(contains all the relevant vocabulary from textbook chapters 5 and 6)
Sensation/Perception
sensation: detecting physical energy (a stimulus) from the environment and converting it to neural signals
perception: select, organize and interpret our sensations, enabling us to recognize meaningful objects and events
- experiences and expectations influence our perceptions
bottom-up processing: analysis of stimulus starts in sense receptors and works its way up to brain/mind
top-down processing: information processing guided by higher-level mental processes
- as we construct perceptions, we draw on our experiences and expectations
- THE CHT example, the forest has eyes painting
- our senses are tailored to help us survive (frogs have sensors for small, dark, moving objects)
Psychophysics: relationship between physical characteristics of a stimuli and the psychological experience associated with them
examples: (sound-->volume), (pressure-->weight), (sugar-->sweetness), (light-->brightness)
Detection
absolute threshold: minimum stimulation needed to detect a stimulus 50% of the time
signal detection theory: there are factors that influence absolute threshold
- no single absolute threshold is always true
- person's experience expectations, motivation, fatigue, affect result of SDT matrix
- subliminal messages can still effect thoughts or feelings
- experiment primed people subliminally by flashing a brief image of either something nice, or something bad, and then asking them to judge a face. Those who were flashed the positive image were nicer in their judgments than those who were flashed the negative image, even though neither were aware that they had seen the picture.
- we process images and information unconsciously
- advertisers tried to take advantage of this phenomenon, but it didn't work: subliminal messaging works only in the short-term
- JND (just noticeable difference)
- after constant exposure, our nerve cells fire less often
- in everyday life, our eyes are always twitching to prevent sensory adaptation
- top-down processing: brain filters out most of our sensations from conscious awareness
- foot falling asleep-- when you wake it back up, for the first few moments you feel all of the sensations that are normally tuned-out
- phototransduction: conversion of light energy to understandable neural impulses
- wavelengths= higher frequency-blue, lower frequency-red
- intensity= how much energy was in wave (brightness)
- large amplitude-bright, small amplitude-dull
- saturation= monochromatic light mixes in with colors
- structure of the eye
- cornea: transparent tissue where light enters eye
- iris: muscle that explands/contracts to change pupil size depending on light
- lens: focuses the light rays on the retina
- cataracts= clouding of lens: lens must be removed and replaced by plastic one
- nearsighted-can see close things, farsighted-can see far things
- retina: contains sensory receptors that process visual info and send to brain
- light-sensitive inner surface contains rods and cones
- bipolar cells receive info from ganglion cells which process info
- Optic Nerve: carries neural impulses from the eye to the brain (thalamus)
- blind spot- where optic nerve leaves retina, there are no receptors
- flovea: central point in retina around which cones cluster
- cones: receptors that detect color, detail
- rods: receptors that are sensitive to movement, faint light, peripheral
- there is no color in your peripheral vision
- feature detection: nerve cells respond to specific shapes
- motion after-effects: stare at spiral, then at face-- face seems to move
- sensory adaptation: neurons become used to motion, become fatigued
- different nerves stimulated from perception of different things
- parallel processing: brain divides vision into color, motion, form, depth
- analyze all at once, but separately
- note: red blue and green are not the traditional primary colors, but for light (and vision) they are. The reason? When you mix colors in a subtractive fashion, such as with paints, red, blue and yellow will make a black color. If you mix colors in an additive fashion, such as with lights, red, blue and green makes white.
- MacNichol, Wald and Brown discovered that cones are red, blue or green
- if you are genetically color blind, you lack a certain kind of cone
- long term exposure above 85 decibles produces hearing loss
- differences of as small as 1/100,000 of a second can be detected
- conduction hearing loss: caused by damage to the mechanical system that conducts sound waves (ear drum, hammer anvil, stirrup)
- sensorineural hearing loss/nerve deafness): caused by damage to the cochleas receptor cells or auditory nerve
- cochlear implants are electronic, allow brain to receive sounds
- pain results from injury or damage to the body- rare disease stops feeling pain
- "pain is in the brain"= pain is a subjective thing
- gate-control theory: melzak and wall- spinal cord has neurological "gates" that can block pain or allow it to be sensed
- relieve pain by massaging area: creates competing stimulation in area and blocks some of the receptors that would receive pain signals
- reduce pain: drugs, surgery, acupuncture, exercise, hypnosis, relaxation, distraction
- synesthesia: stimulation in one sense causes sensation in another-- seeing letters with colors, feeling shapes on skin when eating, tasting sounds etc.
- women have better sense of smell, sense declines with age
- brain area for smell (olfactory bulb) very close to brain region for memory
- we often strongly associate smells with certain memories
- vestibular sense- monitors body position
- vision and balance interconnected
- it takes more neural calculations to walk than it does to reason
- we can only process 40 bits/second-- prevents sensory overload
- still unconsciously process other bits (cocktail party concious radar)
- change blindness: even when looking at something, you don't notice it changing
- change deafness: unable to notice voice changing while listening to words
- choice blindness: choose photo, experimenter hands you different photo and you don't notice the change
- mind-sight: gut/unconscious feeling that something is changing
- we tend to overestimate height/vertical
- kinesthetic can also capture vision (dark closet waving hand example)
- form perception: organize visual field into objects that stand out (foreground v. background)
- grouping: organize figures into groups based on proximity, similarity, continuity, connectedness
- closure: fill in gaps to see whole image
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- depth perception: judge distances-- visual cliff experiment with babies
- retinal disparity- images from two eyes differ slightly
- convergence- neuromuscular cues: eyes converge to view close object
- relative size- if two objects are similar in size, but one looks small, we assume it is in the distance
- interposition- objects that block other objects look closer
- relative clarity- hazy things look farther away (because distance is hazy)
- texture gradient- indistinct, fine texture signals distance
- relative height- objects higher in field of vision seem farther away
- our senses are made to suit our needs (we hear pitch of baby cry most clearly)
- signal detection theory: predicts how and when we detect the presence of a faint stimulus amid background stimulation-- depends on person's experience, expectations, motivation, level of fatigue
- subliminal message can briefly prime your response to a later question
- showed people pictures of faces after a half-second flash of either a gruesome or a happy subject, then asked people to rate the faces
- if they were showed a gruesome image, they rated the faces lower
- weber's law: difference threshold is not a constant amount but some constant proportion of the stimulus
- the only reason that even if we stare at something, our sight doesn't adapt and make it disappear from our sight, is because our eyes quiver ever so slightly
- accommodation: process by which lens changes shape to focus images
- acuity=sharpness of vision, affected by distortions in eye
- nearsightedness: focuses distant objects in front of retina, making them blurry
- farsightedness: light rays from near objects reach retina before fully focused
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| example of the SDT matrix
subliminal threshold: when stimuli are below absolute threshold
difference threshold: minimum difference between stimuli required for detection
Weber's Law: two stimuli must differ by a constant minimum percentage to be perceived as different
examples: (light--8%), (weight--2%), (tone--3%)
sensory adaptation: diminished sensitivity to an unchanging stimulus/ we unintentionally ignore unchanging stimulus (band-aid, smell of room)
Transduction
transduction: transformation of stimulus to neural impulses
Color
trichromatic theory: helmholtz+ behavioral studies-- there are three types of cones in the retina, they are sensitive to red, blue and green
opponent process theory: Hering proposed that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision-- one type of cell, for example, is stimulated by read but inhibited by green
color constancy: color of an object remains the same under different illuminations
Sound
acoustical transduction: conversion of sound waves into the neural impulses in the hair cells of the inner ear
frequency/pitch-- wavelength (short waves=high frequencies)
intensity/volume-- amplitude (high amplitude=loud sound)
Sound localization: since we have two ears, sounds that reach one ear before the other help us pinpoint the location of that sound (using factors of intensity and time)
Hearing loss-- conduction v. sensorineural
Touch
four sensations: pressure, warmth, cold, pain-- different combinations make different sensations (itchy is a certain pain receptor, hot is warm and cold at same time)
Taste
five sensations: sweet, salty, sour, bitter, umami (savory, meat)
sensory interaction: smell of food affects taste
Smell
chemical sense: odorants enter nasal cavity to stimulate 5 million receptors
Kinethesis
sense of our body part's positions and movements (nerve endings send signals when we move)
Perception
perception: how brain gives meaning to sensations
selective attention= perceptions change from one moment to another- 11,000,000 bits of neural impulse/second
in-attentional blindness: don't see things we don't care about
perceptual illusions: studying faulty perception
visual capture: when competing with other senses, vision takes control
gestalt= our tendency to integrate pieces of information into a meaningful whole
binocular cues
monocular cues
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textbook notes: sensation and perception (pgs. 197-269)
Chapter 5: Sensation bottom-up processing: sensory analysis that starts at the entry level top-down processing: sensations based on our experience and expectations
transduction: transforming of stimulus energies into neural impulses that our brains can interpret
Thresholds
absolute threshold= minimum stimulation necessary to detect a light, sound, pressure, taste, odor 50% of the time
subliminal stimulation= when stimuli are detectable less than 50% of the time
difference threshold= minimum difference between two stimuli required for detection
Sensory Adaptation
diminishing sensitivity to an unchanging stimulus-- after constant exposure to a stimulus, nerve cells fire less frequently
Vision
wavelength: distance from one peak to the next-- determines hue
amplitude: height of each wave/amount of energy-- determines brightness
Cornea: protects eye and bends light to allow focus
pupil: adjustable opening in the center of the eye that allows light to enter
iris: ring of muscle tissue around the pupil that controls size of pupil opening
lens: transparent structure behind pupil that changes shape to focus images on retina
retina: light-sensitive inner surface of eye, contains receptor rods and cones+ neurons
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