Sensation and Perception

Sensation & PerceptionPART II : Sensation & PerceptionPART II AP PSYCHOLOGY

Perceptual Organization: Gestalt : Perceptual Organization: Gestalt Grouping the perceptual tendency to organize stimuli into coherent groups Grouping Principles proximity--group nearby figures together similarity--group figures that are similar continuity--perceive continuous patterns closure--fill in gaps connectedness--spots, lines, and areas are seen as unit when connected simplicity– sets that are alike

Perceptual Organization: Grouping Principles : Perceptual Organization: Grouping Principles

Law of Proximity : Law of Proximity We group nearby figures together. We don’t see 6 separate lines, but three sets of two lines.

Slide 5 : Law of Proximity

Law of Similarity : Law of Similarity We group figures that are similar together. We see the triangles and circles as vertical columns of similar shapes, not as horizontal rows of dissimilar shapes.

Slide 7 : The Law of Similarity

Law of Continuity : Law of Continuity We perceive smooth, continuous patterns rather than discontinuous ones. This pattern could be a series of alternating semicircles, but we perceive it as two continuous lines- one wavy, one straight.

Slide 9 : The Law of Continuation

Law of CLOSURE : Law of CLOSURE We fill in the gaps to create a complete, whole object. We assume that the circles near the right are completed but partially blocked by the illusionary triangles. Add a few line segments that close off the circles and your brain stops constructing a triangle.

Law of Closure : Law of Closure Gestalt grouping principles are at work here.

Distal and Proximal Stimuli : Distal and Proximal Stimuli How do we perceive the world? Distally The world outside of the body Things your physical eyes cannot touch (you can see only) Proximally Stimulus energies that touch your sensory receptors inside the body Light that falls on retina is proximal

Slide 13 : Proximal stimuli is distorted. Objects you perceive (distal) are different than the stimulus energies (proximal) that represent them. Example A square piece of paper on a desk Move it away and the shape seems to change Paper- distal stimulus Image projected on your retina- proximal stimulus

PERCEPTUAL HYPOTHESIS : PERCEPTUAL HYPOTHESIS A guess about which distal stimuli is responsible for the proximal stimuli sensed. Educated guesses that your perceptual system makes about stimuli representation distally and proximally

Perceiving Depth and Distance : Perceiving Depth and Distance Depth Perception Interpretation of visual cues that indicate how near or far away objects are. 2 Types of cues to perceive distance Binocular depth cues Clues about distance based on the differing views of the two eyes. Monocular depth cues Clues about distance based on the image in either eye alone Depth Perception ability to see objects in three dimensions allows us to judge distance

Depth Perception: Binocular cues(based differing views of the two eyes) : Depth Perception: Binocular cues(based differing views of the two eyes) Retinal Disparity images from the two eyes differ closer the object, the larger the disparity Convergence neuromuscular cue two eyes move inward for near objects

Perceptual Organization: Depth Perception : Perceptual Organization: Depth Perception Visual Cliff – a laboratory device for testing depth perception in infants and young animals. It suggests that the ability to perceive depth is at least partially innate.

Perceptual Organization: Depth Perception : Perceptual Organization: Depth Perception Visual Cliff

Perceptual Organization: Depth Perception : Perceptual Organization: Depth Perception Illusory Depth

Perceptual Organization: Depth Perception : Perceptual Organization: Depth Perception Illusory Depth Explanation

Perceptual Organization: Size-Distance Relationship : Perceptual Organization: Size-Distance Relationship The Ames Room

Perceptual Organization: Monocular Cues(based on image in either eye alone) : Perceptual Organization: Monocular Cues(based on image in either eye alone) 2 Kinds of Monocular Depth Cues Motion Parallax Objects at different distances move across the retina at different rates Pictorial Cues Clues about distance that can be given a flat picture There are six pictorial cues

Perceptual Organization: Depth Perception : Perceptual Organization: Depth Perception Monocular Cues relative size smaller image is more distant interposition closer object blocks distant object relative clarity hazy object seen as more distant texture coarse --> close fine --> distant

Perceptual Organization: Depth Perception : Perceptual Organization: Depth Perception Relative Size

Perceptual Organization: Depth Perception : Perceptual Organization: Depth Perception Interposition

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Perceptual Illusions : Perceptual Illusions

Perceptual Illusions : Perceptual Illusions

Perceptual Organization: Depth Perception : Perceptual Organization: Depth Perception Monocular Cues (cont.) relative height higher objects seen as more distant relative motion closer objects seem to move faster linear perspective parallel lines converge with distance relative brightness closer objects appear brighter

Perceptual Organization: Depth Perception : Perceptual Organization: Depth Perception Relative Height

Relative Motion : Relative Motion

Perceptual Organization: Depth Perception : Perceptual Organization: Depth Perception Perspective Techniques

Slide 34 : Linear Perspective

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Perceptual Organization: Depth Perception : Perceptual Organization: Depth Perception Light and Shadow

In or Out? : In or Out?

Perceiving Geographical Slant : Perceiving Geographical Slant Steepness of hill judgments People tend to overestimate steepness Study done on this phenomenon 3 topics considered Verbal measures of hill steepness Tell how many degrees… Visual measures of hill steepness Adjust an incline on a disc provided Haptic measure of hill steepness Touch based

Perceptual Constancies in Vision : Perceptual Constancies in Vision Tendency to experience a stable perception in the face of continually changing sensory input People view things as being stable Misleading cues Optical illusions cause us to misread the stimuli around us

Perceptual Constancy : Perceptual Constancy Perceptual Constancy perceiving objects as unchanging even as illumination and retinal image change color shape size

Shape Constancy : Shape Constancy It is hard to tell if the figure on the upper right is a trapezoid or a square slanted backward. If we add texture, the texture gradient helps us see that it is actually a square

Relationship Between Perceived Size and Perceived Depth : Relationship Between Perceived Size and Perceived Depth To perceive the size of objects accurately we must also perceive their distance accurately Thus, many visual illusions occur simply because a particular image lacks sufficient depth cues This figure shows that image size depends upon both object size and distance

Misleading Cues: Optical Illusions : Misleading Cues: Optical Illusions Muller-Lyer Illusion Two linear lines of equal length look different Why? Closer objects appear shorter and farther objects appear longer Result of a combination of size constancy processes and misperception of depth

Perceptual Organization: Muller-Lyer Illusion : Perceptual Organization: Muller-Lyer Illusion

Misleading Cues: Optical Illusions : Misleading Cues: Optical Illusions Ponzo Illusion Same a Muller-Lyer Illusion Upper and lower horizontal lines are same length, but upper appears longer Converging lines convey linear perspective, suggesting the upper line lies farther away Closer objects appear to be smaller

Ponzo Illusion : Ponzo Illusion

Ponzo Illusion : Ponzo Illusion Converging lines indicate that top line is farther away than bottom line

Misleading Cues: Optical Illusions : Misleading Cues: Optical Illusions Impossible Figures Objects that can be represented in two-dimensional pictures, but cannot exist in three-dimensional space Images look fine at first, but are impossible Bottom-up processing

Funky Shape : Funky Shape

Impossible Figure : Impossible Figure

Impossible Figure : Impossible Figure

Impossible Figure : Impossible Figure

Impossible Figure : Impossible Figure

Nutty Nut : Nutty Nut

Slide 55 :

Space Clock : Space Clock

Impossible Figure : Impossible Figure

Slide 58 :

Ladder up or down? : Ladder up or down?

Misleading Cues: Optical Illusions : Misleading Cues: Optical Illusions Moon Illusion Full moon appears to be smaller when overhead Due to size constancy effects and misperception of distance

What do optical illusions reveal about visual perception? : What do optical illusions reveal about visual perception? We form perceptual ideas (hypotheses) about what we perceive. Contextual clues shape those formations of ideas. Human perceptions are not merely reflections of objective reality. We make decisions about what we are perceiving.

Autostereogram : Autostereogram Another way to create the illusion of depth through binocular stereopsis is with an Autostereogram An autostereogram is formed by superimposing two repeating patterns The two patterns are slightly offset, and when viewed properly, this offset is seen as a binocular disparity

Autostereogram : Autostereogram

Perceptual Interpretation : Perceptual Interpretation Perceptual Adaptation (vision) ability to adjust to an artificially displaced visual field prism glasses Perceptual Set a mental predisposition to perceive one thing and not another

Perceptual Set: Schemas : Perceptual Set: Schemas What you see in the center is influenced by perceptual set

Mona Lisa : Mona Lisa

Mona Lisa : Mona Lisa

Perceptual Set: Context Effects : Perceptual Set: Context Effects Context Effects– our stereotypes about gender or culture can color context.

Perceptual Set: Schemas : Perceptual Set: Schemas Flying Saucers or Clouds?

Sense of Hearing: Audition : Sense of Hearing: Audition A distal stimulus (sound): proximal stimulus (sound waves) Sound waves reach the ears Perception and identification of the sound results.

The Stimulus- Sound : The Stimulus- Sound Sound Waves Vibrations Move at fraction of speed of light Generated by vibrating objects and air causing vibrations Waves are characterized like light waves by Amplitude: loudness Wavelength: frequency/pitch Purity: timbre

Sense of Hearing: Audition : Sense of Hearing: Audition Audition the sense of hearing Frequency the number of complete wavelengths that pass a point in a given time Pitch a tone’s highness or lowness depends on frequency Timbre Tone quality Purity of tone

Human Hearing Capacities : Human Hearing Capacities Frequency Measured in cycles per second (Hz) Higher frequencies= higher pitch Humans hear a range of sounds Low 20 Hz to a high of 20K Hz Extreme ends of spectrum are most difficult to hear Various animals can hear higher or lower than the human ear Amplitude Measured in decibels (dB) Greater amplitude= louder sound Perceived loudness doubles about every 10 dB’s.

The Intensity of Some Common Sounds : The Intensity of Some Common Sounds

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Sensory Processing in the Ear : Sensory Processing in the Ear Ears channel energy to the neural tissue that receives it Three sections of human ear External ear Sound conduction based on vibration of air molecules Middle ear Sound conduction based on vibration of movable bones Inner ear Sound conduction based on waves in a fluid

Structure of the Ear: EXTERNAL EAR : Structure of the Ear: EXTERNAL EAR External (Outer) Ear ear lob and auditory canal Pinna: sound collecting cone Sound waves collected by pinna are funneled through the auditory canal toward eardrum Eardrum- taut membrane that vibrates in response to sound waves Pinna

Structure of the Ear: MIDDLE EAR : Structure of the Ear: MIDDLE EAR Middle Ear- chamber between eardrum and cochlea Ossicles: vibrations in the eardrum are sent to this part of ear made up of three tiny bones hammer Anvil stirrup Move in conjunction with each other Amplify tiny changes in air pressure

Structure of the Ear: INNER EAR : Structure of the Ear: INNER EAR Cochlea Fluid filled, coiled tunnel that contains receptors for hearing Snail-like appearance Contains neural tissue of ear Sound enters cochlea through the oval window (vibrated in ossicles) Basilar Membrane Inside cochlea Runs the length of the spiral cochlea Hold auditory receptors Auditory receptors- hair cells DDD INNER EAR: innermost part of the ear, continuing the cochlea, semicircular canals, and vestibular sacs

AUDITORY RECEPTORS : AUDITORY RECEPTORS Hair cells Waves in fluid of inner ear stimulate cells Movement converted into neural impulses sent to brain Routed through the thalamus to the auditory cortex in temporal lobe (mostly) Auditory cortex has specialized cells like the PVC does

Transduction of Sounds : Transduction of Sounds The structures of the ear transform changes in air pressure (sound waves) into vibrations of the Basilar Membrane As the Basilar Membrane vibrates it causes the hairs in the Hair Cells to bend The bending of the hairs leads to a change in the electrical potential within the cell

Auditory Perception:Theories of Hearing : Auditory Perception:Theories of Hearing Place Theory Hermann von Helmholtz (1863) the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated Various hair cells are vibrated by different sound frequencies Brain detects frequency based on area along membrane Frequency Theory 19th Century Theorists the theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch Basilar membrane= drum

Reconciling Place and Frequency TheoriesBoth theories are valid in part : Reconciling Place and Frequency TheoriesBoth theories are valid in part Place Theory Problems Hair cells along the membrane are not independent of one another (vibrate together) Pattern-traveling wave Place Theory Success Waves do peak at specific points based on the frequency of the sound waves. Frequency Theory Problems Research proves that neurons have a difficult time firing at the rate that theorist proposed in theory. Frequency Theory Success Waves peaking at specific points based on the frequency of sound is correct

Auditory Localization: Perceiving Sources of Sound : Auditory Localization: Perceiving Sources of Sound Sometimes we have trouble locating where the sound is coming from. Our ears are set apart and we cannot move them as animals do to locate sound We have to turn our entire head Two cues important in localization of sound Intensity (loudness) of sound Timing of sound

How We Locate Sounds : How We Locate Sounds Sound waves strike one ear sooner than the other and then the brain distinguishes where the sound came from. People who go deaf in one ear have trouble locating sound.

Audition Deficiencies : Audition Deficiencies Conduction Hearing Loss hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea Nerve Hearing Loss hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerve

Hearing and the Elderly : Hearing and the Elderly Hear low frequencies better than high ones Results from nerve degeneration near the beginning of the basilar membrane. Supports place theory’s assumption that different pitches activate different places on the basilar membrane.

Hearing and the Elderly : Hearing and the Elderly Older people tend to hear low frequencies well but suffer hearing loss for high frequencies

Chemical Senses : Chemical Senses TASTE Gustation Gustatory Sense SMELL Olfaction Olfactory Sense

Taste: The Gustatory System : Taste: The Gustatory System Physical stimuli Chemical substances that are soluble Gustatory Receptors Clusters of taste cells found in taste buds Process of Taste Cells absorb chemicals dissolved in saliva Neural impulses are triggered Neural impulses routed through thalamus to cortex Life of Taste Cells Not long 10 days and then replaced by new cells

Taste: The Gustatory System : Taste: The Gustatory System Four Primary tastes Sweet Sour Bitter Salty 5th Sensation Recently Studied UMAMI Flavor associated with monosodium glutamate (MSG) Also found in protein-rich foods, such as meat, seafood, and cheese.

Taste: The Gustatory System : Taste: The Gustatory System Sensitivity distributed unevenly over tongue Sweeter taste=positive reaction Bitter, sour, and salty= less positive reaction Taste changes to accommodate body (biological) Preferences learned (environmental) People vary in sensitivity Super tasters: 4 X’s as many taste buds than monotasters Monotasters: 4 X’s less taste buds than super tasters Women more likely to be super tasters than men

Taste: The Gustatory System : Taste: The Gustatory System Flavor Perception Odor contributes to flavor detection Ability to identify flavors declines noticeably when odor is absent Food tastes bland when you have a cold Papillae Receptors cluster in these small mucous-membrane projections They vary in their sensitivity to taste sensations 3 types of Papillae Circumvallate Foliate Fungiform Sensory Interaction the principle that one sense may influence another as when the smell of food influences its taste

Slide 94 : Each bump on top and sides of tongue are 200 + taste buds Each contains a pore that catches food chemicals Molecules are sensed by 50-100 taste receptor cells that project antenna-like hairs into the pore.

Smell: The Olfactory System : Smell: The Olfactory System Physical stimuli: chemical substances that evaporate and are carried in the air Dissolved in fluid (mucus in nose) Receptors for smell: olfactory cilia (hair like structures located in the upper portion of the nasal passages) Lifespan: Short (30-60 days) Constantly being replaced

Smell: The Olfactory System : Smell: The Olfactory System How do we smell? Axons synapse with cells in the olfactory bulb They are routed through the thalamus Are there classifications of smell (like taste)? No. We can distinguish between 10K different odors When asked to identify we have trouble describing the odors Females are more accurate than males in doing so

Age, Sex and Sense of Smell : Age, Sex and Sense of Smell

Smell: The Olfactory System : Smell: The Olfactory System Smelling a rose Airborne molecules of its fragrance must reach receptors at the top of your nose Sniffing swirls air up to the receptors, enhancing the aroma Receptor cells send messages to the brain’s olfactory bulb, and then, on to the temporal lobe’s primary smell cortex Then to the parts of the limbic system involved in memory and emotion. Smell is the only sensory system that does not get routed through the thalamus.

Smell : Smell Odor Molecules

TOUCH: Tactile Sensation : TOUCH: Tactile Sensation Physical stimuli Mechanical, thermal, and chemical energy impinge on skin Perception of tactile stimulation Warmth Cold pain 60 types of sensory receptors on human skin All specialized in function (like cold and heat)

Touch : Touch Skin Sensations pressure only skin sensation with identifiable receptors warmth cold pain

TOUCH: Tactile Sensation : TOUCH: Tactile Sensation Feeling of Pressure Skin patches responsible of sensation of touch Nerve fibers carry info to spinal cord and brainstem Fibers cross over the body to opposite sides of the brain Tactile pathway Thalamus Somatosensory cortex Brain parietal lobe

TOUCH: Tactile Sensation : TOUCH: Tactile Sensation Feeling Pain Crucial to survival/warning system Pathways to the brain Fast pathway Registers localized pain and relays it to the cortex in a fraction of a second Sharp pain hits when you first cut your finger Depends on A-delta fibers (myelinated neurons) Slow pathway Lags a second or two behind the fast system Conveys less localized, longer lasting aching or burning pain after an injury Depends on C-fibers (thin, unmyelinated neurons)

Puzzles in Perception of Pain : Puzzles in Perception of Pain Influenced by expectation, personality, mood, and other higher mental processes Placebo effect studies done that prove this Distraction of pain lessons the symptoms Gate Control Theory- Melzack and Wall question “How does the central nervous system block incoming pain signals?”

Pain : Pain Gate-Control Theory (Melzack & Wall) theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain “gate” opened by the activity of pain signals traveling up small nerve fibers “gate” closed by activity in larger fibers or by information coming from the brain

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Other neural connections to the blocking of pain signals : Other neural connections to the blocking of pain signals Endorphins Responsible for the results of Placebo effect Acupuncture Researchers are still not sure how endorphins suppress pain. Periaqueductal gray (PAG) Descending neural pathway originating in the midbrain Initiated by endorphins acting on PAG neurons that trigger impulses to release serotonin Synapse occurs in spinal cord and more endorphins are released, inhibiting the activity of pain transmission

Body Position and Movement : Body Position and Movement Kinesthesis the system for sensing the position and movement of individual body parts Vestibular Sense the sense of body movement and position including the sense of balance In inner ear Semicircular canals make up largest part of vestibular system. Movement detected by hair cells.