AP Psych Unit 3
Sensation and Perception Principles
Synesthesia - to “perceive together,” is a condition in which two senses are sensed at the same time, where on type of stimulation evokes the sensation of another
Sensation “Detection and Encoding” - the senses collect some kind of information from the environment and convert it to a signal that can travel to the brain
Sensing our environment through touch, taste, sight, sound, and smell (nervous system)
Our sense depend on each other
Transduction - the transformation of stimulus energy to electrochemical energy of neural impulses (except smell)
Conversion of one form of energy to another
Perception “Interpretation” - process by which we select, organize, and interpret sensory information in order to recognize meaningful objects and events
Information is organized, interpreted, and consciously experienced
Enables recognition of meaningful events
The brain is an isolated chamber, never exposed to the physical world but creating our reality
Bottom-Up Processing “Sensory Analysis” - involves starting with an incoming stimulus and working upwards until a representation of the object is formed in our minds
Begins at entry level with what our senses can detect
Requires no previous knowledge or learning
Top-Down Processing - form our perceptions starting with a larger object, concept, or idea before working our way toward more detailed information
Big Picture - Tiny Details
Influenced by prior experience and current expectations
Prosopagnosia - face blindness; some people don’t even know they have this
Deficiency in top-down processing
Absolute Threshold - smallest level of stimulus that can be detected, usually defined as at least half time (point something becomes noticeable)
How dim a light be or how soft can a sound be and still be detected half the time
Signal Detection Theory - theory predicting how and when we detect the presence of a faint (weak) stimulus (signal) amid background stimulation (noise)
Assumes there is no single absolute threshold, detection depends partly on a person’s experience, motivation, and level of fatigue
Subliminal Sensation - when stimuli are below one’s absolute threshold for conscious awareness
Much of our information processing occurs automatically, out of sight, off the radar screen of our conscious mind
Difference Threshold “Just Noticeable Difference (JND)” - the amount something must be changed in order for a difference to be noticeable, or detectable at least half the time
Weber’s Law - the principle that, to be perceived as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount)
Bigger stimuli require larger differences to be noticed
Sensory Adaptation - reduction in sensitivity to a stimulus after constant exposure to it
Reduces our awareness of a constant stimulus, it helps free up our attention and resources to attend to other stimuli in the environment around us
Selective Attention - we center our attention on certain important elements of our environment while other things blend into the background or pass us by completely unnoticed
We sense a LOT of information. Scientists estimate we observe 11,000,000 bits of info per second. But we weed out all but 40 bits
Divided Attention “Multitasking” - occurs when mental focus is on multiple tasks or ideas at once
Divided attention does decrease the amount of attention being placed on any one task or idea if there are multiple focuses going on at once
Cocktail Party Effect “Filter and Focus” - Ability to focus on a particular sound while partial filtering out other sounds
Happens not just at cocktail parties but also in virtually any environment
Awareness of background “buzz” but limited semantic processing
Inattentional Blindness - When our focus is directed at one stimulus (relevant to us), leaving us blind to other stimuli
Rather than focusing on every tiny detail in the world around us, we tend to concentrate on things that are most important
Change Blindness - the tendency to people have to miss charges in their immediate visual environment
People are capable of missing both minor and major changes that take place right in front of them
The Science of Seeing
As humans, we can perceive less than a ten-trillionth of all light waves
The wavelength of light determines the color so with a properly with a properly functioning eye and brain, the color we all see is the same
A large part of our brain is devoted to processing visual input
Parts of the Eye
Cornea - Transparent, dome-like structure on the front part of the eye, gives the eye focusing or refracting power
Pupil - The adjustable opening in the center of the eye through which light enters, controls the amount of light that enters into 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 (colored part of eye)
Crystalline Lens - The transparent structure behind the pupil that changes shape to help focus images on the retina, focus eye on near or far objects
Retina - Light-sensitive layer that lines the back of the eye
Retina contains photoreceptors that absorb light and then transmits those signals through the optic nerve to the brain
Photoreceptors - convert light energy to electrochemical neural impulses that are conducted to our brain
Photoreceptors are called Rods and Cones
Our retina contains 120 million rods and about 1 million code photoreceptors
Cones - Light-detecting cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions, directly involved in our ability to perceive color
Red - 60%
Green - 30%
Blue - 10%
Rods - Specialized photoreceptors that work well in low light conditions, involved in our vision in dimly lit environments as well as in our perception of movement on the periphery of our visual field
Blind Spot - the point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there
Saccade, eyes have rapid movement from side to side to help fill in missing information created by the blind spot
Young-Helmholtz Trichromatic (three-color) Theory - There are three receptors in the retina responsible for the perception of color (green, blue, red)
Colors red, blue, and green can be combined to create all colors of light
Color-Deficient Vision They simply lack functioning red-or green-sensitive cones or sometimes both, missing cones that response to a specific color
Monochromatic (one-color) or dichromatic (two-color) instead of trichromatic, making it impossible to distinguish the red and green
Opponent-Process Theory - retinal processes only occur in 3 sets of opponents
Red-Green Complex
Blue-Yellow Complex
Black-White Complex
Cells can only detect the presence of one color at a time because the two colors oppose one another
Afterimage - describes the continuation of a visual sensation after removal of the stimulus
Feature Detectors - in the visual cortex, specialized neurons that react to the strength of visual stimuli, responding to shapes, angeles, edges, lines, and movement in field of vision
The Hearing Sense
Audition - the biological process by which our ears process sound waves
In order for something to be a sound, it has to be perceived
Evolutionary, being able to hear approaching predators or prey in the dark, helped increase chances of survival
Sound Waves - vibrations of molecules that travel through air
Sound waves result from the mechanical vibration of molecules from a sound source
The vibrations move in a medium, such as air, outward from the source, first compressing molecules then letting them move apart
Amplitude - height of the sound wave (greater compression), the psychological quality of loudness
The intensity or power of sound is measured using a scale of decibels
Decibels at 120 or higher can cause immediate damage to one’s hearing and one’s eardrum will rupture at 150 dB
Frequency - the number of wavelength cycles in a unit of time, measured using hertz, determines the highness or lowness of the sound (pitch)
Sound is perceivable by humans only in a range from 20 hertz (Hz) to 20,000 Hz
Shorter wavelength, higher frequency, higher the pitch
Longer wavelength, lower frequency, lower the pitch
Pinna - The outer ear, the visible part of the ear (opening unto the head) that protrudes from our heads (design to catch sound waves)
Pinna direct sound waves into the ear canal (auditory canal)
Tympanic Membrane - The eardrum, Sound waves make the eardrum vibrate (conduction)
Middle Ear - sound waves travel to vibrate the bones (auditory ossicles) of the ear
Unbreakable bones, malleus (hammer), the incus (anvil), and stapes (stirrup)
These bones concentrate the vibrations of the eardrum on the coechlea's oval window
Inner Ear: The innermost part of the ear
Cochlea, A coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses
On the top of this membrane is the organ of Corti which contains hair cells (convert vibrations into nerve impulses and send to auditory nerve
From the auditory nerve, the new neural signals travel throughout your medulla, pon, and thalamus (sensory relay station) to temporal lobe auditory cortex where your brain perceives and makes sense of what you just heard
Place Theory - In hearing, explain how we how we distinguish high-pitched sounds that possess a frequency that exceeds 5,000 hertz
We hear pitch based on WHERE on the basilar membrane the hair cells vibrate
Different parts of the cochlea are activated by different frequencies
Locating Sound “Sound Localization” - Sound waves strike one ear sooner and more intensely than the other. From this information, our nimble brain computes the sound’s location
Using parallel processing, your brain processes both intensity differences and timing difference to determine where the sound is
Conduction Hearing Loss - Hearing loss caused by structural damage (eardrum is punctured) to the mechanical system that conducts sound waves to the cochlea
Age, genetic predisposition, environmental effects, exposure to extreme noise, certain illnesses
Common as people get older, but hearing aids can compensate for the loss
Cochlear Implant - A device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea
If an implant is to be effective, they cannot delay the decision until their child reaches the age of consent
McGurk Effect - interaction with vision and hearing an illusion that when auditory component of one sound is paired with the visual component of another sound leading to a third sound
The Other Senses
Taste and smell are chemical molecules are chemical senses that detect chemicals in the environment
Taste (Gustation) - the tastes that we perceive are a two-phase chemical reaction that involves both our mouth and throat (taste) as well as our nose (smell)
Four basic groupings, sweet, salty, sour, and bitter
Saliva plays an important role in transporting that tastes we perceive into our taste buds
Umami - Japanese word similar to savory or delicious. It is actually related to the taste of glutamate and is similar to the taste of broth. This flavor is said to elicit an emotional response
Smell (Olfaction) - chemical molecules breathed in through the nose
Smell receptors lie in the top of the nasal passage
They send impulses along the olfactory nerve to the olfactory bulb, a structure in the limbic system
Our sense of smell is responsible for about 80% of what we taste
Without our sense of smell, our sense of taste is limited to only five distinct sensations: all other flavors that we experience come from smell
Somesthetic Senses - the senses of the skin, allow us to feel light touch, pressure, pain, cold, and warmth
Inside the skin there are several different kind of cells that sense pressure (skin = largest sense organ)
Signals received by the receptors are sent to the thalamus and to somatosensory cortex in parietal lobe
Kinesthesis - the system for sensing the position and movement of individual body parts
Sensors in your joints, tendons, bones, and ears, as well as your skin sensors
People have a vestibular sense that monitor’s your head’s position and movement (therefore it also monitor’s your body’s position and movement)
Pain - the body’s warning sign that something isn’t right (many varieties and intensities) combine both bottom-up sensations and top-down processes
Pain is necessary for survival, but our brain can stop it if it needs to
Gate-Control Theory of Pain - There is a “gate” in the spinal cord that switches pain on and off, the more neurons fire in response to pain the more intense the pain
One way to treat chronic pain is to stimulate (by massage, by electric stimulation, or by acupuncture) “gate-closing” activity in the large neural fibers
When we are distracted from pain (a psychological influence) and soothed by the release of endorphins, our natural painkillers (a biological influence), our experience of pain may be greatly diminished
People who carry a gene that boosts the availability of endorphins are less bothered by pain, and their brain is less responsive to pain
The brain can also create pain, as it does in people’s experiences of phantom limb sensations
7 in 10 amputees may feel pain or movement in nonexistent limbs
We feel, see, hear, taste, and smell with our brain, which can sense even without functioning senses
Perceptual Organization
Gestalt Psychology - the whole is greater than the sum of its parts
Gestalt Psychologists - Emphasized the brain’s tendency to integrate pieces of information into meaningful wholes
Gestalt, German word for “form” or a “whole”
In perception, the whole may exceed the sum of its parts
Our brain does more than register information about the world
Figure-Ground Pattern - Tendency of the visual system to simplify a scene into the main object that we are looking at (the figure) and everything else that forms the background (or ground)
Grouping - brains have a tendency to organize stimuli into groups in order to to process the complexity of the world
Depth Perception - the ability to perceive the world in three dimensions (3D) and to judge the distance of objects
Depth perception is achieved when the brain processes different pictures from each eye and combines them to form a single 3D image
Binocular Cues - are those that require the use of both eyes (integrated by the brain) in order for us to perceive depth or distance
Retinal Disparity - the difference between the visual images that each eye perceives because of the different angles in which each eye views the world
The images overlap in the center, and the brain connects these together into one seamless view
Convergence - our eyes move together to focus on an object that is close and that they would move farther apart for a distant object
Enables us to determine how near or far things are away from us
Molecular Cues - clues that can be used for depth perception that involves using only one eye. How we form 3D from 2D
Linear Perspective - depth cue that makes parallel lines appear to converge at a vanishing point on the horizon
The closer together the two lines are, the greater the distance will seem
Interposition Overlap - when one object overlaps another, the object that is partially obscured is perceived as being farther away
Relative Size - if two objects are roughly the same size, the farther away object will appear smaller even though the objects are still the same size
Relative Height - we perceive objects higher in our visual field as being further away and those that are close should appear lower
Relative Clarity - we perceive hazy objects as farther away than sharp, clear objects
The farther something is from us, the less detail it conveys
Light and Shadow - objects that are darkened and obscured may appear further off in the distance than those that are brightly lit
Nearby objects reflect more light into our eyes more than distant objects
Texture Gradient - method of determining the depth by noting that distant objects have a smoother texture than nearby objects
Relative Motion - As you're moving, objects that are closer seem to zoom by faster than do objects in the distance
Perceive the fast moving objects in the foreground as closer than the slower moving objects off in the distance
Perceptual Set - predisposition to perceive things in a certain way
We often tend to notice only certain aspects of an object or situation while ignoring other details
Perceptual Constancy “Top Down Process” - The tendency to perceive an object you are familiar with as having a constant shape, size, and brightness despite the stimuli changes that occur
Our brain constructs our perceptions.
Color Constancy - the tendency of objects to appear the same color even under changing illumination
Perceptual phenomenon, the result of mechanisms in the eye and brain
Lightness Constancy “Brightness constancy” - We perceive an object as having a constant lightness even while its illumination varies
We perceive objects not in isolation but in their environmental context
Shape Constancy - constancy, we perceive objects as having a constant size, even while our distance from them varies or despite differences in viewing angle
Parapsychology - the study of paranormal phenomena, including ESP and psychokinesis
Falsely claims the legitimacy of extrasensory perception or ESP (perception without specific sensory input)
All the research indicates that ESP is not possible