Cognitive and physiological design drivers
Judy Kay
CHAI: Computer human adapted interaction research group
School of Information Technologies
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Overview
• Thinking about people
• Cognitive constraints
• Physical constraints
• Physiological constraints
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Postconditions for this week
• Identify human constraints that are important for design and evaluation of pervasive systems– Cognitive
– Physical
– Physiological
• For a particular design for a pervasive interface, explain how these may be important
• Explain how to refine a proposed to design to take account of these factors
• Identify such issues particular to pervasive computing
Stroop effect
http://faculty.washington.edu/chudler/java/ready.html
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Stroop Effect
From http://faculty.washington.edu/chudler/words.html
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Coding
• Means distinguishing different parts of an interface• Includes
– Font changes such as these
– Font withwith style and sizesize– Use of colour such as here and here – seriously
– Special symbols, shapes
– Sound
– Movement
• All are about ...
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Coding
• Means distinguishing different parts of an interface• Includes
– Font changes such as these
– Font withwith style and sizesize– Use of colour such as here and here – seriously
– Special symbols, shapes
– Sound
– Movement
• All are about ... gaining attention
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Colour can be poorly used• Means distinguishing different parts of an interface• Includes
– Font changes such as these
– Font withwith style and sizesize– Use of colour such as here and here – seriously
– Special symbols, shapes
– Sound
– Movement
• All are about ... gaining attention
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Colour
• Properties– Hue – wavelength (red .. violet)
– Saturation, chroma (purity, mix of wavelengths)• High saturation very pure
• Low saturation, greyish
– Brightness, intensity, value • very low intensity becomes black
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Physiology and colour
• Rods and cones• Fovea – detailed vision (eg text)• Only cones sensitive to colour
– 64% respond to red
– 32% to green
– 2% to blue (none in fovea!)
• Opposing colours at the neuron level– Red-green, yellow-blue
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
• Visual acuity reduced for violet end of spectrum• Insensitivity to blue increases with age• Blue seems harder to read, especially on some
backgrounds• With normal light, we see mid-spectrum colours
vesr (ie green, yellow)• Colour blindness
– 8% men, 0.4% women
– Use additional redundant cue eg colour + box + brightness difference and this improves broad performance
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
• Reds appear closer than blues• Warm colours appear larger than cool colours
– eg red larger than blue
• Blooming effect– Light colours on dark backgrounds appear larger
• Colours distant on spectrum require refocusing• After images and shadows can follow
– Opposing colours
– Highly saturated colours
• Illumination matters too - pervasive?
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Light text on a dark background
Dark text on a light background
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Red text on a dark background
Red text on a light background
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Red text seems to focus differently
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Red text seems to focus differentlyRed text seems to focus differently
Red text seems to focus differently
Red text seems to focus differently
Red text seems to focus differently
Red text seems to focus differently
Red text seems to focus differently
Red text seems to focus differently
Red text seems to focus differently
Red text seems to focus differently
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
So many ways to make mistakes...
Guidelines
eg http://colorusage.arc.nasa.gov/guidelines.php
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Examples:
• Pure blue shall not be used on a dark background for text, thin lines, or high resolution information. [Source: DOE-HFAC 1, 1992] FAA Human Factors Design Standard, p 8-58
• 8.6.2.2.7 Blue. Blue should not be used as the foreground color if resolution of fine details is required. [Source: DOD HCISG V2.0, 1992] FAA Human Factors Design Standard, p 8-57.
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
• http://colorusage.arc.nasa.gov/assets/blue_1.gif
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
More examples from NASA:from http://colorusage.arc.nasa.gov/guidelines_discrim_id.php
• Use no more than six colors to label graphic elements.
• Use colors in conformity with cultural conventions.• Use color coding consistently across displays and
pages• Use color coding redundantly with other graphic
dimensions. • Don't use color coding on small graphic elements
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Recommendations
• Use colour sparingly• Maximum codings 5 (+ or – 2) matching short term
memory• Design in monochrome first• Optimise all other aspects of design and layout• Add colour (with awareness of problems)• Use colour to:
– Draw attention (better than shape, size, brightness)
– Show organisation, status, relationships
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
cont
• With black foreground, use cyan, magenta, white• Ensure contrast ib hue and brightness of fore- and
background
• Allow users to control colour coding• Use colour consistently across system• Use other (redundant) cues as well• Avoid saturated blue for small text and thin lines
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Blinking and movement
When is it good?
And not?
Take yourself back to hunter and gatherer times:
A hungry tiger is coming from the distance at your right
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Blinking and movement
• Hard to ignore• Reduces legibility• Can be really annoying
• Helpful for tiny cursors (otherwise hard to find and large ones are obtrusive)
• Helpful for critical situations
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Shapes
• Conventions for some shapes– eg warning and errors
• Special shapes– eg little hand pointing
• Cultural boundaries
HAI2008.Lifelong ambient companions: challenges and steps to overcome them
Summary
• Awareness of constraints on design of pervasive computing interfaces because of human constraints
• Ignoring them can create systems that nobody can use effectively
• Next week personalisation
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