CHAPTER 8: SENSATION AND PERCEPTION. SECTION 1: SENSATION.

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CHAPTER 8: SENSATION AND PERCEPTION

Transcript of CHAPTER 8: SENSATION AND PERCEPTION. SECTION 1: SENSATION.

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CHAPTER 8: SENSATION AND PERCEPTION

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SECTION 1: SENSATION

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WHAT IS SENSATION?

• Def: what occurs when a stimulus activates a receptor

• Stimulus: an aspect of or change in the environment to which an organism responds

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SENSATION CONTINUED• Perception:

organization of sensory info into meaningful experiences

• Psychophysics: study of the relationships between sensory experiences and the physical stimuli that cause them

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THRESHOLD

• Absolute threshold: the weakest amount of a stimulus that a person can detect half the time

• Humans have a very limited range

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SENSORY DIFFERENCES

• Difference threshold: the smallest change in a physical stimulus that can be detected between 2 stimuli

• Just Noticeable Difference (JND): the smallest increase or decrease in the intensity of a stimulus that person can detect

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WEBER’S LAW

• For any change in a stimulus to be detected, a constant proportion of that stimulus must be added or subtracted

• A.K.A.: Weber-Fechner Law

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SENSORY ADAPTATION• Senses are tuned to

change• Senses adapt to a

constant level of stimulation

• Necessary to ignore mundane

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SIGNAL-DETECTION THEORY• Def: the study of

people’s tendencies to make correct judgments in detecting the presence of stimuli

• Radar operator

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PROCESSING STIMULI

• Preattentive process: extracting information automatically

• Attentive process: procedure that considers only one part of the stimuli presented at a time

• Stroop Interference Effect

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SECTION 2: THE SENSES

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VISION

• Most studied sense• Pupil: opening in the iris

that regulates the amount of light entering the eye

• Lens: flexible structure that focuses light on the…

• Retina: innermost coating of the back of the eye, containing light sensitive receptor cells

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VISION CONTINUED

• Cones and Rods: light receptors in the retina; convert light energy into neuronal impulses

• Cones: color• Rods: night vision• Optic Nerve: the nerve

that carries impulses from the retina to the brain

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COLOR DEFICIENCY

• Affects 8% of American men; <1% women

• Dysfunctional cones• Red-green• Yellow-blue• Total deficiency: see in

black and white

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BINOCULAR FUSION

• Def: the process of combining the images received from the two eyes into a single, fused image

• Retinal Disparity: the differences between the images stimulating each eye

• Essential for depth perception

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NEARSIGHTEDNESS

• Eyeball is longer than normal

• Objects focused at a point in front of the retina

• See objects that are near, but not far

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FARSIGHTEDNESS

• Eyeball is too short• Objects focused slightly

behind the retina• Distant objects are

clear, near objects are not

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HEARING

• Sound waves: vibrations in the air

• Loudness determined by amplitude (height) of waves

• Strength determined by decibels

• >110 decibels damages hearing

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HEARING

• Pitch depends on sound wave frequency (rate of vibration of medium through which wave travels)

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PATH OF SOUND

• Outer ear (pinna) receives waves

• Auditory canal vibrates which vibrates the ear drum

• Middle ear: 3 tiny bones---hammer, anvil, and stirrup

• Inner ear: cochlea---liquid moves, tiny hairs detect motion, translate into neuronal input and sent to brain by the Auditory nerve

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DEAFNESS

• 2 types:• 1) Conduction deafness:

hindered physical motion in the outer or middle ear

• Helped with conventional hearing aid

• 2) Sensorineural deafness: damage to the cochlea

• Helped with cochlear implant

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BALANCE

• Vestibular system: 3 semicircular canals that provide the sense of balance, located in the inner ear and connected to the brain by a nerve

• Fluid in canals moves• Hair cells translate

motion

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SMELL

• Chemical sense• Gaseous molecules

contact smell receptors• Olfactory nerve: carries

smell impulses from the nose to the brain

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TASTE

• 5 primary tastes:• 1) Sweet• 2) Sour• 3) Bitter• 4) Salty• 5) Umami (savory, meaty)• Combination of these

creates flavor• Taste is more determined

by smell

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SKIN SENSES

• Densely bundled nerve endings create sensitivity to pressure

• Some are sensitive to hot and cold

• Pain results from many different stimuli

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PERCEPTIONS OF PAIN• Sharp, localized pain

immediately after injury• Dull, generalized pain

later• Gate control theory of

pain: shifting attention away from pain can lessen its effects

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BODY SENSES

• Kinesthesis: the sense of movement and body position

• Cooperates with vestibular system and vision

• Receptors in and near muscles, tendons, and joints

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SECTION 3: PERCEPTION

The way we interpret sensations and organize them into meaningful experiences

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GESTALT

• Def: the experience that comes from organizing bits and pieces of info into meaningful wholes

• Trying to identify principles the brain uses in building perception

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GESTALT PRINCIPLES

• 1) Proximity• 2) Continuity• 3) Similarity• 4) Simplicity• 5) Closure• If elements are close to

one another or similar, we perceive them as one set

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FIGURE-GROUND PERCEPTION• The ability to

discriminate btwn a figure and its background

• Shows we can perceive in more than one way

• Works with sound as well

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PERCEPTUAL INFERENCE• Filling in the gaps in

what our senses tell us• Largely automatic and

unconscious• Depends on experience

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LEARNING TO PERCEIVE• Influenced by needs,

beliefs, and expectations

• If we want something, we’re more likely to see it

• Perceptual set: twisting truth to fit our own belief system

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SUBLIMINAL PERCEPTION• Subliminal messages:

brief auditory or visual messages that presented below the absolute threshold

• Not really effective

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DEPTH PERCEPTION

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MONOCULAR DEPTH CUES• Can be used with a

single eye• Relative height: objects

further away are higher on your visual plane

• Interposition: overlapping

• Light and shadows: brightly lit objects are closer

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MORE MONOCULAR CUES• Texture-density

gradient: close objects have more detail

• Motion parallax: the apparent movement of stationary objects relative to one another that occurs when the observer changes position

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MORE MONOCULAR CUES• Linear perspective:

parallel lines converge in the distance

• Relative motion: near objects appear to move in the opposite direction that you do; far objects seem to travel with you

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BINOCULAR DEPTH CUES• Depend on movement

of both eyes• Convergence: eyes turn

inward when looking at nearby objects

• Retinal disparity• Large disparity means

close; small means far

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CONSTANCY

• Def: the tendency to perceive certain objects in the same way regardless of changing angle, distance, or lighting

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ILLUSIONS

• Def: perceptions that misrepresent physical stimuli

• Happens when perceptual cues are distorted so our brains cannot correctly interpret space, size, and depth cues

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EXTRASENSORY PERCEPTION

• Def: (ESP) an ability to gain info by some means other than the ordinary senses

• 4 types:• 1) Clairvoyance: perceiving

w/o sensory input• 2) Telepathy: mind reading• 3) Psychokinesis: move

things with your mind• 4) Precognition: foretell

events

I’m a big idiot who likes to rob people of their

money by preying on their

personal loss