Sensation and Perception

Sensation The process by which our sensory systems (eyes, ears, and other sensory organs) and nervous system receive stimuli from the environment

Sensation Input comes from the five senses: Visual (Eyes) Audio (Ears) Cutaneous/Tactile (Touch) Olfaction (Smell) (Nose) Gustation (Taste) (Tongue)

Receptor Cells Each of the five senses is specifically coded to only take in one type of stimulus, whether is be light waves, sound waves, smell, taste, or touch.

The process of organizing and interpreting sensory information Perception The process of organizing and interpreting sensory information How we recognize, interpret, and organize our sensations

Bottom-Up Processing Information processing that focuses on the raw material entering through the eyes, ears, and other organs of sensation This is the sensation part of awareness

Top-Down Processing Information processing that focuses on expectations and experiences in interpreting incoming sensory information This is the perception part of your awareness

Top Down Processing can lead to errors!

do you see the tiger. (top down) do you see the hidden tiger do you see the tiger? (top down) do you see the hidden tiger? (bottom up)

do you see the mountains? (top down) do you see the face? (bottom up)

Thresholds Module 9: Sensation

Absolute Threshold A threshold is an edge or a boundary For sensations, it is the point where you either sense a stimulus or don’t Technically, its “The minimum stimulus that a person can detect 50% of the time”

Absolute Detection Threshold The minimum intensity of energy required to produce sensation in a receptor cell Taste: 1 gram of table salt in 500 liters of water

Smell: 1 drop of perfume diffused throughout a three room apartment

Touch:. The wing of a bee falling on your cheek Touch: The wing of a bee falling on your cheek from a height of 1 centimeter Hearing: The tick of a watch from 6 meters away

Vision: A candle flame on a clear night, 30 miles away

One testable way to determine the thresholds for various people is through SIGNAL DETECTION Incremental changes in sound, taste, etc. are made to test for reactions in people. Tone tests (hearing) are an example.

Signal Detection Results Hit signal present and sensed Miss signal present but not sensed False Alarm signal absent, but sensed Correct Rejection signal absent, and not sensed

IE. Frog eye’s have receptor cells that fire only in response to small, dark, moving objects. Theoretically, a frog would starve to death while knee-deep in motionless flies.

Remember……………ABSOLUTE means we either see it, smell it, taste it… Remember……………ABSOLUTE means we either see it, smell it, taste it….or we don’t!

Difference Threshold The minimum difference that a person can detect between two stimuli 50% of the time Also called just noticeable difference (JND) Hey! Is it just me or did suddenly get a little brighter in here?! someone must have turned on another light!

Ernst Weber and Weber’s Law The greater the magnitude of the stimulus, the larger the difference must be in order to be noticed IE. If you are carrying 20 lbs. and add 5 lbs., it’s noticeable. If you are carrying 100 pounds and add 5 pounds, it may not be noticeable. You need to add 10 lbs. to 100 pounds to make it noticeable.

Transduction The process by which a form of physical energy is converted into a coded neural signal that can be processed by the nervous system.

Sensory Adaptation When exposed to a stimuli over a period of time there will be a diminished sensitivity to it If a stimulus is constant and unchanging, eventually a person may fail to respond to it

Example of Sensory Adaptation A hot tub – after a certain period of time no longer seems as hot

Let’s see how good your senses are! TAKE THE AWARENESS TEST ON THE NEXT SLIDE!

Selective Attention Focusing conscious awareness on a particular stimulus (sense) to the exclusion of others The ability to focus on one stimulus at a time Allows a person to function in a world filled with many stimuli

Selective Attention Example Walking down the hallway – all 5 senses are firing. What grabs your attention?

Selective hearing Do you think it exists?

The Visual System: The Structure of the Visual System Module 9: Sensation

Parts of the Eye – Blind Spot

The Structure of the Visual System Cornea Iris Pupil Lens

Retina Light-sensitive surface with cells that convert light energy to nerve impulses At the back of the eyeball

Receptor Cells In sight they change light into neural impulses the brain can understand. Visual system has two types of receptor cells – rods and cones

Rods Visual receptor cells located in the retina Can only detect black and white Respond to less light than do cones

Cones Visual receptor cells located in the retina Can detect sharp images and color Need more light than the rods Many cones are clustered in the fovea. Cones

Fovea The central focal point of the retina The spot where vision is best (most detailed)

Optic Nerve Nerve that carries visual information from the eye to the occipital lobes There are no rods and cones where the nerve exits the eye. So there is a small blind spot in vision.

Retinal Implant

Nearsighted - Myopia

Farsighted - Hyperopia

The Visual System: Color Vision Module 9: Sensation

There are two theories of color vision: Trichromatic Theory Opponent-Process Theory

Can you see what is in the middle?

Trichromatic Theory Young-Helmholtz Theory Cones are pre-set to be sensitive to RED, GREEN, and BLUE. All of the colors that we see are combinations of those three colors.

All other colors can be derived by combining these three. Figure 3.9 from: Kassin, S. (2001). Psychology, third edition. Upper Saddle River, NJ: Prentice Hall. All other colors can be derived by combining these three.

Color Deficient Vision People who lack one of the three types of cones Usually the red or green receptors are missing Usually referred to as color blindness In inherited and found more in males

Red-Green Color Blindness

Opponent-Process Theory Sensory receptors in the retina come in pairs: Red/Green Yellow/Blue Black/White Only one side is “on” at a time

Opponent Process Theory ON” “OFF” red green green red blue yellow yellow blue black white white black

Afterimage Effect

Opponent-Process Theory If one sensor is stimulated, the other is inhibited If one sensor is over-stimulated, and fatigues, the paired sensor will be activated, causing an afterimage

Hearing: The Nature of Sound Module 9: Sensation

Sound Sound, like light, comes in waves Sound is vibration Features of sound include: Pitch Hertz decibels

Pitch A sound’s highness or lowness in tone Dependent on the frequency of the sound wave – the more “waves per second” the higher the frequency or pitch Is measured as hertz (Hz)

Hertz (Hz) A measure of the number of sound wave peaks per second; measures “frequency” Determines the pitch of the sound Human hearing goes from 20 Hz to 20,000 Hz

Low Pitch Wave peaks are far apart Human hearing goes from 20 Hz to 20,000 Hz although some ears (and speakers) are better than others

High Pitch As pitch increases, so do the number of waves Remember - Human hearing goes from 20 Hz to 20,000 Hz note: a kilohertz is 1,000 hertz so 20 kilohertz equals 20,000 hertz

Decibel (dB) A measure of the height of the sound wave Determines the loudness of the sound Sometimes called amplitude

Hearing: The Structure of the Auditory System Module 9: Sensation

Divisions of the Ear

The Structure of the Auditory System Pinna / Auricle Auditory Canal Eardrum Ossicles Hammer, Anvil, Stirrup

Oval Window The point on the cochlea which receives the sound vibration from the ossicles As the oval window vibrates, the fluid in the cochlea vibrates.

The Ossicles amplify the vibration of the eardrum Oval Window The Ossicles amplify the vibration of the eardrum

Cochlea Where sound waves are changed into neural impulses (transduction) A snail shell shaped tube Filled with fluid

Hair Cells The receptor cells for hearing in the cochlea that change sound vibrations into neural impulses Transduction!

Movement of the fluid causes the hair cells to move which causes TRANSDUCTION!

Auditory Nerve The nerve that carries sound information from the ears to the temporal lobes of the brain

EUSTACHIAN TUBE A tube that connects the middle ear to the back of the nose; it equalizes the pressure between the middle ear and the air outside. When you "pop" your ears as you change altitude (going up a mountain or in an airplane), you are equalizing the air pressure in your middle ear.

Semicircular Canals Organs in the inner ear used in sensing body orientation and balance (vestibular sense)

Vestibular Sense Relies on fluid in the semicircular canals of the inner ear Spinning in circles disrupts the fluid.

How do we hear? Place Theory- different frequencies in sound waves cause vibrations at Low Frequencies High Frequencies different places in the cochlea

Frequency Theory- different frequency of the sound wave vibrates the inner ear at a different rate

Hearing: Sound Localization Module 9: Sensation

Localization of Sound Locating where sound is originating from Done through two cues: Which ear hears the sound first? Which ear hears the louder sound?

Localization of Sound

Problems with hearing Conduction deafness (middle ear damage) Nerve deafness (hair cell or auditory nerve damage)

Cochlear Implant

Other Senses: Taste (Gustation) Module 9: Sensation

Taste Taste is a chemical sense. The receptor cells for taste are the taste buds.

Taste Taste is a chemical sense. The little bumps on our tongues are actually called papillae Inside some of these papillae are clumps of taste cells. These clumps of cells are actually the taste buds.

Taste On average, adults have about 7,500 taste buds. These receptor cells are located in the tongue and in the mouth. When food dissolves on these receptors, TRANSDUCTION occurs Damaged taste receptor cells are replaced within a few days to 2 weeks

Taste Sensations sweet sour salty bitter - umami (savory-msg)

Supertasters People with an abundance of taste receptors Approximately 25% of the population

Nontasters People with a minimum of taste receptors Taste with less intensity than the rest of the population Approximately 25% of the population

Other Senses: Module 9: Sensation

Smell Smell is a chemical sense. Olfactory receptors/cells in the upper nasal passages detect molecules in the air. Taste and smell interact to produce flavor.

Other Senses: Touch

Touch Touch receptors are on the skin Four basic skin senses are Pain warmth cold pressure All skin sensations are a combination of these four basic senses

Sensitivity of Diff body to pain Most Sensitive Back of knees Neck region Bend of elbow Least Sensitive Tip of the Nose Sole of foot Ball of thumb

Pain messages travel on one set of nerve fibers containing pain gates. The gates are open when pain is felt. Other sensory messages go through another set of fibers. The non-pain fibers can close the pain gates to stop the sense of pain.

Suppressing Pain (this is a link…in case its not working….)

Other Sense: Body Senses Module 9: Sensation

Kinesthetic Sense The system for sensing the position and movement of individual body parts Relies on receptor cells from the muscles and joints One’s leg “falling asleep” is a disruption of the kinesthetic sense

The End