DO NOW: Which sense would you be most willing to give up? Which one would you least like to lose?

Key Ideas thresholds vision hearing (audition) touch (somatosensation) Chemical senses – taste (gustation) and smell (olfaction) Gestalt organizing principles depth perception perceptual constancy perceptual adaptation and perceptual set ESP

Sensation & Perception How many rectangles do you see???

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Sensation & Perception Sensation: the process by which you detect physical energy from your environment and encode it as neural signals. Perception: the process that organizes sensory input and makes it meaningful. This is influenced by your memory, motivation, emotion, and even culture.

Sensation & Perception Psychophysics: the study of the relationship between physical energy and psychological experiences. Asks questions about our sensitivity to stimuli.

Thresholds stimulus: a change in environment that can be detected by sensory receptors. absolute threshold: the weakest level of a stimulus that can be correctly detected at least half the time (50%).

Thresholds Studied by Galanter about 50 years ago found the following absolute thresholds: a candle flame seen at 30 miles away on a dark clear night the tick of a watch under quiet conditions at 20 feet away 1 teaspoon of sugar in 2 gallons of water 1 drop of perfume diffused in a three-room apartment

Thresholds signal detection theory: minimum threshold changes with fatigue, attention, expectations, motivation, emotional distress, and from one person to another.

Thresholds Subliminal stimulation: receiving messages below one’s absolute threshold for conscious awareness. They can have a momentary, subtle effect on thinking.

Thresholds Difference threshold: minimum difference between any two stimuli that a person can detect 50% of the time. Just noticeable difference (JND): when you experience the difference threshold. e.g. adding one penny to a container with 10 pennies is more noticeable than if it had 100 pennies in it.

Thresholds Weber’s Law: two stimuli must differ by a constant minimum percent (rather than a constant amount). Sensory adaptation: when a stimulus is unchanging, you become less sensitive to the stimulus. Allows you to focus your attention on information changes in your environment without being distracted by irrelevant data such as odors or background noises.

DO NOW In YOUR OWN WORDS, briefly describe the difference between sensation and perception. Then briefly describe absolute and difference thresholds.

Transmission of Sensory Information Sensory information of stimuli comes from millions of sensory receptors in your eyes, ears, nose, tongue, skin, muscles, joints, and tendons. Different receptors detect different types of physical energy.

Transmission of Sensory Information Transduction: transformation of stimulus energy to the electrochemical energy of neural impulses. All this sensory information passes through the thalamus, EXCEPT impulses for olfaction/smell.

Transmission of Sensory Information vision = occipital lobes hearing = temporal lobes smell = lower part of the frontal lobes taste = the junction of the temporal and parietal lobes body senses = parietal lobes

VISION Processed in the primary visual cortex in the occipital lobes. The image formed on your retina is upside down and incomplete. Your brain fills in information and straightens out the upside down image almost immediately.

Visual Pathway cornea: transparent, curved layer in the front of the eye that bends incoming light rays. normal vision: rays of light form a clear image on the retina of the eye.

Visual Pathway nearsighted: too much curvature of the cornea and/or lens focuses the image in front of the retina so nearby objects are seen more clearly than distant objects.

Visual Pathway farsighted: too little curvature of the cornea and/or lens focuses the image behind the retina, so distant objects are seen more clearly than nearby objects.

Visual Pathway Astigmatism: caused by an irregularity in the shape of the cornea and/or the lens. This distorts and blurs the image at the retina.

Visual Pathway iris: colored muscle surrounding the pupil that regulates the size of the pupil opening. pupil: small, adjustable opening in the iris that is smaller in bright light and larger in darkness.

THE EYE

Visual Pathway lens: structure behind the pupil that changes shape, becoming more spherical or flatter to focus incoming rays into an image on the light-sensitive retina. accommodation: process of changing the curvature of the lens to focus incoming rays into an image on the light-sensitive retina.

THE EYE

Visual Pathway dark adaptation: gradual increase in sensitivity to low levels of light when it becomes dark.

Visual Pathway retina: light-sensitive surface in the back of the eye containing rods and cones that transduce light energy. Also has layers of bipolar cells and ganglion cells that transmit visual information to the brain.

DO NOW BRIEFLY define the following parts of the eye: cornea iris pupil lens

THE EYE

Visual Pathway photoreceptors: modified neurons (rods and cones) that convert light energy to electrochemical neural impulses.

Visual Pathway rods: photoreceptors that detect black, white, and gray, and detect movement. Necessary for peripheral and dim-light vision. Distributed throughout the retina, except on the fovea. lower threshold than cones and are sensitive to light and dark, as well as movement.

Visual Pathway cones: photoreceptors that detect color and fine detail in daylight or in bright-light conditions. Most concentrated at the fovea of the retina, none are in the periphery. Three kinds that are each most sensitive to a different range of wavelengths of light, which provides the basis for color vision.

Visual Pathway

fovea: small area of the retina in the most direct line of sight where cones are most concentrated for highest visual acuity in bright light. optic nerve: nerve formed by ganglion cell axons; carries neural impulses from the eye to the thalamus of the brain.

THE EYE

Visual Pathway blind spot: region of the retina where the optic nerve leaves the eye so there are no receptor cells; creates an area with no vision.

Visual Pathway On your post-it note, draw the following image.

Visual Pathway Close your LEFT eye and look at the plus sign. Move the card slowly back and forth until the dot disappears. You have found your blind spot!

DO NOW BRIEFLY define the following parts of the eye: retina rods cones optic nerve

Visual Pathway bipolar cells: second layer of neurons in the retina that transmit impulses from rods and cones to ganglion cells. ganglion cells: third layer of neurons in the retina, whose axons converge to form the optic nerve.

Visual Pathway

acuity: ability to detect fine details, sharpness of vision. Can be affected by small distortions in the shape of the eye. What are some things that we have talked about that effect acuity?

Visual Pathway feature detectors: individual neurons in the primary visual cortex/occipital lobes that respond to specific features of a visual stimulus. e.g. neurons that only respond (fire) to a specific orientation of a line.

Visual Pathway In a study, kittens were raised in three kinds of environments: Vertical stripes Horizontal stripes Normal visual environment

Visual Pathway Kittens raised in an environment with only one line orientation only developed feature detectors for that environment! This means they could only see ONE orientation!

Visual Pathway parallel processing: simultaneously analyzing different elements of sensory information, such as color, brightness, shape, etc.

Color Vision The colors of objects you see depend on the wavelengths of light reflected from those objects to your eyes. Light is the visible portion of the electromagnetic spectrum.

Color Vision

Colors vary in wavelengths from the longest (red) to the shortest (violet). Wavelength is the distance from the top of one wave to the top of the next.

Color Vision Generally, the more lightwaves your eyes receive, the brighter an object appears. If an object absorbs all the lightwaves, none reach your eyes and it appears black. If it reflects all the lightwaves, all of them reach your eyes and it appears white. If it reflects some of the light then we see different colors.

Color Vision trichromatic theory: proposed system of color vision with cones that differentially sensitive to different wavelengths of light. Each color you see results from a specific ratio of activation among the three types of receptors. DEMO

Color Vision opponent-process theory: proposed system for color vision with opposing retinal processes for red-green, yellow- blue, white-black. Some retinal cells are stimulated by one of a pair and inhibited by the other. Spanish castle demo

Color Vision Both seem to be at work to create color vision.

DO NOW: Take out your reading notes. Explain the two major theories of color vision: Trichromatic Opponent-process

Hearing (Audition) audition: the sense of hearing. Sound waves result from mechanical vibration of molecules from a sound source (e.g. instrument or voice). The vibrations move outward from the source, compressing and then releasing the molecules of the air.

Hearing (Audition) amplitude: The height of the sound wave the determines the loudness. The bigger the amplitude, the louder the sound.

Hearing (Audition) frequency: the number of complete wavelengths that pass a point in a given amount of time. The wavelength is inversely proportional to the frequency. It determines the hue of a light wave and the pitch of a sound.

Hearing (Audition) pitch: the highness or lowness of a sound. Shorter wavelength = higher frequency = higher pitch Longer wavelength = lower frequency = lower pitch We are most sensitive to frequencies that correspond to the range of human voices.

Hearing (Audition)

timbre: the quality of a sound determined by the purity of a waveform. What makes a note of the same pitch and loudness sound different on different musical instruments. DEMO

The Ear Outer ear: visible part of the ear; channels the sound waves through the auditory canal to the eardrum. Eardrum: a tight membrane that vibrates with the waves.

The Ear OUTER EAR (pinna) Eardrum outer ear canal

Middle Ear Middle ear: the chamber between the eardrum and cochlea. Hammer, anvil, and stirrup: a piston in the middle ear made up of containing three tiny bones that concentrate the vibrations of the eardrum on the cochlea’s oval window (membrane).

The Ear OUTER EAR (pinna) Eardrum/oval window Hammer anvil stirrup MIDDLE EAR outer ear canal

The Ear Cochlea: a coiled, bony fluid-filled tube in the inner ear through which sound waves trigger nerve impulses.  looks like a snail! The vibrations on the cochlea’s oval window cause vibrations that move the fluid in the tube.

The Ear Basilar membrane: lined with hair cells that are bent by the vibrations from sounds and triggers impulses in the adjacent nerve fibers that converge to form the auditory nerve. The neural messages travel via the thalamus to the temporal lobe’s auditory cortex – and we hear!

DO NOW Briefly explain the process of hearing, from sound waves to transduction (turning them into neural signals).

The Ear Auditory nerve: axons of neurons in the cochlea converge transmitting sound messages through the medulla, pons, and thalamus to the auditory cortex of the temporal lobe. Semicircular canals: three fluid-filled bony channels in the inner ear. They provide information about orientation to the brain to help maintain balance.

OUTER EAR (pinna) Eardrum Hammer anvil stirrup cochlea MIDDLE EAR Basilar membrane (in the cochlea) outer ear canal semicircular canals Eustachian tube auditory nerve INNER EAR

The Ear

Locating Sounds Sound localization: the process by which you determine the location of a sound. With ears on both sides of our head, you can locate a sound source. The side closest to the source of the sound hears it louder.

Locating Sounds Using parallel processing, your brain processes both intensity and timing differences to determine where the sound is. It is hardest to locate a sound directly in front, behind, above, or below you because the sound hits both ears at the same time. Demos

Determining Pitch How can you discriminate small differences in sound frequency or pitch? place theory: the position on the basilar membrane at which waves reach their peak depends on the frequency of a tone.

Determining Pitch Works best with high-pitched sounds. Waves that peak near the close end are perceived as high-pitched. Waves that peak near the far end are interpreted as low-pitched.

Determining Pitch frequency theory: the rate of the neural impulses traveling up the auditory nerve matches the frequency of a tone, enabling you to sense its pitch. Frequency theory explains well how you hear low-pitched tones.

Determining Pitch Individual neurons can only fire at a maximum of 1,000 times per second. A volley mechanism in which cells can alternate firing and achieve a frequency of 4,000 times per second. The brain can read pitch from the frequency of the neural impulses.

Hearing Loss Conduction deafness: loss of hearing that results when the eardrum is punctured or any of the ossicles lose their ability to vibrate. A hearing aid may restore hearing. Nerve (sensorineural) deafness: loss of hearing that results from damage to the cochlea, hair cells, or auditory neurons. Cochlear implants may restore some hearing.

DO NOW Briefly explain one of the theories of pitch detection. Briefly explain how we locate sounds.

TOUCH (SOMATOSENSATION) somatosensation: the skin sensations, or the sense of touch. Made up of four parts: touch/pressure warmth cold pain

TOUCH (SOMATOSENSATION) These parts can combine to create different touch sensations. For example, burning is pain, warmth, and cold. Itching is gentle stimulation of pain receptors.

TOUCH (SOMATOSENSATION) Transduction of mechanical energy happens just below the surface of the skin where neural fibers carry sensory information to your spinal cord. From your spinal cord, the signal crosses in the medulla, to the thalamus, then your somatosensory cortex in your parietal lobes.

TOUCH (SOMATOSENSATION) The amount of somatosensory cortex dedicated in the brain depends on the sensitivity of that area. This has been mapped as the somatosensory map or homunculus.

Hearing Loss

TOUCH (SOMATOSENSATION) Pain follows a slower and less defined pathway, and requires a psychological and physical explanation. gate-control theory: pain is experienced only if the pain messages can pass through a gate in the spinal cord on their route to the brain.

TOUCH (SOMATOSENSATION) The gate is opened by small nerve fibers that carry pain signals, and is kept open by things like anxiety, depression, and focusing on the pain. The gate is closed by neural activity of larger nerve fibers, which conduct most other sensory signals, or by information coming from the brain.

TOUCH (SOMATOSENSATION) Massage, electrical stimulation, acupuncture, ice, and the natural release of endorphins can close the gate. Pain is important because it alert you to injury and often prevents further damage.

BODY SENSES kinesthesis: body sense that provides information about the position and movement of individual parts of your body with receptors in muscles, tendons, and joints. e.g. close your eyes and touch your nose.

BODY SENSES vestibular sense: body sense of equilibrium with hairlike receptors in semicircular canals and vestibular sac in the inner ear.

DO NOW Explain how the sense of touch works. What are the four basic sensations we feel How does pain travel from our elbow to our brain?

CHEMICAL SENSES gustation: the chemical sense of taste with receptor cells in taste buds in fungiform papillae (tissue) on the tongue, on the roof of the mouth, in the throat. There are three kinds of tasters: nontasters, tasters, and supertasters. Molecules must dissolved in saliva or a liquid to be sensed.

CHEMICAL SENSES Five basic taste sensations are: sweet sour salty bitter umami (glutamate)

CHEMICAL SENSES Flavor is the interaction of sensations of taste and odor with contributions by temperature and texture. Babies show a preference for sweet and salty foods, both necessary for survival; and disgust for bitter and sour, which are characteristic of poisonous and spoiled food.

CHEMICAL SENSES The pathway for taste passes to the brainstem, thalamus, and primary gustatory cortex.

CHEMICAL SENSES Olfaction: the chemical sense of smell with receptors in a mucous membrane on the roof of the nasal cavity. Molecules must reach the membrane and dissolve to be sensed. Olfactory receptors synapse immediately with neurons of the olfactory bulbs in the brain with no pathways to the thalamus.

CHEMICAL SENSES Sensory information about smell is transmitted to the hypothalamus and structures in the limbic system associated with memory and emotion, as well as the primary cortex for olfaction on the underside of the frontal lobes.

CHEMICAL SENSES The primary olfactory cortex is necessary for making fine distinctions among odors and using those distinctions to consciously control behavior.

PERCEPTUAL PROCESSES Perception results from the interaction of many neuron systems, each performing a simple task. Natural selection favors a perceptual system that is very efficient at picking up information needed for survival in a 3-D world in which there are predators, prey, competitors, and limited resources.

PERCEPTUAL PROCESSES You brain looks for consistencies and simplicity, making a huge number of perceptual decisions, often without your conscious awareness, in essentially two different ways of processing. The particular stimuli you select to process greatly affect your perceptions.

Attention The set of processes by which you choose from among the various stimuli bombarding your senses at any instant, allowing some to be further processed by your senses and brain. selective attention: focused awareness of only a limited aspect of all you are capable of experiencing.

DO NOW Briefly explain our sense of smell (from when the molecules that create an odor reach your nose).

Gustation Take a small sip of the water in the cup on your table. Does it taste more bitter, sweet, or equally both flavors? Sweet = nontaster Bitter = Supertaster Both = taster

Attention Bottom-up Processing: information processing that begins with sensory receptors and works up to the brain’s integration of sensory information to construct perceptions. It’s data driven. You first sense stimuli, and then process the data to perceive.

Attention For example, Hubel & Weisel’s feature- detector theory assumes that you construct perceptions of stimuli from activity in neurons of the brain that are sensitive to specific features of those stimuli, such as lines, angles, even a letter or face. Hermann von Helmholtz’s constructivist theory maintains that we learn though experience to convert sensations into accurate perceptions.

Attention Anne Treisman’s feature-integration theory proposes that detection of individual features of stimuli and integration into a whole occur sequentially in two different stages. First, detection of features involves bottom-up parallel processing. Second, integration of features involves less automatic, partially top-down serial processing.

Attention Top-down processing: information processing guided by your preexisting knowledge or expectations. It is concept driven. Your expectations, previous experiences, interests, and biases cause different perceptions.

Attention When you perceive a conflict among senses, vision usually dominates, which is called visual capture. This explains why you think the voice is coming from a ventriloquist’s dummy when the puppet’s mouth moves.

Attention

Which half of the woman’s face is in shadow? What instrument is the man playing?

Attention

What rodent do you see? What is the old man wearing on his face?

DO NOW With your table (NOT on paper), briefly explain the difference between top-down and bottom-up processing.

Gestalt Organizing Principles of Form Perception Max Wertherimer, Kurt Koffka, and Wolfgang Kohler studied how the mind organizes sensations into perceptions of meaningful patterns or forms, called a gestalt. They concluded that in perception, the whole is different from, and can be greater than, the sum of its parts. Forms are perceived as a whole.

Gestalt Organizing Principles of Form Perception phi phenomenon: the illusion of movement created by presenting visual stimuli in rapid succession. e.g. movies Demo

Gestalt Organizing Principles of Form Perception Objects are distinct from their surroundings (e.g. figure-ground). visual capture: Gestalt psychologists recognized the importance of figure- ground in perception.

Gestalt Organizing Principles of Form Perception The nervous system is innately predisposed to respond to patterns of stimuli according to rules or principles. e.g. proximity, similarity, continuity, connectedness, closure.

Gestalt Organizing Principles of Form Perception Closure

Gestalt Organizing Principles of Form Perception optical or visual illusions: discrepancies between the appearance of a visual stimulus and its physical reality. Common examples include: reversible figures, illusory contours, the Muller-Lyer illusion, Ponzo illusion, and moon illusion.

Illusory Contours

Muller-Lyer Illusion

Ponzo illusion

moon illusion

Depth Perception the ability to judge the distance of objects. monocular cues: clues about distance based on the image of one eye.

Depth Perception interposition/overlap – when a closer object cuts off the view of part or all of a more distant one.

Depth Perception relative size – the closer of two same-size objects casts a larger image on your retina than the farther one.

Depth Perception

relative clarity – closer objects appear sharper than more distant, hazy objects.

Depth Perception texture gradient – closer objects have a coarser, more distant texture than far away objects that appear more densely packed or smooth.

Depth Perception relative height/elevation – The lowest objects in our field of vision generally seem the closest.

Depth Perception linear perspective – parallel lines seem to converge in the distance.

Depth Perception relative brightness – closer of two identical objects reflects more light to your eyes.

Depth Perception motion parallax – when moving, nearby objects pass quickly while far away objects appear stationary.

Depth Perception accommodation – the flexing and relaxing of our lens.

Depth Perception

binocular cues: clues about distance requiring two eyes. Binocular cues include the more important retinal disparity and convergence.

Depth Perception Retinal disparity: the slightly different view the two eyes have of the same object because the eyes are a few centimeters apart. The degree of retinal disparity decreases with distance. With both eyes open, your brain fuses the two images, resulting in perception of depth.

Depth Perception Convergence: the inward turning of the eyes that occurs when you look at an object that is close to you. The closer the object, the more convergence. It doesn’t work for objects beyond about 8 meters (25 feet).

Perceptual Constancy perceiving an object as unchanging even when the immediate sensation of the object changes.

Perceptual Constancy size constancy: an object appears to stay the same size despite changes in the size of the image it casts on the retina as it moves farther away or closer.

Perceptual Constancy shape constancy: an object appears to maintain its normal shape regardless of the angle from which it is viewed.

Perceptual Constancy brightness constancy: an object maintains a particular level of brightness regardless of the amount of light reflected from it. However, when the context changes, the perceived brightness or color can also change.

Perceptual Constancy The real shape, orientation, size, brightness, and color are perceived as remaining relatively constant even when there are significant variations in the image it projects. Objects can be identified no matter your viewing angle, how far away it is, or how dim the lights are.

Squares A & B are the same color. Discuss with your table WHY we perceive them to be different.

Perceptual Adaptation & Perceptual Set You are able to adapt to changed visual input. e.g. if you where displacement goggles and reach for an object, you will miss at first.

Perceptual Adaptation & Perceptual Set You are able to adapt to changed visual input. e.g. if you where displacement goggles and reach for an object, you will miss at first. Eventually, your vision will correct itself, even if the goggles flip your vision 180º.

Perceptual Adaptation & Perceptual Set Perceptual set: visual perception can also be influenced by cultural factors, assumptions, and beliefs. e.g. For relative size to work, you must be familiar with the object and have been exposed to viewing objects in the distance.

Perceptual Adaptation & Perceptual Set

Culture & Experience Your perceptual set or mental predisposition can influence what you perceive when you look at ambiguous stimuli.

Culture & Experience schemas: concepts or frameworks that organize and interpret information. They form your perceptual set. This can account for people’s interpretations of UFOs, the Loch Ness monster, or seeing a cloud of dust in a movie.

Culture & Experience

1.How many people are in the picture? 2.How many animals? 3.What is the man holding in his hands? 4.What is the woman wearing? 5.Are we looking at a circus or a costume ball?

Extrasensory Perception ESP (extrasensory perception): the controversial claim that perception can occur apart from sensory input.

Extrasensory Perception parapsychology: the study of paranormal events that investigates claims of ESP, including: telepathy: mind-to-mind communication clairvoyance: perception of remote events precognition: perception of future events telekinesis/psychokinesis: moving remote objects through mental processes

Extrasensory Perception In 1998, a National Research Council investigation on ESP concluded that the best available evidence at that time did not support the contention that these phenomena exist.