ITSD 4303 HumanComputer Interaction

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ITSD 4303Human-Computer Interaction

• Errors In Design
• DET (105-186)

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A Funny Fhoto
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Getting Gas

• True story (am I alone?)
• Pull into the gas station
• Start to pump
• Realize Im on the wrong side!

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Agenda

• Slips vs. Mistakes
• Forms of Slips
• Mistakes are For Everyone
• The Structure of Tasks
• Forcing Functions
• Evolutionary Design

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Slips vs. Mistakes

• What connotations arise when you hear
• I slipped up
• That was a mistake

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Slips

• Often minor errors
• You have the correct goal in mind
• But miss a detail (in the implementation)

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Forms of Slips

• Capture errors
• Description errors
• Data-driven errors
• Associative activation errors
• Loss-of-activation errors
• Mode errors

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Capture Errors
FrequentTask
Common Actions
Novel Task
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Description Errors

• Perform the specified action
• On the wrong object
• Often happen with distractions
• Locality/similarity an issue
• Experts are more prone

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Data-Driven Errors

• The world intervenes
• A sense is stimulated, triggering an automatic
  mental replacement
• Results in a Sorry, I was looking at I meant to
  say

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Associative Activation Errors

• We all have mental associations
• These can result in errors resulting in crossed
  wires in our brains
• These are typically the most embarrassing

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Loss-of-Activation Errors

• This is the forgetful type error
• Often, we cope by retracing our steps, or just
  continuing the action hoping for cues
• Perhaps explained with the brain reboot theory

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Mode Errors

• Very common among gadgets!
• Same interface acts differently depending upon
  context or state

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Designing for Slips

• Context and proximity an issue
• Example file deletion dialog
• Make recovery easy
• Example recycle bin / trash can

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Mistakes are For All

• Everyone makes mistakes
• Mistakes result from incorrect goals
• Why does this happen? Why dont we get the goals
  right?

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The Nature of the Mind

• We rely upon our memories
• Remember that we said long-term memories were
  processed
• Thus, we cant be objective when using our
  memories

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What Stands Out?
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The Odd and Normal

• Seem approximately the same in our long-term
  memories
• We tend to generalize the common
• There were a bunch of orange dots
• We tend to overemphasize the unique
• There was a white dot
• One orange dot stood out from the others

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How It Fits with Mistakes

• Our goals are formulated often based upon
• Patterns
• Emphasis on the unique
• Generalize the common
• Goals can then be misguided

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The Structure of Tasks

• How do we cope?
• Are all decisions hard?
• Decisions/tasks are easily broken into categories
• Shallow decisions
• Narrow decisions
• Deep/wide decisions

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Shallow Decisions

• Few tasks
• Often many choices at each level
• Emphasis is on competing options
• Ordering food
• Football

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Narrow Decisions

• Often many tasks
• Only a few alternatives at each point
• Emphasis is on execution of tasks
• Cooking
• Driving
• Passing a college course

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Deep/Wide Decisions

• Many tasks/steps
• Many alternatives at each point
• Games like chess, draughts/checkers
• How do we manage?

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Pruning

• Consider the decision tree
• Once youve reached a bad position, ditch that
  alternative and look elsewhere

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What To Do

• If we assume that slips and mistakes will happen
• How can we design such that we can help prevent
  these slips/mistakes?

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Forcing Functions

• Lets help protect the poor user from himself
• We must prevent this kind of action
• Purposeful constraints on behavior to force a
  sequence of actions

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The Seatbelt Dilemma

• The goal was to force people to wear seatbelts
• What were the problems that resulted?

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Forcing Function in Software

• What forcing functions do you see in software and
  everyday life?
• ATMsSaving work before closing a program

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Forcing Functions often Fail

• In the case of the seatbelt
• You could have a package in the passengers seat
• The technology failed, so the buzzing persisted
  or the car wouldnt start
• In the case of the gas tank latch
• Wanted to prevent the door from opening

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Philosophy of Errors in Design

• Assume errors will be made
• Dont equate errors as incorrect
• Make actions easily undone
• Mitigate possible problems as a result of errors
• Think about the design from a users perspective

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FIN