick succession 

Perceptual constancy- perceiving objects as unchanging (having consistent shapes, sizes, brightness, and color) even as illumination and retinal images change

Color constancy- perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object 

Perceptual adaptation- in vision, the ability to adjust to an artificially displaced or even inverted visual field 

Audition- the sense or act of hearing 

Frequency- the number of complete wavelengths that pass a point in a given time (for example, per second) 

Pitch- a tone's experienced highness or lowness; depends on frequency 

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

Cochlea- a coiled, bony, fluid-filled tube in the inner ear; sound waves traveling through the cochlear fluid trigger nerve impulses 

Inner ear- the innermost part of the ear, contains the cochlea, semicircular canals, and vestibular sacs 

Sensorineural hearing loss- hearing loss caused by damage to the cochlea's receptor cells or to the auditory nerves; also called nerve deafness

Conduction hearing loss- hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea 

Cochlear implant- a device for converting sounds into electrical signals and stimulation the auditory nerve through electrodes threaded into the cochlea 

Place theory- in hearing, the theory that links the pitch we hear with the place where the cochlea's membrane is stimulated 

Frequency theory- in hearing, the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, this enabling us to sense its pitch 

Gate-control theory- the theory that 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 a nerve fibers and is closed by activity in larger fibers or by information coming from the brain 

Kinesthesia- the system for sensing the position and movement of individual body parts

Vestibular sense- the sense of body movement and position, including the sense of balance 

Sensory interaction- the principle that one sense may influence another, as when the smell of food influences its taste 

Embodied cognition- in psychological science, the influence of bodily sensations, gestures, and other states on cognitive preferences and judgments