Cognitive and physiological design drivers Judy Kay CHAI: Computer human adapted interaction research group School of Information Technologies

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


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


Stroop Effect

From http://faculty.washington.edu/chudler/words.html


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 ...


Coding

• Means distinguishing different parts of an interface• Includes




– Sound

– Movement

• All are about ... gaining attention


Colour can be poorly used• Means distinguishing different parts of an interface• Includes




– Sound

– Movement

• All are about ... gaining attention


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


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


• 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


• 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?


Light text on a dark background

Dark text on a light background


Red text on a dark background

Red text on a light background


Red text seems to focus differently


Red text seems to focus differentlyRed text seems to focus differently











So many ways to make mistakes...

Guidelines

eg http://colorusage.arc.nasa.gov/guidelines.php


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.


• http://colorusage.arc.nasa.gov/assets/blue_1.gif


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


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


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


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


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


Shapes

• Conventions for some shapes– eg warning and errors

• Special shapes– eg little hand pointing

• Cultural boundaries


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

Documents

Cognitive and physiological design drivers Judy Kay CHAI: Computer human adapted interaction research group School of Information Technologies