Psychology 2990A/B Chapter Notes - Chapter 8: Mental Model, Display Device, The Young Professionals
30 Apr 2018
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Chapter 8- The Design of Displays:
• Could perceive indivd elements but ability perceive overall meaning info hindered poor
integration displays
• Various sensory systems (primarily eyes and ears) process raw sensory info and use info
bottom-up basis perception- interp meaning of info, w assistance expectancies and
knowledge driving top-down mem
• Perceived mem processed and stored temp working mem/ permanently long-term mem
and used diagnosis and decision making
• Displays- typ human-made artifacts designed support perception relv system variables
and facilitate further processing of that info= convey various forms info used various
tasks
• Concept display closely linked w graphical user interface (GUI)- former includes text,
while GUI describes graphics and includes controls and responses used manipulate
display
• Display acts as medium b/w some aspects actual info in system (or action requested of
operator) and operator’s perception and awareness what system doing, what needs be
done and how system functions (mental model)
Ways of classifying displays:
• Physical implementation of display device- physical tools designer has to work w in
creating display
• Before fabricating display, designer must ascertain nature task the display intended
support- dif displays may be optimally suited for dif tasks
• Once task and goals ident must do detailed info analysis to ident what operator needs to
know to carry out task
• No single display tool best suited all tasks b/c characteristics human user who must perf
task
• Key mediating factor det best mapping b/w physical form of display and task
requirements is series of principles of human perception and info processing- grounded in
strengths and weaknesses human perception, cog and performance and through careful
application of principles to output of info analysis best displays emerge
Thirteen principles of display design:
Perceptual principles:
1. Make displays legible (or audible)- legible and audible displays nec, not sufficient, for
creating usable displays- once legible, add perceptual principles should be applied
2. Avoid absolute judgements- don’t require operator judge level represented variable on
basis single sensory variable, like color, size/ loudness, contains more than 5-7 poss
levels- require greater precision as in color-coded map w 9 hues invite errors judgment
3. Top-down processing- perceive and interpret signals in accordance w what expect
perceive on basis past exp- signal contrary expectations, like warning/ alarm unlikely -
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event, more physical evidence signal must be presented to guarantee interpreted
correctly. Sometimes expectancies based long-term mem but expectations based
intermediate context of encountering series “on” messages inviting final line perceived as
on (see pg. 224)
4. Redundancy gain- viewing/ listening conditions degraded, message more likely be interp
correctly presented more than once- part true if alt physical forms (tone and voice, voice
and print, print and pics, color and shape), redundancy not simply same as repetition. Alt
physical forms used, greater chance factors might degrade one form (noise degrading
auditory message) will not degrade other (printed text)- traffic light good redundancy
gain (position and hue redundant)
5. Discriminability. Similarity causes confusion: Use discriminable elements- causes 2
signals be similar is ratio of sim feats to dif feats, where confusion could be serious=
delete unnec sim feats and highlight dissim (dif) ones in order create distinctiveness, poor
legibility also amplifies neg effects of poor discriminability
Mental model principles:
• When operators perceive display, often interpret what display look like and how moves in
terms of expectations/ mental model of system being displayed, a concept- good for
format of display to capture aspects user’s correct mental model, based on user’s exp
system whose info being displayed
6. Principle of pictorial realism- display should look like variable represents- contains
multiple elements these elements can sometimes be configured in manner looks like how
configured in env represented (or how operator conceptualizes env)- temp high to low,
thermometer should be oriented vertically
7. Principle of moving part- moving element(s) any display of dynamic info should move in
spatial pattern and direction compatible w user’s mental model how rep element actually
moves in physical system ex: plane moves up gain altitude, moving element altimeter
should move upward w increasing altitude
Principles based on attention:
• Selective attention- may be nec choose displayed info sources nec given task
• Focused attention- allow sources be perceived w/o distraction from neighbouring sources
and divided attention- parallel processing (2/ more) sources info concurrently if task
requires
8. Minimizing information access cost- typ cost in time and effort move selective attention
one display location to another to access info- min net cost by keeping frequently
accessed sources in location cost traveling b/w them is small, keep displays small so little
scanning required access full info (but can degrade legibility- need be careful)
9. Proximity compatibility principle- sometimes 2/more sources info rel same task and must
be mentally integrated complete task, divided attention b/w 2 sources for 1 task nec=
close mental proximity- should be close in proximity so info access cost low ex: display
common colour, link together w lines/ pattern. Too much close display proximity not
always good, part if one elements must be subject focused attention- don’t overlap.
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o Lower mental proximity of focused attention task is best served by low display
proximity of separation
o Mental proximity high (divided attention for integration), display proximity
should also be high (close)
o If MP low (focused attention), DP can, and sometimes should, be lower
10. Principle of multiple resources- sometimes processing lot info can be facilitated by
dividing info across resources- presenting visual and auditory info concurrently
Memory principles:
• Human mem vul esp working mem- lim capacity and can forget easily if can’t write
down and long-term vul b/c forget certain things/ remember others too well and persist
doing them when shouldn’t
11. Replace memory with visual info: Knowledge in the world-people ought not required
retain important info solely in working mem/ retrieve from long-term mem, sometimes
too much knowledge in world can lead clutter probs and systems designed rely on
knowledge in head not nec bad ex: using computer systems, experts might like to be able
retrieve info by direct commands (knowledge in head) than rely on knowledge through
menu (knowledge in world)- need to balance both
12. Principles of predictive aiding- mental resources consumed other tasks, prediction falls
apart and become reactive, responding to what already happened, rather than proactive,
responding in anticipation of future- proactive more eff- displays can predict what will
(or likely to) happen gen quite eff supporting human perf= removes resource-demanding
cog task and replaces w similar perceptual one
13. Principle of consistency- long-term mem works too well, may cont trigger actions no
longer approp= instinctive and automatic human tendency- no way avoid, good designs
should try incorp manner consistent w other displays user may be perceiving
concurrently/ may have perceived recent past ex: colour coding consistent where red
means same thing and dif display panels should be consistently organized, reducing info
access cost each time new set encountered
Conclusion:
• Principles sometimes conflict/ collide- no easy solution say which principles more
important than others when 2/more principles collide but clever and creative design can
sometimes enable certain principles be more effectively served w/o violating others
Alerting displays:
• Critical to alert operator part cond, omnidirectional auditory channel best- dif levels
seriousness of cond be alerted, not all need/ should be announced auditorily
• 3 levels alerts:
o Warning- most critical category, should be signaled salient auditory alerts
o Cautions- may be signaled auditory alerts less salient (ex: softer voice signals)
o Advisories- don’t need to be auditory at all, can be purely visual
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Document Summary
Sometimes expectancies based long-term mem but expectations based intermediate context of encountering series on messages inviting final line perceived as on (see pg. Alt physical forms used, greater chance factors might degrade one form (noise degrading auditory message) will not degrade other (printed text)- traffic light good redundancy gain (position and hue redundant: discriminability. Conclusion: principles sometimes conflict/ collide- no easy solution say which principles more important than others when 2/more principles collide but clever and creative design can sometimes enable certain principles be more effectively served w/o violating others. Icons may be advantageous word labels read those not fluent lang and sometimes under degraded viewing conds, redundancy gain provide usually of value but use icons alone= unnec risk when comprehension important (same abbreviations). Space small effort should be made link key to verbal label may be presented next to key: location- should be physically close to and unambiguously associated w entity label, adhering to proximity compatibility principle (overlooked).
