Sensation and Perception

Sensation and Perception

Term

/ Explanation / Application/Example/Extension

Sensation

/ Sensation is the process of using senses to detect or sense information from the environment / Your eyes detect light waves, your ears detect sound waves, your skin detects pressure
Processes of Sensation / Bottom-up processing is an information processing the begins with the senses and then goes to the brain / Remember information is sent from the bottom up to the brain.
Transduction is the process of converting physical energy from the environment into neural code to be interpreted by the brain / The brain communicates with the body through neural communication by utilizing action potentials and the release of neurotransmitters.
Absolute threshold is the minimum stimulation necessary to detect an environmental stimulus / An action potential cannot occur until there is a minimum amount of stimulation necessary that exceeds the threshold- this depends on the strength of the stimulus
Difference threshold- also called the just noticeable difference- is the minimum difference that is needed to detect a difference between 2 stimuli / In order to detect a difference between a person’s voice and the background noise of a classroom, there has to be enough of a difference or you will not be able to hear the person talking.
Weber’s law states in order to detect a difference between 2 stimuli, then the stimuli must differ by a constant proportion / If the classroom noise gets louder then by proportion, so does the person’s voice, in order to compete with the increase of the classroom noise. A teacher has to talk louder to compete with the nose of the classroom.
Signal detection theory is a set of formulas which predicts that we can detect a stimulus depending on the strength of the stimulus, the environment, and person detecting the stimulus / If a student is to detect a teacher’s voice, then the teacher’s voice has to be (1) loud enough, or exceed the absolute threshold, the (2) the classroom noise, or environment has to be in proportion to the teacher’s voice (cannot be louder to the teacher’s voice), and (3) the student has to be focused on the teacher’s voice through being motivated to listen.
Selection attention is focusing attention on the particular stimulus
Sensory adaptation is diminished sensitivity as a result of constant exposure to stimulus / When you first jump into a pool it is cold, then over a period of time, or constant exposure to the water, the person’s senses adapt to the cool temperature of the water. (The temperature of the water did not change- the senses adapted- or got used to the water temperature)

What we See

/ Hue refers to color, which is determined by the length of a wave. / Wavelength- is indicated from one peak of a wave to the following peak / Long wavelengths produce reddish colors / Medium wavelengths produce greenish colors / Short wavelengths produce bluish colors
Intensity, or brightness of a color, is determined by the height of a wave, referred to as amplitude
Great amplitude or taller waves produce brighter colors / The taller the wave the brighter the color. Think about staring up at a roller coaster- the higher you look up, the brighter it gets
Small amplitude or smaller waves produce dull colors

The Eye

/ Parts of the Eye / Cornea protects the eye and begins to bend light waves
Iris is the colored portion of the eye that controls the size of pupil / The iris constricts, which makes the size of the pupil smaller, in response to bright light because too much light entering the pupil at once could damage the retina. / When it is dark out the iris expands, allowing more light to enter the pupil therefore allowing enough stimulation to exceed the threshold and cause an action potential
Pupil- is the opening in the eye that allows light to enter
Lens is the part of an eye that focuses on an object / The lens is like a camera
Accommodation refers to the process of how the lens focuses in and out of an object
Retina is the part of an eye where the process of transduction takes place through the use of the sensory receptors rods and cones (referred to as photoreceptors)
Rods are receptor cells that are stimulated in dim light or dark conditions; peripheral vision / Rods react to stimulation much slower than cones, which is why it takes longer to see objects in the dark. Rods also don’t detect fine details, which is why you just see the image of an object in the dark
Cones, located in the fovea, are stimulated, or turned on, in response to color and fine details / The fovea, where cones are stored, is in the center of the eye, which is why a person stares straight at an object to detect little details.
Bipolar cells gather information from the rods and cones and pass the information to the ganglion cells
Ganglion cells are bundles of axons that form the optic nerve, which sends information to the brain
Blind spot is where the optic nerve exits the back of the retina, which causes a blind spot in the visual field / You don’t detect this blind spot because both of your eyes accommodate for what the other eye does not detect
Optic chiasm- refers to the area of the brain where the optic nerves cross / The left part of the retina sends information through an optic nerve that carries the information to the right side of the brain where the primary visual cortex processes the information and the right part of the retina sends information to the left side of the brain
Feature detectors- are specialized cells that process specific visual features like shape, size, and angle of a stimulus / Think about using feature detectors to watch a motion-feature presentation- (movie)

Color vision

/ Theories of color vision / Trichromatic theory developed by Young-Helmholtz- states that we have 3 different types of cones, each sensitive to particular type of light wave, and through combinations of these cones being stimulated, we see color / When a person can’t see red, for example, it could be because he or she does not have red sensitive cones / Red sensitive cones detect long wavelengths- think of Clifford the dog
Blue sensitive cones detect short wavelengths- think of Smurfs
Green sensitive cones detect medium wavelengths- think of leprechauns
Opponent-process theory suggests that color is processed through pairs- red-green, blue-yellow, black-white / When a red cone is activated, then the green cone is off, which is why we don’t describe color as reddish-greenish. Also if you stare at a red dot for a while, then look away you will see a green dot, which is referred to as an afterimage.
Audition Hearing / What we Hear / Sound is the result of repetitive fluctuations of sound waves hitting, or bumping, into a medium like air. / Sound waves, unlike light wavelengths, can travel through objects- you can hear underwater, but because the sound waves bounce, or hit the water the sound of a stimulus is altered. Your mother’s voice does not sound the same underwater as it would if you were talking to her in your room.
Frequency refers to the number of complete wavelengths that pass a point
Pitch refers to the highness or lowness of a sound, which depends on frequency
Loudness depends on amplitude, which is the height of a wave- this is measured in decibels / Loudness is similar to brightness- the taller the wave the louder the sound, the smaller the wave, the softer the sound
Timbre is the complexity of a sound comprised of different frequencies and amplitudes.
Parts of the Ear / Outer ear contains the visible outer ear and the auditory canal. As sound waves enter the outer ear they are channeled to the eardrum. From the eardrum, the vibrations are sent to the middle ear. / Your outer ear is shaped the way it is to be able to best detect sound waves
Middle ear, located between the eardrum and the cochlea is considered the mechanical portion of the ear and contains 3 tiny bones (hammer, anvil, stirrup) that amplify sound waves and send then to the inner ear / Remember the middle ear HAS (hammer, anvil, stirrup) 3 tiny bones / People who have damage to the middle ear, which is referred to as the mechanical portion of the ear, experience conduction hearing loss. People with this type of hearing loss can benefit from a mechanical hearing aid, which does the job of the damaged middle ear
Inner ear, specifically the cochlea (part of the inner ear) is where transduction takes place / People who have damage to inner ear, called sensorineural hearing loss, often have permanent damage
Cochlea is a coiled, fluid-filled bony tube lined by the basilar membrane
Basilar membrane is the surface, or lining, of the cochlea. When the basilar membrane begins to move as a result of incoming vibrations, then the cilia begins to move.
Cilia- hair cells on the membrane that when moving cause neural impulses to travel up the auditory nerve to the brain / Think of cilia as tall grass- you can tell how windy it is by how fast the tall grass is moving- the faster the cilia moves, the louder the sound
Audition Theories / Place theory- what we hear depends on the place the vibration strikes the basilar membrane- higher frequencies at the beginning and low frequencies towards the end / The place theory is similar to playing a guitar, where you place your finger on the guitar chord will produce a different sound- same in terms of where the vibration strikes the basilar membrane
Frequency theory, also called Volley Principle- what we hear depends on the rate the impulse travels up the auditory nerve- higher frequencies faster rate / The frequency theory can be compared to shaking a rug- the harder you shake the rug, the more dust will come off- the higher the frequency, the faster the impulse will travel up the auditory nerve
Gustation (taste) Remember “that taste
disgustation” / Taste is a chemical sense, containing the taste bud receptor cells, sweet, salty, sour, bitter, which are located on the tongue. Each taste bud is sensitive to particular types of food
*Umami is considered to be a new taste bud, which is sensitive to high protein foods- like chicken- notice how many people think everything tastes like chicken* / Babies have a biological predisposition to like salty and sweet tastes making it more likely to like breast milk, which is a combination of these taste buds. On the other hand, babies have dislikes for sour and bitter tastes which could then protect them from poison
Taste receptors regenerate every 2 weeks, but decline naturally with age, especially for those who smoke and drink alcohol heavily, which is why these people prefer extra seasonings on their food- they are losing their sensation of taste over time.
Olfaction
(Smell)
Remember “old factories smell” / Smell is a chemical sense, achieved through olfactory receptor cells throughout the nasal lining
The olfactory receptor cells detect odors and send information to the olfactory bulb, which then sends the information to the temporal lobe and limbic system (remember the thalamus relays information for all senses except smell) / Smell information is directly sent, not relayed through, the thalamus to areas of the brain including the limbic system, which is why smell can quickly trigger memories, emotions, and thoughts
Unlike taste receptors, olfactory receptor cells do not regenerate, meaning that once damaged they are gone. Over time, these cells naturally decline.
Anosmia- refers to the inability to distinguish between different smells
Sensory interaction- smell and taste interact to detect information from the environment / When you have a cold and your sense of smell is affected, you probably notice during this time that food does not taste the same.
Somatic Senses (Body) / Different types of skin receptors are activated through specific types of stimulation- like pressure, warmth, and cold. However, there are no specific receptors for hot stimulations- the sensation of hot occurs when both the warmth and cold receptors are activated together / Majority of skin receptors are located on our hands and face, which is why when we get a pimple on our lip it hurts. The least amount of skin receptors are located on our back- a slap to the back is not as painful as a slap to the face
Frost bite can be described as burning because when we come inside we activate both warm (inside) and cold (from outside) receptors, which results in the sensation of hot
Gate-control theory is used to explain the sensation of pain, which states thatthe spinal cord contains a “gate” that either is open allowing pain signals to enter and continue to the brain, or be closed blocking the pain from going to the brain / The release of endorphins, a neurotransmitter that blocks pain, helps to close the “gate”, which is why pain medication helps ease pain signals from reaching the brain
The release of substance P, a neurotransmitter that reports pain, opens the “gate,” resulting in the sensation of pain
Kinesthetic senseis asensory system that monitors the position of individual body parts and movements and reports this information to the thalamus and cerebellum / When a person loses an arm or a leg due to an accident then that person would see a kinestologist, who would try to match a prosthetic limb to the rest of the body parts
Vestibular senseis a sensory system that monitors the head position and balance through receptors in the semicircular canals and the vestibular sacs located in the inner ear / When people get dizzy, they put their hands over their ears to regain balance

Perception

/ Perception is the process of organizing and interpreting sensory information / Perception is opinion, which is what accounts for differences among taste of foods, likes and dislikes concerning smells, sounds, etc. / We all use the same sensory organs to detect stimulation from the environment, but we all differ in our perceptions, which are influenced by memories, personality, and expectations.
Process of Perception / Top-down processing is based on your expectations and past experiences / If somebody told you right before you were take a bite of a burger that it was disgusting then that person’s opinion would have an affect when you tasted that burger
Perceptual set- is an example of top-down processing, which refers to our previous knowledge, or setof opinions about a particular object or topic
Parallel distributed processing states that the interpretation of a stimuli is based on several areas of the brain simultaneously working together / You are able to smell while visualize at a object at the same time due to parallel distributed processing
Gestalt Psychology / Gestalt psychologists studied how we perceive objects; emphasized that the whole is greater, or different than, the sum of its parts / A bike assembled, or put together looks different than the same bike broken into parts on the garage floor
Figure-ground relationship- we organize information by separating the “figure” from the “background” / The reason hunters wear camouflage is that animals are unable to separate the hunter (object- figure) from the woods (background- ground)
Grouping principles- our perception, or interpretation, depends on how we group objects
Similarity- group similar items / You would group all boys as one group of boys
Proximity- group items that are close together / People standing near one another are perceived as one group- “Hey, all of you standing over there”
Closure- looking at the whole; tend to fill in the gaps / If a circle was lit up by bulbs and a few bulbs were burned out, your brain would fill in the gaps
Continuity- once an object starts moving you perceive it as moving in same way / If you watched a car drive off, you would believe that the car continued in the same direction
Depth Perception / Depth perception is the ability to see in 3D
Visual cliff demonstration- a laboratory device, which showed that babies would not cross the clear glass placed between 2 structures, proving that depth perception is innate / Evolutionary psychologists believe that depth perception was innate because it helped to protect babies from danger- like falling.
Binocular depth cues- using 2 eyes
Retinal disparity- slightly different perception of images are produced because eyes are positioned on different parts of face / When you look at object with one eye and then with both eyes, the object looks slightly different
Convergence occurs when the eye muscles strain when an object comes too close / You experience convergence if you were to bring an object, like your finger, very close to your face
Monocular depth cues- using one eye
Relative size- objects appear larger when closer / Hold something close and then slowly pull it away from your face and the object will appear to become smaller- like a plane taking off
Relative motion- objects move slower when further away / When traveling in a car, the trees, which are further away, appear to be moving slower compared to sign posts that are closer to the car
Relative height- distant objects appear higher in visual field than closer objects / Mountains in the distance appear to be on top of lake, which you are standing in right in front of
Linear perspective- parallel lines seem to come together, or merge in the distance / If you were to look down a set of railroad tracks in the distance the tracks would appear to be coming together
Texture gradient- when an object is close you would be able to detect fine details; however, when an object is far away, you are not able to detect the details of that object. / From a distance, people or objects appear different- it is not until they are up close that we can detect or notice little details
Perceptual Constancy / Perceptual constancies refers to perceiving an object as not changing, or remaining constant even though different images are presented to the retina when the size, shape, or lightness changes or moves
Size constancy / A door that swings open and closed appears to change in size. When the door opens it appears to become slower and larger when the door closes. Size constancy refers to the understanding that regardless of the different images that are produced by it opening and closing, it is still the same door
Shape constancy / A bottle that is turned side ways is going to present a different shape, but most people understand that it is still the same bottle
Lightness constancy / When you wear a yellow sweater outside it will appear brighter than if you wore the same sweater inside. Even though it looks different you know it is still the same sweater
Phi phenomenon- refers to how the movement of fixed lights when presented, or turned on and off could indicate direction, or meaning / Sometimes a restaurant will have a blinking sign out front that appears to have an arrow pointing towards their parking lot. This sign, which appears to show direction, is the result of light blinking on at a certain speed. When the lights start off slow and then speed up it shows a direction as the lights are turned on. Think about dominos- as the dominos fall they fall in a certain direction, which the shows the path that they will fall.

Submitted by Mike McLane, Sterling Heights High School, Michigan: