Errors Lecture
Errors and Cognitive Processes
Have to Put It All Together to Understand Errors
and Higher Level Cognition
Many Sources of Error
Attention
Pattern Recognition
Memory
Problem Solving (Controlled Processing)
Skilled Performance (Automatic Processing)
Correct Performance Can Give Us Surprisingly Little
Information About Underlying Mechanisms
Assumption About Underlying Mechanisms Can Make
Strong Predictions Concerning Errors.
Page 1
Errors Lecture
Definitions of Errors (From Kieras
Lectures on Error)
Basic concept
An intention or plan is formed
Actions to accomplish the intention are executed
Errors are Intentional but Incorrect Actions
Errors of Commission
Errors of Omission
Slip
Actions were not executed correctly
Plan to push the stop button, hit the start button instead.
Mistakes
The wrong intention or plan was constructed
Could be correctly executed
Page 2
Errors Lecture
Errors and Operation of Complex Systems
(Kieras)
Errors made immediately by operators of a system
Latent errors
Errors made by designers, decision makers, construction
& maintenance workers, etc.
Don't necessarily have an effect until some special
circumstances
"accident waiting to happen"
Page 3
Errors Lecture
Errors and Complex Systems (Cont.)
Violations
Deliberate deviations from socially defined practice
Routine violations
• Make task easier
• No enforcement in place
• E.g. cutting across grass
Exceptional violations
• Result from combinations of social & organizational
forces
• Can result in suppression of warnings, major
management errors
E.g. Chernobyl accident
• Reactor deliberately operated against the rules, at a
power level known to be unsafe, supervised by unqualified
Page 4
Errors Lecture
Errors As Data On Cognitive Processes
Assumption About Underlying Mechanisms Can Make
Strong Predictions Concerning Errors.
Recall Errors From STM
Errors in Multicolumn Subtraction
Typing Errors
Accident Investigations
Methods for Studying Human Error (From Kieras)
Error behavior is hard to study
Error events are hard to capture
In laboratory studies
Many different ways to make an error
Erroneous behavior normally not analyzed
Errors often have low frequency
Page 5
Errors Lecture
Studying Errors (Cont)
Major sources of information on errors
Detailed analysis of accidents
• Note that errors could have happened a long time
before
Diary studies
• People write down errors soon after they happen
Classifying Errors
Classification is difficult; needs a better theoretical model
than currently available
Page 6
Errors Lecture
More On Slips and Mistakes
Two Major Kinds of Errors
Slips
Mistakes
Slips
Correct Goal or Intention
Have Necessary Knowledge and Skills
Familiar Situations
Wrong Action Sequence
Show Up In Skilled, Highly Automated Behavior
Mistakes
Incorrect Goal or Intention
Lack of Necessary Skills or Knowledge
Novel Situations
Problem Solving Behavior
Controlled Processing
Page 7
Errors Lecture
Procedural Knowledge, Goals, and
Activation
Execution of Procedural Knowledge is Controlled by ACTIVE
Goals
A Set of Rules that Performs a Task Has a Common
Controlling, ACTIVE GOAL
A Schema that Performs a Task Has a Common Controlling,
ACTIVE GOAL
Schacter and Errors
The Sin of Absentmindedness
Error of Omission
Failure to Successfully Activate Goal Associated with ToBe Performed Action
Page 8
Errors Lecture
Activation-Trigger-Schema (ATS)
Norman (1981, 1988)
Activation
• Priming (Preparation) verses Execution
• Triggered Schema With Most Active Goal Controls
Behavior
• Loss of Activation of Goal Causes Schema to Lose
Control
Trigger(s)
• Like Conditions of Rules
• Trigger Execution of Primed Schema
• Context Cues Provide Triggering Information
Schemas
• Complex Skills Like Driving Home
• Hierarchies of Goals and Subgoals
• Actions That Accomplish Goals and Subgoals
• Role of Triggers and Activation In Schema Execution
Schema  Collect of Rules to Performs a Task
Sequence of Actions that Performs A Task
Page 9
Errors Lecture
Slips in the ATS Model
Errors In Formation Of Goals Or Understanding Context
Faulty Activation Of Schemas
Faulty Triggering Of Active Schemas
Page 10
Errors Lecture
Slips That Result From Errors In
Formation Of Goals Or Understanding
Context
Description Errors
Ambiguous or incomplete description of the goal and/or
situation
Perform Correct Action on Wrong Object
Examples
"Come in" to phone...
Use phone hand set to continue dictating
Throwing Dirty Shirt in ...
Pour Orange Juice in ...
Mode Errors
Erroneous classification of the situation
Examples
Text editors
Multifunction controls
Serious problem in high automated systems
Page 11
Errors Lecture
Examples From Class
Using a Mac In Norlin…
After siting down and logging on, I dug out my materials and
my zip disk and set to work.
However, when I attempted to load my work disk I found that
it would not fit into the drive.
I thought to myself that perhaps the lab was one of the ones
that did not have zip drives.
I was about to start putting my things away before I realized
that the computer had both a zip and a 3.5" drive, and I
had simply tried to use the wrong one.
Though I felt somewhat stupid for the mistake, I was relieved
I did not have to pack back up and move, and I completed
my paper.
I repeatedly tried to open my front door using my work key
until I finally realized that I was home now and needed to
use something different.
Page 12
Errors Lecture
Slips That Result From Faulty Activation
of a Schema
Unintentional Activation:
When schemata not part of correct action sequence
become activated for extraneous reason, then triggers
generating slips.
• Capture errors
• Data-driven activation
• Associative activation
Loss of Activation:
When schemata that have been activated lose activation,
thereby losing effectiveness to control behavior
• Forgetting an intention (Sin of Absentmindedness)
• Mis-ordering the components of an action sequence
• Skipping steps in an action sequence
• Repeating steps in an action sequence
Page 13
Errors Lecture
Unintentional Activation: Errors Caused
by Incorrect High Activation of Wrong
Action or Schema
• Capture errors
• Data-driven activation
• Associative activation
Capture Errors
Two Different Action Sequences
Identical or Similar Initial Steps In Common
One Sequence is Very Familiar, The Other Not
Examples
Go to the store...
Getting dressed for dinner...
Page 14
Errors Lecture
Unintentional Activation (Cont.)
Data Driven Errors
Automatic Actions Are Data Driven
Examples
Dial the room number ...
Example From Class
I was trying to write down the subject number of one of the
participants in an experiment, but was talking to a friend
about drinking age at the time, and instead of writing 19
(the subject number), I wrote 21 (the drinking age)
Associative Activation Errors
Priming of Related Schema
Related to Capture Errors and Data Driven Errors
Examples
Say “Come In” to the phone..
Page 15
Errors Lecture
Errors Caused By Loss Of Activation
Forgetting a Goal or Subgoal
Interruptions
Subgoal Kill Off
Examples
Skipping a Step In a Highly Learned Procedure
Forget to Take Pills
Enter Account Number Followed by ...
Go to the bedroom to ...
Page 16
Errors Lecture
Examples From Class
One morning, as I was settling down to eat breakfast in my
kitchen, I suddenly remembered something and ran into
my room to take care of it.
When I got into my room, I stopped and stared at my desk.
I knew I had come into the room for something, and I felt like
it was something from my desk though I was not sure
what.
I slowly looked over my desk and came upon my checkbook.
That did it.
I needed to write my roommate a check for my share of the
paper, which I had just sat down to read in the kitchen.
I woke up and was going to work.
I got in the car the windows were frosty.
I turned on the defroster, reached behind me to unlock the
back door and got out closing my door.
However, I didn't unlock the back door and I automatically
locked my door locking myself out of the car.
Needless to say I was locked out of my running car and don't
even remember locking my door before getting out to
scrape the windows.
Page 17
Errors Lecture
Slips That Result From Faulty Triggering
of Active Schemata
False Triggering:
A properly activated schema is triggered at an in
appropriate time
Failure to Trigger
When an active schema never gets invoked because
• Action was preempted by competing schemata
• There was insufficient activation
forgetting
initial level to low
• There was a failure of the trigger condition to match
conditions badly specified
poor match between required conditions and
current context
Sin of Absentmindedness
Page 18
Errors Lecture
Detection of Errors
Modes of Error Detection
Self monitoring
Feedback from the environment
Intervention by another person
Interactions with the Cognitive Modes
Slips
Mistakes
Page 19
Errors Lecture
Self Monitoring
Action Slips
Nature of skill-based performance
Specification of correct action sequence
Processes that utilize this knowledge
Attention allocation
Role of feedback from the environment
Errors During Problem Solving
Knowledge-based action
Depends on
Correct goal
Ability to detect deviation from solution path
Impact of wrong goal (strategic mistake)
Page 20