UNIT 4 Sensing the World: Some Basic Principles Vision Hearing Other Senses Perceptual Organization Perceptual Interpretation Is there Extrasensory Perception? Gestalt Principles Perceptual Constancies Visual Illusions Basic Principles Depth Perception Perception Sensation Vision Theories The Eye Touch/Pain Other Senses Taste We are here Hearing The Ear Smell Theories How do we construct our representations of the external world? To represent the world, we must detect physical energy (a stimulus) from the environment and convert it into neural signals. This is a process called sensation. When we give meaning by selecting, organizing, and interpreting our sensations, the process is called perception. Sensation receptors detect information Perception organization and interpretation of sensory information The process of creating meaningful patterns from raw sensory information One continuous process… Bottom-up processing Top-down processing Perception Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind. Letter “A” is really a black blotch broken down into features by the brain that we perceive as an “A.” CONSTRUCT A WHOLE FROM ITS PARTS Information processing is guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations. THE CHT CONCEPTUALLY DRIVEN, CONSTRUCTED ON EXPECTATIONS Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a total mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. Selective attention Cocktail party effect Cell phone use and car accidents Inattentional blindness Video examples http://www.youtube.com/watch?v=IGQmd oK_ZfY Change blindness http://www.wimp.com/personswapping/ http://www.youtube.com/watch?v=ElLnNalL4xY Change deafness Choice blindness http://www.youtube.com/watch?v=wRqyw- EwgTk&noredirect=1 Choice blindness – blindness Psychophysics Smallest detectable LEVEL of a stimulus. Absolute Threshold Intensity No No No Yes Observer’s Response Detected Tell when you (the observer) detect the light. Yes Taste: 1 gram (.0356 ounce) of table salt in 500 liters (529 quarts) of water Smell: 1 drop of perfume diffused throughout a three-room apartment Touch: the wing of a bee falling on your cheek from a height of 1cm (.39 inch) Hearing: the tick of a watch from 6 meters (20 feet) in very quiet conditions Vision: a candle flame seen from 50km (30 miles) on a clear, dark night Predicts how and when we detect the presence of a faint stimulus (signal) amid background noise (other stimulation). SDT assumes that there is no single absolute threshold and detection depends on: Person’s experience Expectations Motivation Level of fatigue Subliminal (below threshold) Priming Subliminal persuasion Difference threshold Just noticeable difference (jnd) Weber’s Law STIMULUS CONSTANT (k) Light 8% Weight 2% Tone 3% The smallest detectable CHANGE in a stimulus Also called the just noticeable difference (jnd) Difference Threshold: Minimum difference between two stimuli required for detection 50% of the time, also called just noticeable difference (JND). Difference Threshold No No Yes Observer’s Response Tell when you (observer) detect a difference in the light. Two stimuli must differ by a constant minimum percentage (rather than a constant amount), to be perceived as different. Weber fraction: k = dI/I. Light Constant (k) 8% Weight 2% Tone 3% Stimulus Weber’s Law States that the difference threshold is a constant proportion of the specific stimulus Senses vary in their sensitivity to changes in stimulation More than just sensation it has to do with sales. Who will notice if we add 2 lbs? Diminishing sensitivity to an unchanging stimulus After constant exposure to a stimulus, our nerve cells fire less frequently An adjustment of the senses to the level of stimulation they are receiving Ever forgotten you are wearing a watch? Ever gotten used to a smell? Then why don’t things disappear from your vision? Gestalt Principles Perceptual Constancies Visual Illusions We are here Depth Perception Perception Sensation Vision Theories Basic Principles The Eye Touch/Pain Other Senses Taste Hearing The Ear Smell Theories Waves of electromagnetic energy Hits an object Some is absorbed Some is reflected (the color you see) sensory info (e.g. sound waves, light waves, etc.) converted to a format the CNS can use… an ACTION POTENTIAL. Unique transducers for each sense/organ Organ Sense Receptors Transduce… Eyes Light waves Ears Sound waves Tongue Flavor molecules Nose Scent molecules Skin Pressure energy Brightness: Hue: Gestalt Principles Perceptual Constancies Visual Illusions Basic Principles Depth Perception Perception Sensation Vision Theories The Eye We are here Touch/Pain Other Senses Taste Hearing The Ear Smell Theories Cornea Pupil Iris Lens Accommodation Retina Cornea = outer covering of the eye. Pupil = the adjustable opening in the center of the eye through which light enters. 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. The iris dilates/constricts in response to changing light intensity Lens = the transparent structure behind the pupil that changes shape to help focus images on the retina. Retina = the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information. Rods and cones Cones Rods Rods: • Enable light/motion detection • Share bipolar cells with other rods (send combined messages) • Remain sensitive in dim light Cones: • Cluster in and around the fovea • Direct hotline to the brain – preserves precise information (better able to detect fine detail) • Enable color vision • only in bright light, in dim light color vision is lost Optic nerve Blind spot fovea Blind Spot = the point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there. Fovea = the central focal point in the retina, around which the eye’s cones cluster. Optic Nerve = the nerve that carries neural impulses from the eye to the brain. https://www.youtube.com/watch?v=cFVbLnX Wn6A Sclera: White Iris: Colored. Controls size of pupil. Pupil: Black. Hole. Light enters, hits lens. Cornea: Covering. Bends light. Lens: Light hits here. Shifts shape to focus light. Retina: Membrane at back of eye. “Movie screen.” Where light becomes neural activity. Fovea: Sharpness. Contains cones. Color. Rods: Shapes Cones: Color Ganglion Cells: Connects retina to brain. Optic Nerve: Axons of ganglia, project to brain. Gestalt Principles Perceptual Constancies Visual Illusions Basic Principles Depth Perception Perception Sensation Vision Theories The Eye Other Senses Hearing The Ear We are here Touch/Pain Taste Smell Theories Our brain’s perceptual system compensates for missing information. Different parts of the cortex detect different components of vision (shape, edges, motion, color). Use minimal patterns to identify objects Ex: See edges of this object… identify it as a chair An important aspect of social function!! Feature detectors Parallel processing Blind sight Young-Helmholtz trichromatic (three color) theory Red Green Blue Monochromatic Dichromatic Opponent-process theory Three sets of colors ▪ Red / Green ▪ Yellow / Purple ▪ Blue / Orange Afterimage Gestalt Principles Perceptual Constancies Visual Illusions Basic Principles Perception We are here Sensation Vision Theories Depth Perception The Eye Touch/Pain Other Senses Taste Hearing The Ear Smell Theories Audition Amplitude Loudness Frequency Pitch Amplitude loudness Frequency pitch Gestalt Principles Perceptual Constancies Visual Illusions Basic Principles Depth Perception Perception Sensation Vision Theories The Eye Touch/Pain Other Senses Taste We are here The Ear Smell Hearing Theories Outer ear Auditory canal Ear drum The ear is divided into the outer, middle and inner ear. The sound waves travel down the auditory canal to the eardrum. Eardrum = tight membrane that vibrates when struck by sound waves. Eardrum Middle ear Hammer, anvil, stirrup Bones of the middle ear = the hammer, anvil, stirrup which vibrate with the eardrum. Hammer Anvil Stirrup Oval window = where the stirrup connects to the cochlea. Cochlea = a coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses. Inner ear Oval window Cochlea Basilar membrane Auditory nerve Auditory cortex Oval Window Cochlea Fluid in the cochlea Hair cells in the cochlea Auditory nerve = nerve which sends the auditory message to the brain via the thalamus. Nerve fibers Auditory nerve Gestalt Principles Perceptual Constancies Visual Illusions Basic Principles Depth Perception Perception Sensation Vision Theories The Eye Other Senses Hearing The Ear Theories We are here Touch/Pain Taste Smell Basilar membrane's hair cell Compressed sound Place Theory and Frequency Theory Place theory High pitched sounds Frequency theory Low pitched sounds Volley principle Stereophonic hearing Localization of sounds Intensity Speed of sound NERVE (SENSORINEURAL) DEAFNESS CONDUCTION DEAFNESS Something goes wrong with the sound and the vibration on the way to the cochlea. You can replace the bones or get a hearing aid to help. The hair cells in the cochlea get damaged. Loud noises can cause this type of deafness. NO WAY to replace the hairs. Cochlea implant is possible. Cochlear implants are electronic devices that enable the brain to hear sounds. Cochlear Implant Gestalt Principles Perceptual Constancies Visual Illusions Basic Principles Depth Perception Perception Sensation Vision Theories We are here The Eye Touch/Pain Other Senses Taste Hearing The Ear Smell Theories Skin is the largest sense organ There are receptors for pressure, temperature, and pain Touch appears to be important not just as a source of information, but as a way to bond with others Touch Localization Touch localization depends on the relative lengths of the pathways from the stimulated parts to the brain. Types of touch Pressure Warmth Cold Pain Sensation of hot Hairy/Glabrous skin Rubber hand illusion https://www.youtube.com/watch?v=XEayC_fXGYY&index=2&list=PLcrwo6ba 3he9q8BG9GcFy17Ysi_XoeICe Kinesthesis Vestibular sense Semicircular canal Vestibular Sacs Biological pain Nociceptors Endorphins Phantom limb sensations Spinal cord contains small nerve fibers that conduct most pain signals It also contains larger fibers that conduct most other sensory signals When tissue is injured small nerve fibers activate and open the neural gate BUT… Large fiber activity shuts that gate Thus if you stimulate gate closing activity by massage electrical signal or acupuncture you can disrupt the pain message. The brain can close this gate too! Pain tells the body that something has gone wrong. Usually pain results from damage to the skin and other tissues. A rare disease (CIPA) exists in which the afflicted person feels no pain. AP Photo/ Stephen Morton Ashley Blocker (right) feels neither pain nor extreme hot or cold. Psychological influences Rubber-hand illusion (mirror neurons) Memories of pain Social-cultural influences Physical methods Psychological methods Gestalt Principles Perceptual Constancies Visual Illusions Basic Principles Depth Perception Perception Sensation Vision Theories The Eye Touch/Pain Other Senses Taste We are here Hearing The Ear Smell Theories Four basic tastes Sweet Salty Sour Bitter Recent discovery of fifth taste Umami – Japanese word meaning pleasant savory taste. People taste umami through receptors for glutamate, commonly found in its salt form as the food additive monosodium glutamate (MSG) Taste buds Little bumps on top and sides of tongue Taste receptor cells inside taste bud pores Chemical sense Age and taste As we age, number and sensitivity of taste buds decreases Sensory interaction Interaction of smell and taste McGurk Effect Interaction of other senses https://www.youtube.com/watch?v=RbNbE4egj_A Like taste, smell is a chemical sense. Odorants enter the nasal cavity to stimulate 5 million receptors to sense smell. Olfaction Chemical sense Odor molecules Olfactory bulb Olfactory nerve Ability to identify smell peaks during early adulthood, but steadily declines after that. Women are better at detecting odors than men. The brain region for smell (in red) is hard wired into brain regions involved with memory (limbic system – amygdala and the hippocampus). That is why strong memories are made through the sense of smell. The extraordinary sensory condition in which stimulation of one modality leads to perceptual experience in another. Literally, the term means “to perceive together.” typographic synesthesia Gestalt Principles Perceptual Constancies We are here Visual Illusions Basic Principles Depth Perception Perception Sensation Vision Theories The Eye Touch/Pain Other Senses Taste Hearing The Ear Smell Theories Visual Illusions We are here Gestalt Principles Perceptual Constancies Basic Principles Depth Perception Perception Sensation Vision Theories The Eye Touch/Pain Other Senses Taste Hearing The Ear Smell Theories We organize the sensory information coming into our brains. We make assumptions about the sensory information. Oftentimes our perception is greater than the sum of the parts actually presented to our senses. From the German word meaning ‘the whole’ Studied human perceptual self-organizing tendencies. Found that the brain creates a coherent perceptual experience that is more than simply the sum of the available sensory information AND it does this in predictable ways So predictable that artists can exploit our common perceptions to do things like 3D art Determine Figure from the background (figure-ground) We organize the visual field into objects (figures) that stand out from their surroundings (ground). What you make the figure and what you back the background determines your perception And finally………. The WHOLE family! Mother, Father and daughter!!! Can you find nine people in this picture? Grouping Proximity Similarity Continuity Connectedness Closure Grouping Proximity Closure Similarity Continuity Connectedness https://www.youtube.com/watch?v= mf5otGNbkuc Proximity Closure Similarity Continuity connectedness The Principle of Common Region states that objects that are within the same region are perceptually grouped together. Depth perception enables us to judge distances. Gibson and Walk (1960) suggested that human infants (crawling age) have depth perception. Even newborn animals show depth perception. https://www.youtube.com/watch?v=p6cqNhHrMJA Visual Cliff Binocular cues Depth perception that we have because we have TWO eyes Retinal disparity: Images from the two eyes differ. While focusing far away try touching your fingers about 5 inches directly in front of your eyes. You will see a “finger sausage” The amount of disparity (difference) between the two images can be used as a cue for distance Try holding up two fingers one in front of the other. Focus on the front one (you should now see two images of the back one). Now move the back one away from, then back towards you, while still focusing on the front one. Convergence: Neuromuscular cues. When two eyes move inward (towards the nose) to see near objects and outward (away from the nose) to see faraway objects. Monocular cues Horizontal-vertical illusion Monocular cues Relative height Relative size Interposition Linear perspective Relative motion Light and shadow Relative Height: We perceive objects higher in our field of vision as farther away Relative Size: If two objects are similar in size, we perceive the one that casts a smaller retinal image to be farther away. Interposition: Objects that occlude (block) other objects tend to be perceived as closer. Linear Perspective: Parallel lines, such as railroad tracks, appear to converge in the distance. The more the lines converge, the greater their perceived distance. Relative motion: Objects closer to a fixation point move faster and in opposing direction to those objects that are farther away from a fixation point, moving slower and in the same direction. Light and Shadow: Nearby objects reflect more light into our eyes than more distant objects. Given two identical objects, the ones that are shaded on top are seen as “sticking out toward us” Stroboscopic motion: Created by a rapid series of still pictures https://www.youtube.com/watch?v=xSrDnIVg Vv0 Phi phenomenon: Apparent motion created by lights flashing in sequence Perceptual constancy – ability to recognize objects without being deceived by changes in their shape, size, brightness or color even as illumination and retinal images change Shape Constancy: we perceive the form of familiar objects as remaining the same even if projected retinal image changes Size constancy: we perceive objects as having a constant size, even if projected image appears to change sizes Ponzo illusion Moon illusion Lightness/brightness constancy: we perceive an object as having a constant lightness even when its illumination varies Relative luminance: amount of light an object reflects is relative to its surroundings Color constancy: we perceive familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object Surrounding context Surrounding objects Experiments on sensory deprivation Critical period Perceptual adaptation Displacement goggles https://www.youtube.com/watch?v=eA2d1tKNFoU Perceptual set: a bias or readiness to perceive certain aspects of available sensory data and to ignore others Schemas: used to organize and interpret unfamiliar information http://jeffmilner.com/backmasking/ Context effects “eel” on the wagon vs “eel” on the orange morning vs mourning Motivation on perception Emotion on perception Parapsychology Extrasensory perception Clairvoyance – awareness of an unknown object or event Telepathy – knowledge of someone else’s thoughts or feelings Precognition – foreknowledge of future events Psychokinesis –movement of physical objects by the mind without the use of physical means Psychic predictions Nostradamus ESP experiments
