CEN3722 Human Computer Interaction Displays Dr. Ron Eaglin

Objectives Describe the following display principles Perceptual operations Mental models Attention Memory Describe principles behind alerting displays, including: Warnings Cautions Advisories Describe principles underlying appropriate labeling

Objectives Describe the following display principles Pictorial realism Moving part Redundancy gain Discriminability Proximity compatibility Predictive aiding Knowledge in the world Consistency

Displays Human made artifacts designed to support the perception of relevant systems variables and facilitate processing of that information Visual Graphs Speedometer Gauges Print Auditory Buzzers Beeps

Display Variables Location Color Dimensionality Motion Intensity Coding Modality What to display

Display - Example 23.445 98 23.11 4 12 1245

Display Example 23.445 98 23.11 4 12 1245

Display Principles Perceptual operations Mental model Human attention Human memory

Perceptual Principles Avoid absolute judgment limits Do not require operator to judge the level of a variable on the basis of a single sensory variable like color, size, or loudness, with numerous levels. IF light is royal blue, THEN all systems are GO

Perceptual Principles Top-down processing Users perceive and interpret signals in accordance with what they expect to perceive on the basis of past experience Valve 12 is OK Valve 13 is OK Valve 14 is OK Valve 15 is OFF Valve 16 is OK Valve 12 is OK Valve 13 is OK Valve 14 is OK Valve 15 is OFF Valve 16 is OK

Perceptual Principles Redundancy Gain Messages expressed multiple times are more likely to be interpreted correctly. Best if multiple messages are in alternative forms (e.g., visual AND aural channels). WARNING WARNING Color Only Color + Label Color + Label + Auditory

Perceptual Principles

Perceptual Principles Discriminability: Similarity causes confusion Signals that are similar will be confused Either at time they are perceived or if signals must be kept in working memory Similarity affected by ratio of similar to dissimilar features: J606V45 versus J706V45 5 similar, 1 dissimilar 606 versus 706 2 similar, 1 dissimilar

Perceptual Principles This figure illustrates how the growth of large companies has increased over the last few years. This figure illustrates how the growth of large countries has increased over the last few years.

Perceptual Principles Companies Countries This figure illustrates how the growth of large companies has increased over the last few years. This figure illustrates how the growth of large countries has increased over the last few years.

Mental Model Principles Principle of Pictorial Realism (Display should look like variable it represents) 100 ° 100 ° ° °

Mental Model Principles Principle of the Moving Part - Moving elements of any display of dynamic information should move in a spatial pattern and direction that is compatible with the user’s mental model of how the represented element moves. (follow user mental model) 375 400 425 450 475 500 430 525 465 500 525 475 500 450 475 400 465 425 450 400 425 375 400

Mental Model Principle Ecological Interface Design Use principles of pictorial realism and moving part to create display with close correspondence with real world system Consistent with/create operator mental model

Mental Model Principles Time 1 Time 2 340 260 110 Reservoir : 340 Reservoir : 330 Holding: 260 Holding: 270 Valve Open Flow:110 p/m Reservoir Flow: 0 p/m Holding Area Valve: Open Valve: Closed 330 270 Pictorial Realism Moving Part Redundancy Gain Valve Closed Reservoir Holding Area

Attention Principles Minimizing information access cost - There is a mental cost associated with the time or effort to move selective attention from one display location to another to access information Good designs minimize cost by keeping frequently accessed information sources in a prominent place

Attention Principles Proximity compatibility principle When two or more sources of information are related, and must be mentally integrated to complete a task (through divided attention), then they should be placed contiguously in space “Close mental proximity” requires “close display proximity”

Attention Principles Focused attention Divided attention Allows information sources to be perceived without distraction from other information sources Divided attention Allows parallel processing of two or more information sources Selective attention Attention shifts based on salience of incoming information.

Proximity Compatibility Principle

Attention Principles + Principle of multiple information resources Processing a large amount of information can be facilitated by dividing information into multiple channels Visual + Visual Audio

Memory Principles Principle of predictive aiding Predicting future is hard Current conditions Possible future conditions Rules that map (relate) the two As a result, human operators become reactive rather than proactive React to events after the fact versus anticipating events. Replace “current status” display with predictive display Allows operators to rely on perceptual versus cognitive processing

Memory Principles Principle of knowledge in the world Information prominently displayed Recognition versus recall: Visibility Knowledge in the head requires relying on retrieval from long term memory Graphical user interface versus command line

Memory Principles Principle of consistency Display information consistently Across multiple displays/windows/screens. Make behavior consistent Exit shortcut: Exit versus Exit

Alerting Displays System alerts differ by criticality Severity of the consequences for ignoring them Warnings Most critical Use auditory AND visual alert

Alerting Displays Cautions Same as warning, use both auditory and visual signal Less salient auditory signal (“softer” sound)

Alerting Displays Advisories Least critical Need not include auditory signal (only visual)

Labels Used to unambiguously identify elements Present “knowledge in the world

Label Design Principles Visibility/legibility Contrast sensitivity a concern Contrast sufficient so that label can be read in poorest of conditions

Label design Principles Discriminability Operator should be able to clearly discriminate between labels Relates to distinct features

Label Design Principles Discriminability Tendency to confuse negative and positive labels Problem under degraded sensory conditions Low visibility for visual indicators Noisy environments for auditory warnings

Labels Meaningfulness No guarantee that a particular word or icon triggers the appropriate meaning, even if it is visible and legible. Avoid labels based solely on icons or abbreviations

Objectives Describe the following display principles Perceptual operations Mental models Attention Memory Describe principles behind alerting displays, including: Warnings Cautions Advisories Describe principles underlying appropriate labeling

Objectives Describe the following display principles Pictorial realism Moving part Redundancy gain Discriminability Proximity compatibility Predictive aiding Knowledge in the world Consistency