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I begin a PhD program in Human Factors on August 30th.  I thought it was a perfect time to spruce up my blog and make some changes online.  It was also time for me to put on my programming hat and teach myself a thing or two about web design.

I asked all of you for your input on my new domain name. You responded with priceless suggestions and opinions.  Finally I went with my gut and made a decision.  The Tao of Grad School is here to stay, but I’m moving to a happier place.  Please be patient because the layout is still a work in progress.

So head over to my blog (and subscribe if you feel so inclined)! From here on out, I will be blogging here:

This post is part of my Human Factors series.  I am very interested in the design of unmanned or autonomous systems. OK, you got me.  I just really love robots and also want to be as prepared as possible when The Singularity finally approaches.  #nerdalert  Today I’d like to discuss one of the major disadvantages of automation, reduced operator situation awareness. I will also briefly showcase research outlining ways to design around this disadvantage.

{image via Alexandr Zudin}

Autonomous, semi-autonomous, and remotely operated vehicles each introduce their own issues in operator workload, building or recovering situation awareness, and sustaining attention.  Human factors engineering is especially important when the cost of attrition of systems and human lives is high in certain military operations (Essens, 2001).  Some Human Factors research attempts to apply our understanding of a human’s cognitive and physical abilities and limitations to automated (i.e., unmanned, autonomous, remotely operated) systems.  I say “attempt” because it is often difficult to design the best system under financial constraints and political tensions.  It is rare to see Human Factors engineering implemented correctly during the initial design process.

Automated systems come with a multitude of issues that piloted systems do not have.  We are still learning how to design such interfaces.  There is currently no such thing as a purely unmanned system.  Terminators won’t exist until 2029, remember?  For now, an operator is required to at least turn on a system, operate it remotely or monitor its actions.  Automated systems too often are designed without the human operator in mind.

What is automation?

Automation is “the full or partial replacement of a function previously carried out by the human operator” (Parasuraman, Sheridan & Wickens, 2000, p. 286). In general, automation is the replacement of human functioning by machine functioning (Parsons, 1985; Satchell, 1993; Wiener, 1988).  It involves substituting automation components for tasks humans are either capable or incapable of performing themselves.  Automation may be used to perform functions humans cannot perform due to basic limitations such as complex mathematical calculations, to perform functions humans perform poorly or with increased workload, to assist or supplement human performance, or if is too expensive or dangerous to use human operators (Wickens, 1992; Wickens & Hollands, 2000).  Despite these advantages of automation, it is important to consider the implications of automation on human performance (Hancock, 1996).

The question is no longer whether one or another function can be automated, but, rather, whether it should be.– Wiener & Curry (1980)

Disadvantages of automation

For a full review see Wickens & Hollands (2003) and Scerbo (1996).

Situation awareness

An important drawback to automation is a decrease in an operator’s situation awareness of their work environment, which can be detrimental to decision-making.  Humans may be less aware of changes in the environment or system states when those changes are under the control of automation than when they make changes themselves. Situation awareness (SA) refers to the cognitive processes leading to decisions regarding likely future events in a particular environment.

Situation awareness involves (Endsley, Hansman, & Farley, 1999):

  • Perceiving the elements in a particular environment
  • Understanding the meaning of those elements
  • Translating the perception and understanding of the environment into a schema of likely future events.

According to Endsley (2003), many human errors attributed to poor decision-making involve problems with the SA aspect of the decision-making process. People make decisions based on their perceptions of the situation.  During command and control operations the decision maker is forced to establish an ongoing awareness and understanding of the situation. Situation awareness provides the primary input to the decision process and plays a significant role in determining which course of action is selected.

Endsley's SA model (2003)

SA and automation

Wickens, Parasuraman, and Sheridan (2000) established a model for the types and levels of human interaction with automation.  Automation can vary across a continuum of levels from fully manual (low level of automation) to fully autonomous (high level of automation).  These levels of automation have been described in detail in the literature and range from a simple, dual mode of automation to ten levels of automation in complex systems (AGARD, 1986; Billings, 1991; Riley, 1989; Rouse & Rouse, 1983; Sheridan, 1978; Parasuraman et al., 2000; Scerbo, 1996).

Intermediate levels of automation are those where one or more human operators control and coordinate the efforts of multiple autonomous systems. At the intermediate level are autonomous manned and autonomous unmanned operations.  During autonomous manned operation all work is done automatically, but the operator is present on the vehicle, monitoring the system and ensuring proper execution of operations.  During autonomous unmanned operation, there is no operator on the vehicle itself, but an operator is monitoring, navigating, launching and/or recovering the autonomous vehicle. Scripted autonomous systems use pre-programmed scripts to accomplish intended mission objectives and have no interaction with humans after they are deployed.  Supervised autonomous systems automate some or all of the functions of planning, sensing, monitoring, and networking to carry out autonomous activities and use the human operator’s cognitive abilities to make decisions, perceive the meaning of sensor data, diagnose problems, and collaborate with other systems.

Parasuraman, Sheridan and Wickens (2000) extended Sheridan and Verplank’s (1978) levels of automation to describe four stages of information processing within which each level of automation may exist: information acquisition, information analysis, decision/action selection, and action implementation. For example, unmanned surface vehicles are fully autonomous at the first three levels of information processing and currently do not execute forms of action on their own.  In other words, weapons release authority is still under the control of a human operator (remember, no Terminators).

If this is something that interests you, I highly recommend reading the full article.

Four levels of automation:

  1. Information Acquisition. The first stage involves the acquisition, registration, and position of multiple information sources similar to that of humans’ initial sensory processing.
  2. Information Analysis.  The second stage refers to conscious perception, selective attention, cognition, and the manipulation of processed information such as in the Baddeley model of information processing (Baddeley, 1996; Parasuraman et al., 2000; Wickens & Hollands, 2000).
  3. Decision and Action Selection Next, automation can make decisions based on information acquisition, analysis and integration.
  4. Action Implementation. Finally, automation may execute forms of action.

Parasuraman and Byrne (2003) explain that the impact of automation on SA depends on both the type and level of automation.  Automation at the information acquisition level yields evidence of improved SA (Wickens, 2003).  At the decision making stage, it is thought that in high-risk settings decision automation should be at a lower level of automation so the operator may be “in-the-loop” during the decision-making process (Wickens et al., 1998).  There are cases when automation should be set to a higher level, such as when operators are under time pressure and must make rapid decisions (Parasuraman, 2008).  Wickens (1994) showed that humans are less aware of their surroundings when another agent (e.g., another human or automation), makes system changes in contrast with times in which when they make the changes themselves.

Parasuraman, Sheridan & Wickens (2000), p. 288

———-

Dr. Raja Parasuraman is a professor at George Mason University. Dr. Christopher Wickens was a professor Emeritus at University of Illinois Urbana-Champaign and now works at Alion Science and Technology. Dr. Mark Scerbo is a professor at Old Dominion University.  Yes, he is one of my professors.  Dr. Mica Endsley is the owner of SA Technologies, Inc. All of these scientists are leaders in the field of Human Factors, especially with regard to automation.  You might even say, they are Human Factors rock stars.

My mom has a Master’s in Journalism.  She was a radio DJ and a local news reporter before she married a soldier and gave birth to me.  Eventually her writing talent paved the way to a career as an editor and photojournalist.  Photography became part of her day-to-day job over the last 10 years and soon she took that skill home with her.  She takes hundreds of pictures every month because she loves it (almost as much as gardening).  When she retires, I am going to help her start a photo blog so she can share her passion with others.  You can find some of her photos on Flickr.

While I was in Huntsville, my family had to set up for an Open House.  My mom bought a few little sunflowers to spruce up her kitchen.  One afternoon, she walked by the table, stopped, turned around and picked up her camera. Sunlight from the skylight in the kitchen beamed down on the flowers, making shadows on the table.

I believe my mom is an incredibly talented photographer because she sees beauty in every day moments that most of us would never notice.

She sees such beauty in every day life because her eyes are always open.

When was the last time you stopped and really noticed the beauty of the moment?

~~~~~

I wrote this post on Monday and scheduled it for today.  I think it’s neat how timing works out sometimes.  This week Doni, Rachel, Lacey and Michelle launched a new photo blog to capture the “beauty in every day life.” Check out Project 4/365: 4 Girls, 365 Days.

Here’s a shout out to some fabulous photographers: Chris, Chrissy, Ashley, Kyla, Anne, Elizabeth, Erin, Martin and Sebastian.

I recommend bookmarking or subscribing to National Geographic photography, PictoryMag.com, Mother Jones Photo Essays and The Big Picture.

I’d love to list all my favorite photographers who are famous, but that would take too long!

Zen and the art of stuff

Ending materialism doesn’t mean forsaking all your possessions. Ridding yourself of everything you own would only prove you are still too preoccupied with possessions themselves. Someone who has developed a healthy inner world would see possessions as neutral. This shift is more about attitude than specific actions. ~ Scott H Young

Growing up, I moved every few years because my dad was in the military.  Each time we moved, we had a big moving sale.  While over time I slowly purged most of my old things, I always felt it was important to hold on to certain things from my past. This weekend I helped my mom clean out my old room before she moves.  When I moved to Virginia Beach two years ago, I knew I didn’t have room for all my belongings.  I boxed up everything I couldn’t use at the time and my mom stored all of it in my old closet.

I’ve mentioned before on my blog that I moved six times between 2000 and 2008.  I was never one to stay in one place very long.  Now that I am in a good place in life and love my location, I plan to move into a new place and stay as long as possible.  This new space requires some major downsizing on my part.  It’s time to simplify on a whole new level.

Minimalism vs. Materialism

My Google Reader is filled with great posts about Minimalism. It is a huge movement in our generation.  Rightly so.  Sometimes we become attached to stuff and we allow the stuff to control us. As Chuck Palahniuk wrote in Fight Club: “[…] you’re trapped in your lovely nest, and the things that you used to own, now they own you.”  I think some of us see our friends and family struggle with needless debt while they keep up with the Joneses and we don’t want to be there in ten years. Sometimes we also hold on to old things because we do not want to let go of the past. We grip tightly to that book or toy or outfit or whatever it is because we cannot allow ourselves to move on.

As I get older, my values change and evolve. What I valued at 10 is not at all what I value at 27; therefore, the things I value now are not the things I valued at 10.  I am also a Pisces.  I am sentimental sometimes to a fault.  I sometimes feel that when I let go of the thing, I will leave part of myself behind. I know memory is often fallible. I feel if I give away a gift from a friend of family member, I will forget those memories created around the object. I will no longer have a salient cue to remind me of those experiences I had with those people who are so important to me.

I believe moving from one end of a spectrum to the opposite side of the spectrum can become a form of attachment in and of itself because we become obsessed with the idea of not being, doing or owning something. So how can we find the middle ground between Material and Minimalism? I don’t think I will ever be a pure minimalist for various personal reasons.  I do know I have to look inward, reflect and ask myself, “What do I keep and why do I keep it?”

How I simplified and still kept my Pottery Barn dishes

Barrie Davenport from Love Bold and Bloom wrote an excellent guest post on this topic at Zen Habits: How to Simplify When You Love Your Stuff. She says to consider some “parameters” when thinking about things and to ask yourself if:

  • It brings beauty into your life and stirs your soul.
  • It supports a passion or hobby.
  • It helps bring family and friends together in a creative, meaningful way.
  • It educates and enlightens.
  • It makes life profoundly simpler so that you can pursue more meaningful things.
  • It helps someone who is sick or incapacitated.
  • It is useful and necessary for day-to-day life.
  • It’s part of a meaningful tradition or a reminder of a special event.

Spot. On.  Thinking about my belongings in the context of those parameters makes perfect sense to me.  After some deep breathes, tears, smiles, laughs and long talks with my mom, I decided to keep about 1/4 of the stuff in that old room.

  • I kept my nice Pottery Barn dishes because I will use them for the dinner parties I plan to host in the future with my friends and family.
  • I kept a set of gorgeous pottery someone very special to me brought back from Japan.
  • I kept some of my old books I cannot imagine leaving behind yet.  Most of these books were gifts from loved ones.  Each book represents how much I value relationships, education, learning and growth of mind, body and spirit.
  • I kept a small box of love letters, cards and notes I’ve collected since 1997.  They stir my soul and will always be beautiful reminders of the incredible love in my life.  An old card from my grandmother saying she is proud of me, a letter from my Dad signed with Love when I was in middle school, five handwritten pages from my mother before I went to college and a love letter from someone I almost married are worth more than gold.
  • I kept this Mr. Punch poster that Neil Gaiman and Dave McKean autographed.  It is a beautiful piece of art to me because Neil Gaiman is my favorite writer, Dave McKean is one of my favorite artists and The Tragical Comedy or Comical Tragedy of Mr. Punch was one of the first graphic novels I loved as a teenager.
  • I also picked out a few stuffed animals that carry with them cherished memories of times with my family and friends.

The rest of my things are going in a yard sale, on ebay, to a shelter for victims of domestic violence, to the library and to the local fire station.*

It feels good to know more about what I value as an adult.  It feels good to leave certain aspects of the past behind me.  It feels even better knowing my mom only has five boxes to move from that room instead of twenty.  I know I need to let go of certain things so I can move on.  It is OK to have stuff when I understand why I have that stuff.  I can hold on to a thing that makes my soul shine a little brighter, when it makes me smile, when I can share it with my friends and family or when it reminds me of the most important people in my life.

It’s all about balance and introspection, isn’t it?  It’s all about Zen and the art of everything.

~~~~~

Not sure what to do with your old toys?  Call your local police department, fire department, domestic violence shelter and children’s hospital to see if they accept toy donations.  You never know when a child or teenager might end up in a tough situation without something to comfort him.  You can also check out these great charities: Project Night Night and Stuffed Animals for Emergencies (SAFE).  And a quick tip: Your kids aren’t going to want your toys from the 80s.  Have you seen the bad ass toys kids have now?  Right.  I promise your Barbies will be happier if they end up in the hands of a child who just lost all her things in a fire and your own child will be happier with a newer, more anatomically correct Barbie.

This weekend I went through my old closet and found these gems (among others).  Holy retro flashbacks, Batman!

My mom's Midge doll (Barbie's BFF) - 1964

circa 1989

1989

Got this Flounder on my first family trip to Disney World when I was 6 years old

Most of my time lately is spent collecting and analyzing thesis data, working, prepping for classes next semester, taking care of my grandfather and getting ready to move.  There just aren’t enough hours in the day to do everything and be everything.  Things can get overwhelming with work and school and life that we can forget to make time for the people and things that are most important to us.  So sometimes we just have step back and make time for the important stuff.          

I flew into Huntsville, Alabama Wednesday night around midnight.  I haven’t mentioned that I was going to be in Alabama because it was a secret. Secrets are so fun!       

I am in town because my mom is moving and some of my belongings are still in her house.  I need to donate, pack, ship, or sell my old stuff. I need to decide if I want any of the furniture in the house.  There is no reason for her to move something unless she absolutely has to move it.         

 I am also in town so I can see my little brother who just turned 19.  (What the?!)  I wish he lived closer so I could see him more often.   But mostly…   I’m here to surprise my BFF!      

       

Michelle and Chris are expecting their first baby very soon.  They are my oldest, best friends in the world.  I moved around so much as a kid that I am not one of those people who has a friend from kindergarten.  I met Chris and Michelle in high school and our friendship has evolved over time.  Even though we live very separate lives and are moving along very different life paths, I think we have that kind of friendship that will last a lifetime.            

I am so through-the-roof ecstatically happy for them to bring this new life into the world together! 

 There is a baby shower on Saturday.  I missed the first baby shower because I was out of the country for work.  I wanted to see Chris and Michelle this summer before the baby was born, but I was not sure if I could pull off a last-minute trip to Alabama for various reasons (e.g., timing and money).  When I figured out a way to make this trip happen, I thought it would be fun to surprise her!   I told Chris, so we could coordinate getting together before the shower.  So, she had no idea I was coming.  When Michelle found out she had to be on bed rest because of some potential health issues, I was even happier I would be in town to see her for a few days. 

Michelle and Chris at Voodoo Fest - photo credit: Catchy Photography

 Chris and Michelle will be amazing parents because they are wonderful children, grand-children, siblings and friends. They are resilient, kind, funny and so damn smart. Michelle will be an incredibly nurturing caretaker and wise teacher in every stage of their child’s life.  I already know Chris will be one of those cool dads everyone wishes they had growing up, but I also know he will be fair and firm.   If I ever decide to have children, I hope they can know these two people like I know them.  And I mean, let’s just get it out on the table: The kid’s going to be insanely good-looking, too.  I cannot wait to meet their baby.  I also cannot wait for their relationship to grow even stronger with this new addition to their family. 

 Namasté, Chris and Michelle!

~~~~~

“True friendship isn’t about being there when it’s convenient; it’s about being there when it’s not.”

     

Welcome back to my Human Factors series. Last month I talked a little about the basics of usability testing.  This month I thought I’d discuss some basic principles of interface design.

Image via Jared Donovan

HCI: Human-Computer interaction

Human-Computer Interaction is a major area of study within Human Factors.  To design appropriate computer systems for humans, designers must understand the complexities and limitations of human perception and cognition.  There are numerous issues within human-computer interaction.  One HCI issue of particular interest to me is interface design.  If you would like to read more about HCI, I highly recommend browsing this epic list of HCI texts.

How can psychologists contribute to interface design? The brain is an incredibly complex, sophisticated organ.  Scientists learn more every day about human sensation, perception, information processing, learning, working memory, long-term memory, language, problem solving, etc.  Human factors psychologists and engineers can design guidelines for systems using their knowledge of strengths and weaknesses of the human brain.  Psychological theories can aid in the development of models of behavior (e.g., to predict physical activity and problem solving with a system).  Psychology offers empirically based evaluative and analytic techniques to assess both the human and computer in the interaction (Fix, Finlay, Abowd & Beale, 2003).

Interface design is not always intuitive or “common sense.” It is important that designers not use personal preference as a baseline for usability.  Unfortunately, humans do not always intuitively know what makes them faster, more efficient or more accurate.  Preference does not equal performance.  We could type 10-15 % faster with fewer errors if we changed from a QWERTY to a DVORAK keyboard, but we accept QWERTY as a standard in our culture (Mayhew, 1992).  Don’t worry, I won’t get into Fitts’s law or Guiard’s model of bimanual skill.  My (very general and brief) discussion is limited to visual principles of interface design.  Other principles apply to the other sensory systems like touch and audition. I also will not address individual differences, input devices or ergonomics.  One post cannot begin to highlight everything involved in creating a great interface.

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General Static Display Principles

Image via Alex Faaborg

Gestalt Display Principles

Principle of Information Need. Operators should only be presented with the information they need to complete mission objectives.

Principle of Legibility. Display size should be large enough so details can always be resolved.  Contrast and brightness should be adequate for any type of lighting and glare situation.

Proximity-Compatibility Principle. Commonly used or related information and instruments should be close together to reduce scanning and processing time and cognitive burden.

Principle of Pictorial Realism. Displays should look like the information that it represents.  The display should look like the information that it represents.  It should be realistic, representative of the real world and match the user’s mental model.  Heat can be represented by sunshine or fire based on meaning.  A thermometer can represent temperature. Prior experience and knowledge often dictates how we process information.  A t-shirt may represent heat and a coat may represent cold based on our experience with those concepts.  Concrete concepts are easy to process.  Abstract concepts are not easy to process.  Cultural differences play a role here because what is concrete in one country may be abstract to another.

Principle of the Moving Part. The portion of the display that moves should correspond to that element of the environment that moves in the operator’s mental model.

Principle of Discriminability. Similar displays are often confused, so it is important that displayed information in one context should not display information in another.

Principle of Predictive Aiding. Operators should not have to do cognitively demanding mental simulations and should have predictions of future states of the craft.

Reference: Wickens & Hollands, 2002

Neilson’s (1994) Design Heuristics:

  • Visibility of system status. The system should keep users informed about what is going on, through appropriate feedback within reasonable time.
  • A match between system and the real world. The system should use words, phrases and concepts familiar to the user and information should appear in a logical order.
  • User control and freedom. Users can choose system functions by mistake, so it is important to provide an easily found “undo” function.
  • Consistency and standards. Consistency and standards should be followed so that operators do not have to question what words, situation or actions mean in different contexts.
  • Error prevention. Either eliminate error-prone conditions or check for conditions under which errors may occur to present users with the opportunity to confirm an option before making a decision.
  • Recognition rather than recall. Reduce an operator’s memory load by making objects, actions, and options visible so he or she does not have to recall from one dialogue to the next.
  • Implement flexibility and efficiency of use.
  • Implement aesthetic and minimalist design.
  • Help users recognize, diagnose, and recover from errors.
  • Provide help and documentation.

See also: Schneiderman, B. (1998) Designing the user interface.

Image via Digital Versus

Issues with paper vs. virtual displays

  • Orientation.  Paper is vertical, but displays are often horizontal.
  • Distance.  We read pages at a different distance than displays.
  • Refresh rate.  Video card can change refresh rate to be high so we do not perceive flicker on screens, but often there are still issues with flicker.  The smallest rate of flicker can create a distraction, reduce visibility and reduce performance.  There is obviously no issue with refresh rate with paper.
  • Contrast.  We cannot get the same kind of contrast on a display screen as we do with paper.
  • Luminance and reflectance. The amount of light falling on the paper or reflecting off paper does not interfere with legibility.  On a virtual display, there is the potential for reflection and luminance issues.

Data display

  • Left justify columns of alphabetic data for rapid scanning.
  • Label each page.
  • Maintain consistent format in displays.
  • Display data in directly usable forms.  Mental rotation should not be required to understand display.
  • Use short, simple sentences.
  • Provide a title for every display.
  • When blink coding is used, it should be 2 to 5 Hz.

Reference: Smith & Mosier, 1986

Screen design

  • Use abbreviations appropriately.
  • Avoid unnecessary details.
  • Use concise wording.
  • Use familiar data formats.
  • Use tabular formats with column headings.
  • Arrange related items as groups.
  • Use Highlighting to attract user attention.
  • Present information in proper sequences.

Reference: Tullis, 1988

~~~~~

Image via I Love Typography

Typography

There are several aspects of typography that are important to consider when designing an interface.

  • Stroke width: Boldness
  • Aspect ratio: Length and width of text
  • Font: Shape of letters
  • Font size: Size of letters
  • Kerning: Space between letters
  • Illumination: Brightness
  • Serif vs. Sans-serif
    • Serif fonts have non-structural details and elements on the ends of the strokes on some letters and symbols. I like to think of serif as feet.  Serif fonts are hard to read and should be avoided as a standard in most interfaces.  Times New Roman and Georgia are examples of Serif fonts.
    • Sans-serif fonts literally lack serif. Sans-serif fonts recommended or online use are Helvetica, Arial, Lucida Sans, Trebuchet MS and Verdana.  Calibri, Candara and Corbel are more popular now, but should be not be default fonts as they are in Microsoft Vista.
    • Italics in any font style should generally be avoided.

Check out Thinking with Type and Viget.com for some excellent information about legibility and typography.

~~~~~

Image via Matt Lewis

Color usage

Murch (1987) makes these recommendations:

  1. Avoid pure blue for text.
  2. Avoid thin lines and small shapes.
  3. Avoid red and green in the periphery of large-scale displays.
  4. Note that all colors are equally discernible.
  5. Do not overuse color.
  6. Use similar color to convey similar meaning.
  7. Use common background color for group-related elements.
  8. Use brightness and saturation to attract attention.
  9. Taking into account color-deficient viewers, avoid single color distinction.

Color combinations for user interfaces with graphic displays (Brown & Cunningham, 1989):

Background Best colors Worst colors
White Black, Blue Cyan, Yellow
Black Yellow, White Blue
Red Black Blue, Magenta
Green Black, Red Cyan
Blue Red, White, Yellow Black
Cyan Blue, Red Green, White, Yellow
Magenta Black, Blue Cyan, Green
Yellow Black, Blue Cyan, White

Reference: Wright, Mosser-Wooley & Wooley, 1997

~~~~~

Image via Sandel

Dynamic Display Principles

Information Need.  Operators should only be presented with information they need to complete the mission or objectives.  To avoid information overload, display design should be proceeded by a careful task analysis.

Proximity-Compatibility.  When commonly used information or instruments are far apart, it increases scanning and processing time.  For information that is relatable or must be integrated, these displays should be close together or integrated in some fashion to reduce the cognitive burden

Moving Part. The portion of the display that moves should correspond to that element of the environment that moves in the operator’s mental model.

Principle of Predictive Aiding. Rather than having to do cognitively demanding mental simulations, some displays can provide predictive aiding as to the future states of the aircraft so that pilots can “fly the plane.”  This type of display can reduce resources and facilitate anticipation of future states which is beneficial given the often sluggish nature of large aircraft

Principle of Discriminability. Because similar displays are often confused, it is imperative that displayed information in one context should never look like displayed information in another (i.e., that they are discriminable).

References: Roscoe, 1968; Sanders & McCormick, 1993; Wickens, et al., 1998; Wickens, 2003

~~~~~

Cluttered WOW raid via Sylvie Noel

Overlay, Integration and Clutter

Too much overlay can create clutter.  Clutter is defined as too much graphical information contained within too little a visual angle.  Extra clutter creates extra information processing demands.  User is forced to discriminate and ignore information they do not need so they can focus on mission critical information.  It is advantageous to integrate some information into single displays because the user needs to integrate the information mentally anyway.  Such integration is related to the Proximity-Compatability Principle.  Reducing visual scanning is even more valuable than reducing clutter or overlap. Visual scanning is effortful and time-consuming.  The interface should force the focus of attention on certain items (Wickens, 2000).

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