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

HAI2008. Lifelong ambient companions: challenges and steps to overcome them Stroop Effect From

HAI2008. Lifelong ambient companions: challenges and steps to overcome them Coding Means distinguishing different parts of an interface Includes –Font changes such as these withsize –Font with style and size –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 withsize –Font with style and size –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 withsize –Font with style and size –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 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

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 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

HAI2008. Lifelong ambient companions: challenges and steps to overcome them More examples from NASA: from 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