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146 Cards in this Set
- Front
- Back
Two pure wavelengths
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Red and Blue
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Eye never sees pure wavelengths
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sees blends
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primary eye colors
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red, blue, and green
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why green?
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covers largest spectrum
Red covers shortest spectrum |
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what is hue characterized by?
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saturation or lack of (greying)
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Visual range?
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400 to 700 nm (400 - ultraviolet side, 700- infrared side)
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Luminance?
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The intensity of light at given point (source) as close as you can get to it
measured in Foot Lamberts (FL) |
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Illuminance?
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density of luminous flux on a surface
measured in Foot Candles (FC) |
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Reflectance?
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ratio of the amount of light surfaces either reflect/absorb
Reflectance (%) = Luminance (FL)/ Illuminance (FC) |
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Brightness?
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Defined as "visual intensity"
complexity due to multiple definitions of light intensity measures luminous intensity/flux (unit: candela) distance is key |
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Eye structure
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pupil
lens ciliary muscle - pulls lens in and out to help you see what you're trying to focus on. smooth muscle retina fovea - lots of color, 30 degree range periphery - no color, highly sensitive to light changes, put flashing sensors in peripheral to move fovea range |
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Visual Angles (VA)
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VA = 5.7*60*(Height/distance)
**simplified |
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Factors affecting visual reception
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location on the retina
acuity - ability to resolve fine detail sensitivity to light - too much = headaches color sensitivity to wavelength adaptation - too bright/dark at 1st - then you adapt (beach) Differential wavelength sensitivity |
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Myopia
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Nearsightedness
inability to flatten out lens enough to focus on distance can't see far |
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Presbyopia
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Farsightedness
inability of lens to accommodate very near stimuli can't see near |
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Protanopia
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7% males have
color blindness (1st or 2nd) most prevalent is red-green design rule: design in monochrome first |
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Simultaneous Contrast
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colors change when placed next to each other
effects maps and multi-color displays |
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color contrast doesn't produce good ____
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luminance-contrast ratio
putting a color on a white background and it bleeds |
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aging reduces ____
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the amount of light passing through the cornea, perceived as poor illumination (reducing sensitivity)
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Negative Image
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phenomena to simultaneous contrast leaving prolonged after image (e.g. road glare)
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Decrease contrast
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decrease visibility
e.g. black print on gray |
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decrease illumination
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decrease contrast sensitivity
e.g. reading map in poor light |
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polarity
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black on white better than white on black
e.g. designing viewgraphs |
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spatial frequency
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optimum CS at 3C/D
e.g. ideal size of text font given viewing distance |
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visual accommodation
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CS
e.g. map reading during night driving |
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motion
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decrease CS
e.g. reading a road sign while moving |
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positive contrast
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light text on dark background
increase font size by 25% to gain same effect |
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negative contrast
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dark test on light background
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irradiation (aka bleeding)
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white lettering spreading over dark backgrounds
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upper case lettering
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more difficult to process, less shape variation
looses curvature |
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block print
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more difficult to process, less spatial separation
looses curvature |
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Top down processing
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Experience --> knowledge (expectancies and desires) --> perception
MEMORIES |
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bottom down processing
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stimulus world --> the senses --> perception
WHAT YOU PERCEIVE IN THAT CONTEXT |
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Brain starts depth perception with three cues
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1. Accommodation - lens shapes to focus image
2. binocular conversion - "cross-eye" 3. binocular disparity - comparison on contrasting information received by each eye (Dominate eye) |
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linear perspective
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conveying of parallel lines to distant point
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relative size
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cue based on two objects know to be the same size
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interposition
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near object obscures farther one
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light and shading
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shadows, reflection, illuminating lighting
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texturing gradients
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textured structure from angle WILL change texture density (spatial frequency)
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Normal eye movements
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pursuit
saccadic |
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Eye movement - pursuit
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constant motion to follow moving target
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Eye movement - saccadic
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search movement, more abrupt and discrete
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Saccadic movements
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initiation latency (movement time, speed)
Destination (2 types) Dwell (fixation) controlled by volume of information Useful field view (fovea vision) radius of 2 degree, high accuracy, low sensitivity |
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Predicting time to find objects
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time (t) = [Total # (N) * Inspection time (I)] /2
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parallel search (bottom-up thinking)
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target properties
discriminability from background elements simplicity automaticity |
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implications to system design
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1. knowledge can lead to designer to enhance visibility of targets in dynamic displays
2. limit design clutter 3. knowledge of Top-Down processing alters display structure to make target fields apparent (utilize consistent placement) 4. knowledge will lead to models allowing for prediction of time to find targets 5. knowledge of absolute judge limits levels |
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Classic error detection & prevention
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Goal - improve operator detection of signal to noise
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sensitivity vs. specificity
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sensitivity - ability to find or detect it (effectiveness)
specificity - ability not to find error (test failing) |
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Auditory sound (acoustics) basics
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can be presented as a sine wave
primary components - amplitude = loudness, expressed as ratio of sound pressure, unit - decibels (dB) frequency - pitch |
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Sound Intensity (dB)
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20*log(P1/P2)
where P2 = fixed value near threshold of hearing limit (e.g. "absolute" intensity) |
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Range of pitch
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low = 80 - 250 Hz
flicker = below 80 mid = 250 - 1000Hz high = 1000 - 20,000 Hz ultra = 20,000 - 23,000 Hz |
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Vestibular System (Ear)
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Pinnea
Cartilage Ear Canal Tympanic Membrane - drum portion Malleus Inus Stapes Semicircular Canals - 3 axis (x,y,z) fluid with hairs that move with dynamics of air Cochlea Auditory Nerve |
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loudness vs. sound intensity
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loudness = perception
sound intensity = reality |
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hear vs. listening
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psychological experience --> correlates but not identical
psychological scale equal increase in sound intensity does not equate to same in loudness scale - relates physical intensity to psychological experience unit - sones generally loudness doubles each 10dB increase in intensity Critical levels (thresholds) |
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lower threshold
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minimum intensity of sound that can be heard
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upper threshold
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minimum intensity of sound that damage to the ear can occur
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pain threshold
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minimum intensity of sound that physical pain occurs
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Masking Sound (complex techniques for eliminating sound)
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the minimum intensity difference necessary to ensure that a sound can be heard is around 15dB (above the mask), although this value may be larger if the pitch of the sound to be heard is unknown.
high pitch = more detrimental to low pitch woman's voice is more likely to be masked by male voice |
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Alarms design example
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- tend to be omni-directional
fact: auditory alarms induce a greater level of compliance than visual alarm redundancy (sound, visual, tactile) has had mixed effects based on situational environments |
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cognitive processing of alarms
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automation - good thing to a point
impact of false alarms - "cries wolf", "nuisance alarm", training vs conditioning |
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Speech
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tone (unlike normal noise, very specific, very detailed)
time dependent changes analysis: spectrograph masking effect of noise |
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echoic memory
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allows you to replay over and over until you capture it all (in their voice)
form of photographic memory |
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sources of speech distortion
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clipping the begin/ending of words
reduce bandwidth (mumble) echo/reverberation poor sound quality (speaker) dialect |
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Acoustic Engineering
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product of acoustic physics
techniques include filtering and controlling bandwidth (lower/higher/ranging) voice synthesis - recognizable speech, speech that can be heard in noise, "easy listening" --> reducing processing/extraction difficulty, individual hearing loss |
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stages of hearing loss (non-natural)
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1. loss of sensitivity while noise is present - factory with ear plugs, walk out, take out plugs
2. temporary threshold shift (TTS) - concert 3. permanent threshold shift (PTS) e.g. occupational deafness |
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protecting workers - Standards (ACGIH)
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time weighted average (TWA) - duration based
tradeoff of intensity of noise exposure to duration permissible exposure limit (PEL) - exposure only (Upper limit) |
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protecting workers - Enforcement (OSHA)
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Levels of action
all acceptable TWA >85dB PEL > 90dB If TWA or PEL is greater, need earplugs/protection |
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Actions to protect workers
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1. source - equipment or tool, high pitch more irritating than low rumble
2. environment - industrial more intense than street, controls include separation, dampening, absorption 3. individual - hearing protection - measured (NRR), 2 types, ear plugs and ear muffs |
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% of people annoyed by sound
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highly annoying >70dB
% of people annoyed = 20 + 3.2*(dB-70) |
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Touch (tactile and heptic senses)
referred to as feedback signals |
tactile - interpretation of pressure and texture signals, e.g. temp, rough, sharp, dull, smooth
heptic - interpretation of shape signals (cube or round) |
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Historical design issues
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mechanical vs membrane keyboards
work glove design - protection vs feedback pilot error - similar control for landing gear and flaps designing for the blind virtual reality - suit with inflation pockets (NASA) over cluttered visual displays/alerts |
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proprioception & kinesthesis
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sense that allow the brain to know the orientation and location of your body in space without visual stimulus
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Stimulus (3 way)
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1. muscle contraction
2. joint angle 3. epidermal |
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vestibular senses
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physical structure - 2 sets of receptors (groupings of hairs) deep in the inner ear located in the semicircular canals and vestibular sacs
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Stages of human processing
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1. perceive information about environment
2. central processing 3. response to information |
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Selective Attention - only pay attention to so many things at one time
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e.g. controlled flight into terrain - caused by failure of attention to sources of information
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Factors during channel/source selection
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1. salience - bottom-up - attention capture
2. expectancy (top-down) 3. value (top-down) - sampling of environment with expectations of what to find can directly change source based on observer perceived value 4. effort - e.g. not wanting to move |
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Perception is proceeded by 3 processes:
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1. bottom-up analysis
2. unitization 3. top-down analysis (2 & 3 based on long-term memory that is no longer active) |
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Associations allow for ___
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people to guess what something is based on limited sensory info
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Working memory (aka short-term)
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central executive component - is the attention control system of the body to focus on information sources
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two types of information stored
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1. verbal - "phonological loop"
2. spatial - "visuospatial sketch pad" |
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time stored in working memory
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1. how long (time) -- time between being pulsed or accessed
2. how much (capacity) -- average 7 +- 2 "chunks" 3. how similar -- typical source of error due to confusion 4. attention to keep active -- a resource limited |
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Human Factors issues with working memory
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1. minimize load (avoid long codes/strings of #)
2. provide visual echoes (redundancy) 3. placeholders for sequential task (feedback) 4. exploit "chunking" (lower to upper limits) 5. minimize confusability 6. avoid unnecessary zeroes 7. consider memory limits in instructions (avoid "negatives") |
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Situational Awareness
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ability to process and react to dynamic environmental information (teach in military)
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Divided attention
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division of task to mental activities (lose context with divided attention)
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mental effort inversely proportional to ___
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automaticity (signing your name)
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Multi-dimensional memory - modalities
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auditory vs. visual
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multi-dimensional memory - codes
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spatial vs. verbal
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multi-dimensional memory - stages
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perceptual - working memory vs. response
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multi-dimensional memory - visual channels
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focal vs. ambient
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Interruptions are defined as:
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total interference b/w 2 ongoing tasks
e.g. mental stacking of nurses increased separation has been linked to procedure errors |
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addressing time-sharing overload
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task redesign
interface design training automation |
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Properties of Decision Making
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when a person must make a decision from a list of alternatives
some amount of information available relative to options time frame is relatively long choice associated with uncertainty in the end all about probabilities risk adverse v risk taking behaviors idea of willing to take risk based on uncertainty |
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decision making models - normative model
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based on "utility" with outcome based on decision makers perceived "worth"
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Controlling factors when designing (3)
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1. cue reception & integration
2. Hypothesis generation & selection 3. Plan generation & active choice |
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IMPROVING Human Decision Making
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1. task redesign
2. decision-support system decision trees (simple, not modifiable) spreadsheets (simple, modifiable) simulation (good "what if" scenarios, more complex) Expert systems (computer aided, variable, complex) Displays (embedded support of feedback and cues) |
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Display definition
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a human-made artifact designed to support the perception of relevant system variables and facilitate further processing of information by the user
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Graphical User Interface (GUI)
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typically graphical link that manipulates the display based on response or controls
absorbs more information more rapidly like graphics better than text |
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Display Basics
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purpose - convey task intended to support, goal of task, stimulation "information analysis" by user -- do something to move goal forward
Physical tools - color differentiation, visual objects, auditory |
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13 display design principles - perceptual principles
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make displays legible (or audible)
avoid absolute judgment limits top-down processing redundancy discrimination (similarity causes confusion) |
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13 display design principles - Mental Model Principles
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pictorial realism -- looks like what it is (e.g. folder on computer)
moving parts -- dynamic movements should be compatible with model (spatial pattern, direction - dial running backwards) |
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13 display design principles - Attention Principles
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minimize information access cost - "effort"
proximity compatibility - limit divided attention by placing compatible/complementary displays in the same region (occupy same space) Multiple resource - divide information across two resources or stimulus |
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13 display design principles - Memory principles
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replace memory (learned) with visual information: "knowledge of real world"
predictive aiding - when mental resource is completely consumed we become reactive not proactive consistency - utilize long-term memory |
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Problems with principles:
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clashing (13 contradict)
KEY - understanding importance relative to maintaining balance through tradeoffs) |
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Alerts designed based on three levels of relative to consequence for failure to comply
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Warning - "most critical category"
Caution - "less critical" Advisories - typically visual, not auditory |
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Labels & Symbols (4 criteria)
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1. visibility/legibility
2. discriminability 3. meaningful - problem 4. location relative to enhance unambiguous association with displays |
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Monitoring
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displays for monitoring are those supporting potential changing quantities/values
needs/functions to be set to be watched to be tracked Criteria legibility analog v digital prediction/sluggishness |
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Multiple displays
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"real world" can be complex
display layout -- primary visual area (PVA) |
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Factors for consideration for PVA
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frequency
importance consistency shift process/phase-related operation organizational grouping -- procedure clutter avoidance |
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Heads - Up Display (HUD)
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advantages - keeps eyes on environment, spatial imagery enhances, enhanced depth of display "optical infinity"
Disadvantages - clutters environment, confusion, processing difficult (changing background text) |
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Head Mount Display (HMD)
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similar to HUD
projects directly to one or both eyes problems stem from binocular rivalry |
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configural displays
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allows for monitoring of multiple associated events in a single display
e.g. patient monitor |
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Supervisory displays
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dynamic multiple displays allowing for monitoring of situational awareness with alerts and effective control in both normal and non-routine situations
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control vs. controls
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control is an effort to produce an optimum response constrained by a given criteria or environment
controls are rules or conditions (physical or verbal) designed to return an optimal response given difficulty, speed and needed actions KEY - user response selection |
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5 design principles of response selection
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decision complexity (hick-hyman law)
response expectancy - expectancy only works if we correctly perceive the stimulus compatibility - location and movement speed-accuracy tradeoff feedback - stimulate, monitor, confirmation, instantaneous vs delayed |
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discrete control activation
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physical feel
size (relative) confusion and labeling |
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positioning control devices
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movement time (Fitt's law) - sensitivity (move mouse 1in and on screen moves 6cm)
device characteristics - indirect vs direct, movement, gain task performance dependence work space environment |
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device characteristics - indirect vs direct position control
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direct - something directly attached or you move directly
indirect - move mouse on pad to move mouse on screen |
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device characteristics - movement
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isotonic - free moving
isometric - resistance on levels spring loaded - offers resistance |
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device characteristics - gain
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G = change of cursor/change of control position
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Verbal and Symbolic devices
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numerical data entry - verbal vs manual
linguistic data entry - verbal vs. manual other character/symbol data entry |
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voice input
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disadvantages - cost, confusion & limited vocab, training personnel, training software, speed/reaction/processing time, acoustic quality, noise, stress & tone change, compatibility
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software design cycle
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constant feedback loop - understanding, design, evaluation
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Understanding the System
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frequency of task performed using a particular application
mandatory vs discretionary use knowledge of the level of the user |
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Design to support mental models (4 categories)
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making invisible parts and processes visible to the users
providing feedback building in consistency presenting functionality through a familiar metaphor |
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Dialog styles (variables with impact)
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menus - provides users with a list of items from which to choose one of many
fill-in forms - provides blank spaces for users to enter information question - answer - provides one question at a time and user types answer in field provided command languages restricted natural languages function key direct manipulation |
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design of user support
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manuals
online help systems |
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usability test (reliability engineering, warranty)
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basic elements - systems engineering approach
process - inputs, controls time delays & transport logs - calculate gain, estimate stability metrics - effectiveness, efficiency, user satisfaction testing, cost, interpretation |
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pitfalls of usability testing
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prototypes - don't want to have to recall for more than a region. looking for free usability testing
lab based testing |
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Job stress def
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the harmful physical and emotional responses that occur when the requirements of a job do not match the capabilities, resources, or needs of the worker
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Influences of job stress:
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noise
vibration heat light |
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causes of stress
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environmental stress
psychological stress life stress workload overload fatigue and sleep disruption |
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environmental stressors
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motion (vibration)
thermal stress air quality |
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psychological stressors
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cognitive appraisal - say something in a positive way
ethical issues - avoid level of arousal - level of interest |
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life stress
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strategies for addressing:
keep it simple and focused provided outlets and programs provide counselors |
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workload overload
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timelines - ID task, schedule and assign priority, task demand and resource, multiple resource
hypothetical breaking point - overload consequences mental workload measurement - ID primary and secondary task, psychological measures (objective), subjective measures |
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fatigue and sleep disorders
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vigilance & under arousal
causes of decrement - time, event salience, signal rate, arousal level sleep disorders & disruption - circadian rhythm |
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safety legislation for accidents in the workplace (6)
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1. employer negligence
2. company's argument (normal defense) 3. product liability 4. enforcement agency 5. research and recommendations 6. workman's compensation |
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employer negligence
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failure to exercise a reasonable amount of care, or to carry out a legal duty so that the injury or property damage occurs to another
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Company's argument (normal defense)
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contributory negligence
fellow employee negligence injured employee was aware and assumed risk |
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product liability
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basic position - designed unsafe (inherently unsafe)
manufacturing defect warning defect (not standardized) |
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enforcement agency
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OSHA
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research and recommendations
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NIOSH, ACGIH
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Workman's Comp (Criteria)
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injury from accident/incident
incident occurred due to employment incident occurred during employment |
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Problem - Employees and Risk Taking
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basic - individuals evaluate risk by the event likelihood vs severity of injury - play on recent memory
product use - perceived risk of injury, novelty of hazard and whether exposure voluntary, familiarity of product, cost of compliance |
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2 systems to support healthy behavior
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1. use performance - support systems on job
2. use training systems before job |