CEN 3722 Human Computer Interaction Title of Presentation

CEN 3722 Human Computer Interaction Title of Presentation Dr. Ron Eaglin

Outcomes • Explain why designers should not blame users for errors. • Describe types of errors, slips, and mistakes. • Describe the various types of slips. • Describe how to design to minimize errors

Outcomes • Define and provide examples of these types of slips • Capture errors, mode errors, description errors, data-driven errors, associative-activation errors, loss of activation errors • Describe these forcing functions • Gag, warn, do nothing, do what I mean, Let’s talk about it, teach me.

Consequences of Human Error • 1998 USSR Phobos satellite lost on trip to Mars • Ground controller omitted a single letter in a series of digital commands sent to the space craft. • The omission caused code to be mistranslated to trigger a test sequence stored in ROM. • This also launched hundreds of conspiracy theorists – simply Google “Phobos UFO”

Blame • Effects of electrical noise on signal reliability (well known phenomenon). • Designers often use error correction codes. • If Phobos malfunction had caused Phobos loss – would ground control have been blamed? • Error correction codes were standard practice. • Where is blame assigned?

Facts • People make mistakes • Creativity, adaptability, and flexibility are human strengths • Alertness and precision in action or memory are our weaknesses • We have identified class of errors and conditions likely to evoke them • We can design for error.

Humans vs. Computers • Humans deal with human errors and correct all the time • Yu cn stll rd ths Sntnc bt a mchn cnt. • Machines need precision – do not tolerate errors well

Dealing with Errors • In Design – devise systems to minimize errors • Make it easier to deal with errors • Provide clear indication of causes and remedies • Provide tools to make correction easier

Example

Example • Outlook 360 will prompt you to ask you if • You mention an attachment in the body of your mail • You don’t attach an attachment to the mail.

Types of Errors • Mistakes and Slips • A person establishes an intent to act – if the intention is not appropriate this is a mistake. • Misdiagnosis or misinterpretation of the situation. • Example: Incorrectly hitting send on incomplete email. • If the intent is appropriate, but action is not what was intended this is a slip. • Example: a typo caused by improper hand placement on keys.

Slip – Capture Error • Done when a frequently done activity – takes over the intended action. • Example: Turning wrong direction in car based on habit – when you intended to go other direction • Example: Typing a common word incorrectly based on other words typed with a common letter sequence • Example: Typing the wrong phone number if you have one you commonly dial.

Slip – Capture Error (correction) • Avoid using common sequences for infrequent commands (Such as Ctrl-C, Ctl –V – Copy Paste) • Provide feedback mechanism to tell users what they are performing (You are attempting send the message without the attachment) • Have system understand the context of the commands and act/warn user accordingly.

Slips – Description Error • Happens when there is insufficient specification of the action • Ambiguity leads to incorrect action being performed • Caused by lack of consistency in command structures

Slips - Description Error • Ensure options a clearly differentiated (like a row of switches) • Provide sufficient feedback about action and consequence • Slips that can go unnoticed need to have feedback mechanism

Slips – Data Driven Error • Unconscious processing of external data interferes with intention • Typing what you are thinking not what you intended • Calling your wife/child/friend by wrong name • Saving file with wrong name

Slips – Data-Driven Error • Minimize distractions when consequences are severe • Provide clues as to intent of user (if predictable) • Give suggestions for things like file name, catch obvious slips

Slips – Loss of activation error • You forget what you are doing in mid-flow • Example: talking on phone/forgetting why you called

Slips – Loss of activation errors • Use cognitive reminders • Understand common patterns with suggestions • Lists or process flows to stay on track

Slips – Mode Error • When you think you are in one state, but actually in another • Example: CAPS LOCK BEING ON AND TYPING IN ALL CAPS

Slips – Mode Error • Avoid use of modes • Make system states are obvious, many cues • Make it easy to correct or catch • “You just typed an email message in all CAPS, did you intend to do this or should I correct it? ”

Design for Errors • Anticipate human errors and prevent then • Forcing Function – prevents the behavior from continuing until the problem has been corrected. • Guarantees detection but not correction • Example: disable buttons • Example: Don’t allow car to lock if keys inside (require keys to lock car)

Forcing Functions - Gag • Prevents user from continuing if error state • Computer locks unless computer and monitor are on • Car wheels locked unless key in ignition

Forcing Functions - Warn • Warning – File already exists, overwrite? • Seat belt light and audio alarm

Forcing Function – Do Nothing • If action is illegal or in error – nothing happens • No user feedback, can cause frustration

Forcing Function – Self Correct • System guesses legal action you want to perform • Example: Spell check – provides much humor on cell phones • Do What I Mean – Ultimate self correct function

Summary • Explain why designers should not blame users for errors • Describe common slips and mistakes and differences • Describe different types of slips and forcing functions