Sensation and Perception

Sensation and Perception Chapter 3

The Nature of Sensation Section 1

Sensation: smells, sights, sounds, taste, balance, touch, and pain • Experience of sensory stimulation • Perception: mental process of soring, identifying, and arranging the bits into meaningful patterns • Process of creating meaningful patterns form raw sensory information

The Basic Process • Sequence of events that produces a sensation • Step 1: there needs to be some form of energy that stimulates a receptor cell—a specialized cell that responds to a particular type of energy—in one of the sense organs • Ex: light waves or vibrations to the eye or ear • Step 2: if the stimulus is strong enough the receptor sends a signal to the appropriate part of the brain • Step 3: Sense what is around us • Ex: Seeing or hearing

How does the brain distinguish between sights and sounds, sensations of touch and balance? • Sensory Discrimination • Begins in with receptor cells that are connected to specialized neural pathways • Sensory messages enter the brain on different channels • EX: bright lights sends a more rapid firing neuronand dim lights have a less rapid firing neuron

Sensory Threshold • The energy reaching a receptor must be intense enough to have a noticeable effect • Absolute Threshold: the minimum intensity of physical energy requited to produce any sensation

Under ideal conditions… • Taste: 1 gram of salt in 500 liters of water • Smell: 1 drop of perfume in a 3 room apartment • Touch: the wing of a bee falling on your cheek form 1 cm of height • Hearing: the tick of a watch 20 feet away in very quite conditions • Vision: a candle flame seen from 30 miles away on a clear dark night

Absolute Thresholds vary depending on the level and nature of on going sensory stimulation • Ex: when you walk into a dark movie theater you cant seen anything other than the screen until your eyes gradually adjust when your eyes come accustom to the darkness • Sensory Adaptation: an adjustment of the senses to the level of stimulation they are receiving

With our senses what we notice most is the change…change form no stimulation to stimulation or less to more • Difference Threshold or Just noticeable Difference: the smallest change in a stimulation that can be detected 50% of the time • Varies from person to person • Ernest Weber • Weber’s Law: principle that the Just Noticeable Difference for any give sense if constant fraction or proportion of the stimulus being judged • Ex: Hearing is very sensitive and an detect a change in sound that is 1/3 of 1%

Subliminal Perceptions • Story goes…. • 1950’s a movie theater in Fort Lee, NJ added messages like “drink coke” and “eat popcorn” between frames of the movie Panic • Although the messages where flashed to quickly for the moviegoers to notice them consciously • Legend has it that soda and popcorn sales increased dramatically

In actuality… • There was no change in sale • According to a survey nearly 2/3 of Americans believe hat advertisers put hidden messages and images in their advertisements to increase sales of their products • Can people influence by information of which they are not consciously aware? • YES! • Ex: experimental group was exposed to competition and the control group was exposed to a list of neutral words • Words were flashed on a screen too rapidly for participants to identify them • Late all participants played a game and the experimental group was particularly Competitive

Does not mean that people automatically or mindlessly “obey” subliminal messages • The exact opposite seems to be true—in independent scientific studies it has been shown that hidden messages outside the laboratory have no significant affect on behavior • But the mind can play trick on itself… another studies showed that a group of volunteers listened to memory improvement tapes • Half of them said it worked on them and they were remembering more but • They were actually listening to self improvement tapes

Extra Sensory Perception • People claim to have extra power of perception know as Extra Sensory Perception or ESP • Refers to a variety of phenomena including • Clairvoyance: awareness of an unknown object or event • Telepathy: knowledge of someone else's thoughts or feelings • Ex: reading someone's mind • Precognition: foreknowledge of future events • Ex: seeing into the future

Parapsychology: the study of the operation of ESP and other psychic phenomena • Much of the research into ESP has been criticized for… • poor experimental design • failure to control for dishonesty • selective reporting of results • inability to obtain replicable results • Not all psychologists discount ESP, 34% of all psychologists accept ESP as either an established fact or a likely possibility

Vision Section 2

The Visual System • How we see • Light enters through the cornea—the transparent protective coating over the front part of the eye • It then passes though the pupil—a small opening in the iris which light enters the eye

Iris: the colored part of the eye • In very bright light the iris contract to make the pupil smaller to protect the eye and make us see better in bright lights • In dim light it widens and lets in as much light as possible to see best

Inside the pupil, light moves through the lens—transparent part of the eye inside the pupil that focuses light into the retina • Retina: lining of the eye containing receptor cells that are sensitive to light

The lens changes shape to focus on objects that are closer and farther away • Normally, the lens is focuses on the middle • Blind spot: the place on the retina where the axons of all the ganglion cells leave the eye and where there are no receptors

On the retina directly behind the lens, lies a depressed spot called the Fovea • Occupies the center of visual field, and images are the sharpest in focus here • When we want to examine something in fine detail, we bring it close to the fovea

Receptor Cells • Each retina contains a receptor cell responsible for vision • Theses cells are only sensitive to a fraction of the spectrum of electromagnetic energy • Includes light—the segment of the electromagnetic spectrum we can see • 2 kinds of receptor cells—rods and cones • Rods: receptor responsible for night vision and perception of brightness • Cones: receptor responsible for color vision

Rods and cones connect to specialized neurons called bipolar cells • Neurons with only one axon and one dendrite • The one –to-one connection between cones and bipolar cells allows for maximum visual acuity • Visual Acuity: ability to distinguish fine details visually

Adaptation • The process by which our sense adjust to different levels of stimulation • Dark Adaptation: increased sensitivity of the cones and rods in darkness • Ex: After sitting in the dark taking notes and the lights are turned on your eyes are sore and sensitive to light • Light Adaptation: decreased sensitivity of rod and cones in bright light • EX: When you are outside all day in bright light and it does not affect you

Afterimage • Sense experience that occurs after the visual stimulus is removed • Afterimage Test • Stare continuously, without blinking at the yellow dot on the left image for 20 seconds • Then look at the white square to the right • What do you see?

From eye to brain • We don’t actually “see” with our eyes but instead with our brains • Messages from the eye must make there way to the brain for sight to occur • The rods and cones are connected to bipolar cells in many different numbers and combinations • The bipolar cells then hook up with ganglion cells—neurons that connect the bipolar cells in the eye to the brain • The axons of the ganglion cells join together to form the optic nerve—bundle of axons of ganglions that carries neural messages form eye to brain

After they leave the eye, these fibers that make up the optic nerves, separate and some cross to the other side of the bead at the optic chiasm • Optic Chiasm: point near the base of the brain where some fibers in the optic nerve from each eye cross to the other side of the brain • What we see with our right eye is processed to our left occipital lobe and what we see with our left eye is processed in the right occipital lobe • See page 107 of textbook

Color Vision • Properties of Color • Psychologists call different colors hues and what hues you see depends on the wave length of light reaching your eyes • The vividness or richness of a hue is called saturation • Brightness: the nearness of a color to white opposed to black • Hue, saturation, and brightness are 3 separate aspects of our experience of color • Most people can identify 150 distinct hues but graduations of saturations and brightness allows us to see many variations of that hue

Theories of Color Vision • There are only 3 colors—red, yellow and blue • Hermann von Helmholtz and the Trichromatic Theory • Proposed a theory of color vision based on Additive Color Mixing—mixing lights of different wavelengths to create new hues • His explanation for color vision is know as Trichromatic Theory (3 color theory) • The theory of color vision that hold that all color perception derives from 3 different color receptors in the retina • Usually red, green and blue receptors

Also explains how 3 primary colors can be combined to make other hues and accounts for people with color blindness • Trichromats: people who have normal color vision • Color Blind: partial or total inability to perceive hues • 10% of men and 1% of women • Dichromats: people who are blond to either red-green or yellow blue

Monochromts: people who are totally color blind and only see in shades of light and dark • Extremely rare • Edward Hering and the Opponent Process Theory • Alternate theory of color vision that helps to explain monochromats • 3 pairs of colors yellow-blue, red-green, and black-white • Yellow- blue and red-green determine the hue you see and black-white determines the brightness of the color • We can either see something that is yellow or blue but not yellowish blue • Also explains afterimages

Color Vision in other Species • Many animals have color vision, but the colors they see varies • Humans and most primates are trichromats and most other mammals are dichromats • Hamsters, rats, squirrels, and other rodents are completely color blind, or monochromats • Some animals see colors we cannot see • Ex: Bees see Ultraviolet light • Bees see flowers with white petals that look drab to us as flash to them like neon signs

Hearing Section 3

Sound • Sound: our brain’s interpretation of the flow of air molecules pounding against our eardrum • Sound Waves: how sound travels • Frequency: how often a wave occurs • Hertz: the unit of measurement for wave cycles • Pitch: how high or low a sound is • Amplitude: the height of a wave • Along with frequency determines how loud a sound is • Measured in decibels

80+ Decibels potential ear damage • Concerts, lawnmower, subway train, headphones at full volume • 130+ pain threshold • Revolver firing a close rang

The Ear • Hearing begins when sound waves strike the eardrum and cause it to vibrate • The vibration causes 3 tiny bones in the middle ear to hit each other in sequence and thus carry vibrations to the inner ear • Hammer, anvil and stirrup

The stirrup (last bone) is attached to the Oval Window—membrane across the opening between the middle and inner ear that conducts vibrations to the cochlea • Cochlea: part of the inner ear containing fluid that vibrates, which in turn causes the basilar membrane to vibrate—snail shaped

The cochlea is divided lengthwise by the basilar membrane—vibrating membrane in the cochlea of the inner ear; it contains sense receptors for sound • Lying on top of the basilar membrane, and moving in sync with it is the organ of Corti—contains the receptor cells for hearing • Thousands of tiny hair cells • The brain pools the information from thousands of these cells to perceive sounds

Neural Connections • Each ear sends messages to both cerebral hemispheres • The primary destination for the auditory messages are the temporal lobes

Theories in Hearing • The more neurons activated, or fired the louder the sound • 2 basic theories for pitch—place theory and frequency theory • Place Theory: pitch is determined by the location of greatest vibration on the basilar membrane • High frequency/ pitch sounds are at the base • Low frequency/ pitch sounds are at the opposite end

Frequency Theory: pitch is determined by the frequency with which the hairs in the cochlea fire • If the hair bundle is pulled or pushed rapidly it is a higher frequency/ pitch sound • Volley Principle: Auditory neurons fire in sequence: one neuron fires and then the next and so on. By then the first one has time to recover and can fire again • Send a more rapid series of impulses than just one neuron

Hearing Disorders • Estimated 28 million Americans suffer from partial or total deafness • Injury, infections, explosions and long term exposure to loud noise can harm your hearing and cause partial to total deafness • 30 million people are exposed to damaging noise levels daily • Ex: leaf blowers, chainsaws, jet planes, headphones and personal stereos • People 45-65 are more likely to experience natural hearing problems • Most cases of deafness in old age is result of undetected ear infections in childhood, exposure to noise

People with irreversible damage can use devices to increase their hearing • Hearing aids • Cochlear implants can help people with total deafness due to cochlear damage

Exit Slip: Your Hearing Ability • Test 1: How old are your ears? • After listening to the recording write down how old your ears are. • Test 2: Basic Hearing Test • Listen for the first tone you can hear and write down what the screen says about your hearing. • Question 1: Do you think you have good hearing? • Question 2: Do you think you are contributing to your hearing impairments?

The other Senses Section 4

Smell • Smell is the most primitive • We feel that most smells are either alluring or repulsive…we rarely think of a smell as neutral • We either like it or not • A mere whiff can trigger sudden, unexpected, emotionally charged memories • Romance, childhood memory, special memory etc. • Smells evoke powerful memories because some of the nerves in our nose are directly connected to parts of the brain that are responsible for emotion and memory

Many use odors to distinguish between good and bad, safe and unsafe • Ex: smell of smoke and fire, sour milk and being expired • Smell undergoes adaptation that why you may not smell the perfume/cologne you sprayed hours ago when other still can • Detecting Common Odors • Sense of smell is activated by complex protein produced in a nasal gland • As we breathe a fine mist of protein called Odorant Binding Protein (OBP) is sprayed through the tip of the nose

The protein combines with airborne molecules that activate receptors located high in each nasal cavity in a patch of tissue called the Olfactory Epithelium—nasal membranes containing receptor cells sensitive to odors. • The axons from these million receptors go directly to the Olfactory blub—smell center of the brain • From there it is routed to the temporal lobes resulting in awareness of the sent

Communicating with Pheromones • Many animals use chemicals as means of communication • Invisible, sometimes, odorless molecules called Pheromones secreted by glands or in urine can have powerful effects on animal behavior • Pheromones stimulate receptors in the Vomeronasal Organ—location for the pheromones in the roof of the nasal cavity • Sends messages to a second olfactory bulb specially designed to interpret pheromonal communications

Pheromones also provide information about another animal’s identity • When an animal sniffs another member of their species they can identify the last time the animal ate, how dominate they are, if they are healthy, and their gender

Sensation and Perception