Displays Chapter 8 Rebecca W. Boren, Ph.D. Introduction to Human Factors Engineering IEE 437/547 Arizona State University October 17, 2011

What are displays? Human-made artifacts designed to support the perception of relevant system variables and further processing of that information.

Ways of Classifying Displays Physical properties The tasks they are designed to support Properties of the human user that dictate the best mapping between display and task (what we learned from the chapters on vision, hearing, and cognition)

Ways of Classifying Displays Physical properties: Color or monochrome Visual or auditory modality 3-D display or stereo

Ways of Classifying Displays The tasks they are designed to support: Navigating Controlling Decision Making Learning So forth…

Ways of Classifying Displays Properties of the human user that dictate the best mapping between display and task: Thirteen principles of display design Perceptual principles Mental model principles Principles based on attention Memory Principles

Perceptual Principles Display Principles Perceptual Principles

Make displays legible (or audible) Good contrast Font size and type How far away will the display be viewed? Use the principles for vision (ch 4) and audition (ch 5) Example: ClearviewHwy Fonts

Avoid absolute judgment Do not require users to judge the level of a variable on the basis of a single sensor variable like color or size, which contains more than five to seven possible levels.

The variables used to differentiate the batteries are their size and form.

What variable is used to differentiate these screwdrivers?

What variable is used to differentiate these screwdrivers? Answer: Length Does it conform to the Principle of Avoiding Absolute Judgment?

Choose a leather

How many colors are used in this example?

Does this conform to the Principle of Avoiding Absolute Judgment? Answer: 3 Does this conform to the Principle of Avoiding Absolute Judgment?

Unnatural mapping Natural mapping

Top-down processing People will perceive and interpret signals in accordance with what they expect to perceive on the basis of past experience. WARNING

Can you identify these signs by their shape?

Were you correct?

Redundancy gain When the same message is expressed more than once, particularly if the presentation is in alternative physical forms. (In this case, color and words.)

Discriminability Similarity causes confusion

Discriminability Similarity causes confusion

Problem With the design on the left, the two displays are very similar, but represent two very different quantities. Both displays have the same numeric scale with the same incremental increases. This can cause driver confusion. Bad Good Solution To eliminate confusion, the tachometer and speedometer should be on different numeric scales, like the display on the right.

Mental Model Principles Display Principles Mental Model Principles

Principle of pictorial realism A display should look like the variable that it represents. X X X X

Quicken Check-writing Features – looks like an actual checkbook.

Principle of the moving part Display variables move similarly to the way the actual parts move.

Principle of the moving part Safety Blanket Uses 4 AA batteries and car plug 4 lighting modes: arrows flashing in sequence, all arrows flashing simultaneously, all arrows on at the same time, reflectors only (lights off) http://www.astrooptics.com/emergency.html

Principles Based on Attention Display Principles Principles Based on Attention

Minimizing information access cost Cost is measured in time and effort of the user. Keep frequently accessed sources in such a location that the cost of traveling between them is small.

Drop-down Menus

Proximity compatibility principle Sometimes two or more sources of information must be mentally integrated to complete the task. Parts of the information should be close together, but not too close.

Proximity compatibility principle and (c) are better than (b) or (d)

Proximity compatibility principle

Principle of multiple resources Dividing information display between modalities (audition and vision). Multiple cues to identification. Icons accompanied by words.

Display Principles Memory Principles

Replace memory with visual information: Knowledge in the World Visible reminders or statements of what is to be done. Computer on the right with labels For each device: E:, A:, D:, F:, G:.

Principle of predictive aiding Help with making prediction in the future.

Principle of consistency When all else fails, standardize.

Confusing Signs

Confusing Signs

Confusing Signs

Let’s look at this example of a home office. Any Questions so far? Let’s look at this example of a home office.

What display principles can we apply here?

Why is this better?

What is the best way to present an alert? Alerting Displays What is the best way to present an alert?

Alerting Displays Should it be visual or auditory? Could it be both?

Alerting Displays Three levels of alerts Warning: most critical category; signaled by the most salient auditory alerts. Cautions: less critical, softer auditory alert. Advisories: need not be auditory. Can be visual.

Alerting Displays Smoke alarm Radar detector Warning light

Alerting Displays Aviation community has agreed on a common color code: Red for warning Amber or yellow for caution Other colors (that cannot be confused with red or amber) for advisory information.

Display that is static and unchanging. Labels Display that is static and unchanging.

Labels Purpose is to signal the identity or function of an entity. Represents “knowledge in the world” Usually print, but can be an icon.

Design criteria for labels: Visibility/legibility (contrast sensitivity) Discriminability (try to avoid Don’t) Meaningfulness (avoid icons only or abbreviations) Location (should be located physically close to the entity)

Monitoring Displays Potentially changing values, such as noise level, speed, temperature, etc.

Design criteria for monitoring displays Legibility Analog versus digital If analog is chosen, the orientation of the display scale should be in a form and direction that is congruent with the user’s mental model. Up or right shows increase.

Prediction Prediction is not something humans do very well, particularly under stress. A good predictor display can aid human performance. Do not try to predict further into the future than is reasonable and necessary. Sluggishness can be a problem.

Multiple Displays Establish a primary visual area (PVA)

Multiple Monitors http://www.codinghorror.com/blog/2007/08/the-large-display-paradox.html

The Large Display Paradox Is a large display more productive or not?

Design criteria for multiple display layouts Frequency of use. Most frequently used displays should be adjacent to the PVA. Display relatedness or sequence of use.

Navigation Displays serve to Provide guidance about how to get to a destination. Facilitate planning Help recovery if the traveler becomes lost. Maintain situation awareness regarding the location of a broad range of objects.

Forms of navigation displays Paper Electronic

Navigation may be through Physical space, or Information space

Navigation Displays & Maps Route lists & command displays work best if accompanied by a map.

Electronic Maps With electronic maps, detail can be achieved without sacrificing legibility if zooming capabilities are incorporated.

The Problem with Clutter Clutter slows down the time to access information Slows down the time to read items, as a consequence of masking by nearby items.

Cluttered Map

Solutions to the Problem of Clutter Effective color-coding Minimalist maps With electronic maps it is possible to highlight needed information A “you are here” or YAH indication is useful

Solutions to the Problem of Clutter Minimalist Maps You Are Here Maps

Tables & Graphs Decide how best to display data Legibility and clutter are issues. “Greatest amount of data with the least amount of ink”

Other Display Modes The most common forms of display are visual and auditory. Occasionally, touch and smell are used to alert us.

Olfactory Displays Olfactory relates to the sense of smell. Natural gas does not have any odor. A stinky smell is added to warn of a gas leak.

IF THE RED LIGHT IS BLINKING OR YOU SMELL WINTERGREEN – EVACUATE THE BUILDING In buildings where carbon dioxide is released when a fire is detected, an odor of wintergreen was added to the gas as a warning. E. J. McCormick & M. S. Sanders, Human Factors in Engineering and Design, 5th Ed., 1982, p. 150.

Tactile Displays Bott’s Dots are used on the highway to mark the lanes. They are also used on the race track to help the drivers stay on course.

Any Questions?

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