Ch 6-7 Psych PDF

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Ch 6-7 Psych Lecture and Textbook Continued...

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CHAPTER 6: Sensation and Perception

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Sensing the World: Some Basic Principles

Sensation and Perception are actually part of one continuous process. o Sensation- the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment o Perception- the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events o Bottom-up processing- analysis that begins with the sensory receptors and works up to the brain’s integration of sensory information o Top-down processing- information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations. At perception level. Ex: when we see our mother our senses just “see” her, our brain is what tells us that it's our mother and that she is important. All of our senses perform these 3 tasks: Receive sensory stimulus Transform the stimulation into neural impulses Deliver this information to our brain o Thresholds § The shades of our own senses just show the tip of the iceberg in the vast awareness of the sea of energy (i.e. other animals detect a world that lies beyond human experience) § Psychophysics- the study of relationships between the physical characteristics of stimuli, such as their intensity and our psychological experience of them § Absolute Thresholds ·

Some kinds of stimuli are extremely sensitive

· Absolute threshold- Gustov Fechner the minimum stimulation needed to detect a particular stimulus 50% of the time including a light, sound, pressure, taste, or odor § Signal Detection · Detecting weak signals depends a lot on our psychological state—our experience, expectations, motivation, and alertness ·

Signal detection theory- theory predicting how and when we detect the presence of a faint

stimulus (signal) amid background stimulation (noise); assumes there is no single absolute threshold and that detection depends partly on a person’s experience, expectations, motivation, and level of fatigue ·

Signal detection can have life or death consequences

o For instance those people who scan luggage to see if they have any potentially harmful objects need to be keen § Studies have shown that after 30 minutes, their ability to catch faint signals decreases

§ Subliminal Stimulation ·

Subliminal- below one’s absolute threshold for conscious awareness

o Subliminal messages are used by promoters, entrepreneurs, and motivators in order to get people to buy their product, make a change in their life, or work harder § These subliminal stimuli can be sensed below our absolute threshold o the sensation of the stimuli is so weak that they are unnoticed, under certain conditions o An invisible word or image can ‘prime’ our response to a later question Subliminal persuasion may produce a fleeting subtle but not powerful enduring effect. § Priming- the activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory, or response o MOST OF OUR INFORMATION PROCESSING OCCURS AUTOMATICALLY, OUT OF

SIGHT, OFF THE RADAR SCREEN OF OUR CONSCIOUS MIND o The consensus regarding whether entrepreneurs can in fact persuade people to buy things subliminally is NO, according to researchers § Difference Thresholds · Difference threshold- the minimum difference between two stimuli required for detection 50 percent of the time; we experience the difference threshold as a “just noticeable difference” (or jnd). On lower stimuli you can hear a change between two low stimuli then two large stimuli · Weber’s law- the principle that, to be seen as different, two stimuli must differ by a constant minimum percentage (rather than a constant amount). For a person to perceive a difference. 2% o Sensory Adaptation § Sensory adaption- diminished sensitivity as a consequence of constant stimulation · i.e. going into a room that smells badly and 10 minutes later not noticing the smell anymore because you are used to it · if we stopped our eyes from moving completely would objects completely disappear that we were staring at, similar to smells that disappear? o According to some experiments, one would see the image vanish Sensory adaptation may even influence our emotions. This phenomenon enables us to focus our attention on informational changes in our environment without being distracted by uninformative background stimulation. · WE PERCEIVE THE WORLD NOT EXACTLY AS IT IS, BUT AS IT IS USEFUL FOR US TO PERCEIVE IT

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Vision(focus mainly on this but read the rest)

o How does our material body construct our conscious visual experience? § Our eyes receive light energy and transform it into neural messages that our brain then processes into what we consciously see · Transduction- conversion of one form of energy into another; in sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brains can interpret

o The Stimulus Input: Light Energy

§ Two physical characteristics of light that help determine our sensory experience of them · Wavelength- the distance from the peak of one light or sound wave to the peak of the next; electromagnetic wavelengths vary from the short blips of cosmic rays to the long pulses of radio transmission · Hue- the dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, etc. · Intensity- the amount of energy in a light or sound wave, which we perceive as brightness or loudness, as determined by the wave’s amplitude o The Eye § Light enters the eye through the cornea, which protects the eye and bends light to provide focus § The light then passes through the pupil, a small adjustable opening surrounded by the iris, a colored muscle that adjusts light intake § Behind the pupil is a lens that focuses incoming light rays into an image on the retina, a multilayered tissue on the eyeball’s sensitive inner surface § The lens focuses on rays by changing its curvature in a process called accommodation · Accommodation- the process by which the eye’s lens changes shape to focus near or far objects on the retina § The retina doesn’t “see” a whole image. Millions of receptor cells convert particles of light energy into neural impulses which are sent to the brain and subsequently reassembled into a perceived, upright-seeming image § The Retina ·

Retina’s buried receptor cells

o Rods- retinal receptors that detect black, white, and gray; necessary for peripheral and twilight vision, when cones don’t respond o Cones- retinal receptor cells that are concentrated near the center of the retina and that function in daylight or in well-lit conditions; the cones detect fine detail and give rise to color sensations The signals activate the neighboring bipolar cells which activate nearby ganglion whose axons make up the nerve which send information to the brain ·

Optic nerve- nerve that carries neural impulses from the eye to the brain

· Blind spot- the point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there

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Cones cluster in and around the fovea

o Fovea- the central focal point in the retina, around which the eye’s cones cluster o Visual Information Processing § Feature detection · Feature detectors- nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement o Feature detectors in the visual cortex pass such information to other cortical areas where teams of cells respond to more complex patterns § Parallel Processing ·

Our brains engage in parallel processing

o Parallel processing- the processing of many aspects of a problem simultaneously; the brain’s natural mode of information processing for many functions, including vision; contrasts with the step-by-step processing of most computers and of conscious problem solving Subdivisions of vision (motion,form,depth,color) are processed simultaneously by neural teams working.

proximity: percieve groups continuity: we perceive smooth images closer: we their are gaps we “fill” in those gaps to see something

· People with stroke or surgery damage to their visual cortex have experienced ‘blind sight,’ a localized field of blindness in part of their visual field o Color Vision Our difference threshold for colors is so low that we can discriminate more than 1 million different color variations § Color, like all aspects of vision, resides not in the object but in the theater of our brains § One of the most intriguing things in the study of vision is how we see the world in color § 1 in every 50 people is colorblind (the 1 is usually male). Usually the red or green cone or both. Vision is monochromatic or dichromatic instead of trichromatic 2 Theories in how we perceive color:

1. § Hermann von Helmholtz and Thomas Young---

· Inferred that the eye must have 3 corresponding types of color receptors for the three primary colors, red, blue, green ·

Years later, researchers confirmed their theory

o Young-Helmholtz trichromatic theory- the theory that the retina contains three different color receptors--one most sensitive to red, one to green, one to blue—which, when stimulated in combination, can produce the perception of any color

2. § Ewald Hering--· Opponent-process theory- the theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision; for example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green The opponent processes helps explain afterimages § Present solution to color vision has 2 stages · Retina’s red, green, and blue cones respond in varying degrees to different color stimuli which verify the first theory and then the signals processed by this verify the 2nd theory · Their signals are then processed by the nervous system/s opponent process cells, en route to the visual cortex Hubel and Wiesel: Individual neutrons(feature) development in the cortex respond to specific features of a visual stimulus. The visual cortex passes this information along to other areas to

perceive specific things like faces Perceptual Organization o When given a cluster of sensations, people tend to organize them into a gestalt § Gestalt- an organized whole; gestalt psychologists emphasized our tendency to integrate pieced of information into meaningful wholes ·

i.e. Necker cube (see page 264)

o OUR BRAIN DOES MORE THAN REGISTER INFO ABOUT THE WORLD o Form Perception § Figure and Ground · Figure-ground- the organization of the visual field into objects (the figures) that stand out from their surroundings (the ground) o Demonstrates that the same stimulus can trigger more than one perception § Grouping ·

Proximity- we group nearby objects together

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Similarity- we group similar figure together

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Continuity- we perceive smooth, continuous patterns rather than discontinuous ones

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Connectedness- because they are uniformed and linked, we perceive them as a single unit

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Closure- we fill in gaps to create a complete, whole object

o Depth Perception § From the 2D images falling in our retina, we somehow organize 3D perceptions § Depth perception- the ability to see objects in three dimensions although the images that strike the retina are 2D; allows us to judge distance ·

This ability is PARTLY innate

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Visual cliff- lab devise for testing depth perception in infants and young animals

§ Binocular Cues ·

Binocular cues- depth cues, such as retinal disparity, that depend on the use of two eyes

o Retinal disparity- a binocular cue for perceiving depth: by comparing images from the retinas in the two eyes, the brain computes distance—the greater the disparity (difference) between the two images, the closer the object

§ Creators of 3D movies simulate or exaggerate retinal disparity by photographing a scene with 2 cameras placed a few inches apart § Monocular Cues ·

How do we judge if a person is 10 meters or 100 meters away?

o Monocular cues- depth cues, such as interposition and linear perspective, available to either eye alone. Relative size, interposition, relative height, relative motion, linear perspective, light and shadow

o Motion Perception § The brain perceives continuous movement in a rapid series of slightly varying images (called stroboscopic movements) § Phi phenomenon- an illusion of movement created when two or more adjacent lights blink on and off in quick succession OUR BRAIN CONSTRUCTS OUR PERCEPTIONS o Perceptual Constancy § Perceptual constancy- perceiving objects as unchanging (having consistent shapes, size, lightness, and color) even as illumination and retinal images change § Shape and Size Constancies ·

Thanks to shape constancy, we perceive the form of familiar objects

· Thanks to size constancy, we perceive objects as having a constant size, even while our distance from them varies § Lightness Constancy ·

Lightness constancy---

o We perceive an object as having a constant lightness even while its illumination varies § Perceived lightness depends on relative luminance § Color Constancy · Color constancy- perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object ·

Perceptual Interpretation

o Sensory Deprivation and Restored Vision § Experience guides, sustains, and maintains the brain’s neural organization § In both humans and animals, a similar period of sensory restriction does no permanent harm if it occurs later in life · i.e. cover the eye of an animal for several months during adulthood, and its vision will be unaffected upon removal of the eye-patch o Perceptual Adaptation § Perceptual adaptation- in vision, the ability to adjust to an artificially displaced or even inverted visual field § George Stratton’s experiment--- wore optical headgear that inverted up and down, left and right, etc. for 8 days…at first he was depressed and disoriented, but by the 8th day he had completely gotten the hang of it; after taking them off, he adapted to reality quickly o Perceptual Set § Perceptual set- a mental predisposition to perceive one thing and not another § What determines our perceptual set? · Through experiences we form concepts, or ‘schemas,’ that organize and interpret unfamiliar information § Context Effects · A given stimulus may trigger radically different perceptions, partly because of our differing set, but also because of the immediate context o i.e. a 6’9” basketball player looks short in the picture, only because he is being guarded by the

tallest man in the world standing at 7’9” ·

The effects of perceptual set and context show how experience helps us construct perception

§ Emotion and Motivation ·

Perceptions are also influenced by our emotions

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Motives also matter in perception

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Emotions color our social perceptions

o i.e. a spouse who feels loved and appreciated perceive less threat in stressful marital events —“he’s just having a bad day” ·

perception is BOTH INNATE AND LEARNED

o Perception and the Human Factor § Human factors psychology- branch of psychology that explores how people and machines interact and how machines and physical environments can be made safe and easy to use § Understanding human factors can do much more than enable us to design for reduce frustration; it can help prevent accidents and avoid disaster § IMPORTANT: Designers and engineers should consider human abilities and behaviors by designing things to fit people, user-testing their inventions before production and distribution, and being mindful of the cure of knowledge

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Hearing

o Audition- the sense or act of hearing o The Stimulus Input: Sound Waves § Ears transform vibrating air into nerve impulses, which our brain decodes as sounds; the strength or amplitude determines their loudness § Frequency- number of complete wavelength that pass a point in a given time § Pitch- a tone’s experienced highness or lowness; depends on frequency § We measure sound in decibels o The Ear § Human ear converts sound waves into neural activity through a mechanical chain reaction ·

First, the visible outer ear channels the sound waves through the auditory canal to the

eardrum, a tight membrane that vibrates with the waves; the middle ear then transmits the eardrum’s vibrations through the piston to the cochlea; the vibrations cause the cochlea’s membrane to vibrate, jostling that fills the tube; this causes ripples in the basilar membrane, bending the hair cells lining its surface; hair cell movement triggers impulses in the adjacent nerve cells, whose axons converge to form the auditory nerve, which sends neural messages to the temporal lobe’s auditory cortex! o Damage to hair cells accounts for most hearing loss o Males’ greater noise exposure may be the reason why men’s hearing tends to be less acute than women’s o Middle ear- chamber between the eardrum and cochlea containing three tiny bones (hammer, anvil, and stirrup) that concentrate the vibrations of the eardrum on the cochlea’s oval window o Cochlea- a coiled, bony, fluid,-filled tube in the inner ear through which sound waves trigger nerve impulses o Inner ear- the innermost part of the ear, containing the cochlea, semicircular canals, and vestibular sacs § Perceiving Loudness ·

The brain can interpret loudness from the number of activated hair cells

§ Perceiving Pitch ·

Current thinking on how we discriminate pitch combines two theories

o Herman von Helmholtz’s place theory § Place theory- in hearing, the theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated · Problem with place theory is that it explains how we hear HIGH pitched sounds, but not how we hear LOW pitched sounds o Frequency theory suggests an alternative explanation § Frequency theory- in hearing, 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 ·

Explains how we perceive low frequency sounds

§ Locating Sounds ·

Two ears are better than one because it helps discover the more intense sounds sooner

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Humans don’t do very well at locating a sound that is equidistant from both ears

o This is because the sound strikes the two ears at the same time

o Hearing Loss and Deaf Culture § The ear’s intricate and delicate structure makes it very vulnerable to damage · Conduction hearing loss- hearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea · Sensorineural hearing loss- hearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerves; also called nerve deafness § For now, the only way to restore hearing for people with nerve deafness is a sort of bionic ear---a cochlear implant · Cochlear implant- a device for converting sounds into electrical signals and stimulating the auditory nerve through electrodes threaded into the cochlea o Use of such devices is hotly debated § One side wants their kids who are deaf to be able to hear normally § The other side thinks that implants should be used before developing one’s language ·

Other Important Senses

o Touch § Four basic skin sensations: ·

Pressure

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Warmth

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Cold

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Pa...