The role of industrial design

Human factors / ergonomics

Designing in order to optimize human well-being and overall system performance

Ergonomics (1)• Cognitive ergonomics is concerned with mental

processes, such as perception, memory, reasoning, and motor response, as they affect interactions among humans and other elements of a system.

• Physical ergonomics is concerned with human anatomical, physiological and biomechanical characteristics as they relate to physical activity.

• Organizational ergonomics is concerned with the optimization of sociotechnical systems, including their organizational structures, policies, and processes.

Female and Male Identities

Cognitive Ergonomics• Visual• Auditory• Memory

Visual (1)• The human eye has 130 million light sensitive “rods”

and 7 million color sensitive “cones” concentrated on the fovea.

• Human eye can detect about 10 million different colors. (This is why true-color is 24 bit or 224 = 16,777,216.)

• The distribution of cones is “red” cones (64%), “green” cones (32%), and “blue” cones (2%).

• The fovea has about a 2 degree angle.• We cannot make out objects at the periphery of our

vision, but we can detect motion.

Color recognition• Under ideal circumstances, humans can

identify up to 50 colors• 5 different colors for absolute accuracy• 10 different colors if minor errors are

permissible

Relative ranking of color recognitionColor Meister and

Sullivan (1969)Rizy (1967)

Red 2 1

Yellow 1 2

Magenta 4 3

White 3 4

Cyan 5 5

Blue 7 6

Green 6 7

Implications of Vision (1)• Visual acuity is how “well” we can see and image and

is perhaps the most critical implication of the eye on multimedia design.

• The eye can resolve gaps of 2mm at a distance of 2m. The visual acuity test measures the smallest letters that you can read on a standardized chart at a distance of 20 feet.

• Visual acuity increases with luminance (how much light reaches the eye) and with increased foreground/background contrast.

Implications of Vision (2)• People cannot attend to multiple images in

detail in different areas of the image at once.• Only one image should be presented at a time.• People cannot attend to moving and still images

simultaneously.• Movement at the periphery is useful for drawing

attention.

Implications of Vision (3)• People can scan an image quickly, but they

may not remember what they have just seen nor remember the details.

• Just because a person saw something does not mean that they comprehended what was seen.

• Use animation to draw attention and then a still image to focus their attention.

Minimum reaction timesModality Delay (msec)

Vision 180

Audition 140

Touch 155

Body Rotation 520

Implications of Vision (4)• Users focus on images which are

• Larger than others• More colorful or brighter (luminous)• Away from other objects• At the center of gaze• Shown in more detail• Are in focus• Near the “front” of the image

Design of visual displays (Handbook, Ch. 5.1)

• Principles• Conspicuity – sign should attract attention• Emphasis – emphasise important words or images• Legibility – contrast ratio• Intelligibility – “Fool proof”; instant, error-free

recognition (percent correct responses)• Visibility – Visible under all expected viewing

conditions• Maintainability – Display resists wear due to

sunlight, rain, cleaning, soil, etc• Standardization – Use standard words and symbols

whenever they exist

Auditory (1)• Audition

• Temporal emphasis• Verbal language• “Music”• Close to body• Omnidirectional

• Vision• Spatial (concepts)• Written• Visual arts• Distant• Directional

Auditory (2)• The human ear can hear 20Hz to 20kHz. The

“just noticeable difference” (JND) is < 1Hz at low frequencies and > 500Hz at high frequencies.

• The useable amplitude range is 100dB. The JND for amplitude is about 1dB.

Implications of Audio (1)• Sounds may provide additional cues to draw

attention or to improve recall especially when a temporal emphasis is required.

• Take care in adding audio with respect to amplitude range (discrimination).

• Do not attempt to replace written words with spoken language “just because.”

Memory (1)

Retrieval

Short Term Memory

Visual ImageStore

Auditory ImageStore

Long Term Memory

Sensory Information Store

Encoding

Maintenance

Memory (2)

Retention interval

Cor

rect

reca

ll (p

erce

nt)

1 item

3 items

5 items

>working memory

Implication of Memory (1)• Do not create competing demands for attention if you

want people to remember something from your visualization.

• People’s short-term memory is limited in time and capacity. Do not force people to remember the prior state of the visual to interpret the future state.

• Be careful not to overload memory both in terms of time of retention and amount of information to retain.

Implication of Memory (2)• Your dynamic screen changes will change

faster than the capacity of working memory to encode and store auditory and visual cues. People will only remember the “gist” of your dynamic visuals, not the details. Be careful of encoding spurious details in time varying visuals.

Implication of Memory (3)• If the comprehension of an image requires that

the user recall an item from memory, the image must remain static long enough for the memory item to be retrieved from either long-term memory or short-term memory. It takes more time to retrieve from long-term memory.

Implications of Memory (4)• How “quickly” your visual changes is then dependent

upon human cognitive capabilities including image processing by the eye and storing information into short-term memory. There is an implication that the speed of the visual perhaps should be targeted according to appropriate research based on your demographic and that the person can “go back.”

Physical Ergonomics• Alvin R. Tilley, The measure of man and

woman: human factors in design, New York: John Wiley & Sons, Inc., 2002. [620.82 112]

• Gavriel Salvendy, Handbook of human factors, New York: John Wiley & Sons, Inc., 1987. [620.82 82]

“Jack” (1)• Jack is an ergonomics and

human factors product that helps enterprises in various industries to improve the ergonomics of product designs and workplace tasks. This software enables users to position biomechanically accurate digital humans of various sizes in virtual environments, assign them tasks and analyze their performance. [http://www.ugs.com/products/efactory/jack/]

“Jack” (2)• You can make Jack various sizes.• You can assign him tasks and analyze his

performance.• Jack can tell you what he can see and reach.• Jack can tell you if he’s comfortable, if he got

hurt, and when you exceed his strength.

“Standard” Men: 1 percentile man

“Standard” Women: 1 percentile

Hand Data (Tilley, p. 42)

Disabled Data (Tilley, p.19)

Measures• human error probability

(HEP)• Error rate increases

• x2 for low stress (not paying attention)

• x1 for optimal stress (paying attention / focus)

• x2 for moderate stress for skilled people, x4 for novices

• x5 for high stress for skilled, x10 for novices

errorfor iesopportunit ofnumber errors ofnumber

HEP

Summary• Critical to test a design with actual people.• Ergonomic data and computational human

modeling software tools provide the means to create digital mockups for initial testing.

• Follow simulation with real-world verification.• Engineering and design uses of animation,

modeling and agent simulations.