Human Capabilities:
Perception, Attention
CS352
Announcements
• Notice upcoming due dates (web page).
• Where we are in PRICPE:
– Predispositions: Did this in Project Proposal.
– RI: Research is in process (studying users), due
Friday. Should lead to Insights.
– CP: Concept and initial (very low-fi) Prototypes
due soon!
– Evaluate throughout, repeat iteratively!!
2
Study the User:
Some Attributes
• Physical attributes
(age, gender, size, reach, visual angles, etc…)
• Perceptual abilities
(vision, hearing, heat sensitivity…)
• Cognitive abilities
(memory span, reading level, musical training, math…)
• Personality and social traits
(likes, dislikes, preferences, patience…)
• Cultural and international diversity
(languages, dialog box flow, symbols…)
• Special populations, (dis)abilities
• And of course Space/objects/technology
(table height, sound levels, lighting, software version…)
Design Implications/Insights
Population
Implications
Users 16-80 yrs
Range of text sizes
Range of grip strength
Some French speakers
Multilingual interface
Astronaut users
Extensive training available
Military context
Aesthetics less of an issue
Ruggedness is critical
Perception and the Senses
– Senses: smell, taste, sight, hearing, touch,
proprioception (body position awareness), pain,
temperature, balance, ...
– Change:
• Adaptation: Senses physically react to change.
• Absence of change leads us to lose sensitivity.
• Eye compensates for this some by shifting around, but
nose can't do that (which is why we become
sensitized to a smell).
– But: there is a “just noticeable difference” (jnd)
• eg: Doubling # photons does not double perceived
intensity of a picture.
Perception
• How information is acquired from the world by senses
– they are the input devices to the brain
– so, if doesn’t make it thru senses => not delivered to brain.
• Obvious implication is to design representations that
are readily perceivable
• Q: How can we tell when they are and when they
aren’t?
– A: see next slides.
Visual perception
• Eye: Pupil/lens,
place image on retina.
From there, to brain.
– Retina has photoreceptor
cells: rods and cones.
– Rods: tell us dark vs. light. Can detect in very
dim light. Lots of rods (120M).
– Cones can detect color. But need much light
to do this. Only a few cones (6-7M).
• 64% of cones see red, 32% see green, only 2%
see blue.
Colors
• Color-blindness
– Red/green color blindness most
common: 7-8% of males red from green,
0.4% of women.
• Excessive/gratuitous colorings
– distracting
– unprofessional
– impart meaning where none/different intended
Interface Hall of shame: Compuserve's WinCim 2.0 application
Basic Principles
• Hue (“color”)
– eg, Red
Light
• vs. light
– “how much light it reflects” (regardless
of hue)
– eg: closeness to black
• vs saturation (“how much paint you
added”).
Not much light
Contrast – Howto’s
• Choose 1 hue, from light recommended
hues, lighten, desaturate
• Choose 2nd hue from
dark recommendations,
darken, saturate.
Effective
Not as
effective
Not as
effective
And not adjacent colors.
Which is easiest to read and
why?
What is the time?
What is the time?
What is the time?
What is the time?
What is the time?
Other senses
– Sound (hearing):
• Pitch – frequency, loudness – amplitude, location
• We are good at sound! We have a lot of
bandwidth, in part because of language facilities.
• UIs can use when appropriate
– but can hog our attention.
– Touch:
• Pressure, pain, temperature (hot/cold).
– Potential for use in advanced UIs.
– Motor system (input & output system): Often
causes errors: wrong button, double-click vs.
single-click, ...
Perception take-aways 1
• Some UI devices/paradigms leverage
more senses than others.
– eg: WIMP?
– eg: (fairly basic) cell phone?
– eg: iPhone?
– eg: Wii?
Perception take-aways 2
• These are pre-brain!
– If you want info to get to/from brain, has to
make it thru senses first.
– These are the human UI to the brain.
• Must be:
– discernable
– distinguishable from similar
– if combined with Change, will be more likely to
be perceived, but can steal your attention
• eg: banner ad examples
Attention
• Selecting what to focus on, at a point in time,
from the range of possibilities.
• Banner ads steal attention pre-brain.
• Attention can also be in brain.
• We focus on what we think is relevant to our task.
• HOWEVER -- if didn’t make it thru senses, not a
contender.
Brain attention
• Can brain multi-task?
– No. Mostly attend to one thing at once.
• Then ...?
– Just like operating systems: Interrupt system,
context switch.
• Cost of context switch.
• Missed triggers.
• Thus, UIs should encourage this with care.
– Hands-free cells while driving? Emails while in
talks/meetings?
– Flow?
So...
• Avoid cluttered UI.
Demanding Brain’s Attention:
Interruptions
• When COMPUTER decides to call
attention to something.
• Four important kinds:
– Immediate
• For when MUST pay
immediate attention.
– Mediated
• Computer decides when to interrupt.
– Scheduled
– Negotiaated
• Best for productivity AND learning.
Attention Take-aways
(Basics for UIs)
• Users can’t attend to everything at once.
• If info does not make it thru senses,
– brain can’t attend to it.
• Once in brain:
– users attend to what they think is most
relevant. (More on this later in course.)
• User has the right to their own attention.
– There is a cost to making them switch.
– Do not steal it arbitrarily.