CS 851: Forensic Software Engineering
Human Error by James Reason
Chapter1:
The nature of error
Chapter2:
Studies of human error
RAJAT TIKOO
18th October, 2002
The nature of error
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Reason opens with examples of accidents caused due to
human error:
Three Mile Island (1979)
Bhopal Gas Tragedy (1984)
Challenger mission (1986)
Chernobyl disaster (1986)
Others….
• “Knowledge and error flow from the same mental sources,
only successes can tell the one from the other.” (Mach, 1905)
Cognitive balance sheet
• The underlying theme:
“Correct performance and systematic errors are two sides of
the same coin.”
• A knowledge base that contains specialized theories preserves
meaning, yet can lead to confirmation bias.
• Errors involved in boiling an egg?
• But (in reality) human error is neither abundant nor as varied
as its vast potential might suggest.
• Are errors predictable?
Variable and Constant errors
Intentions, actions and consequences
Was there a prior intention to act?
If No, was there intention in the action ?
If no, then involuntary/non-intentional action
else spontaneous/subsidiary action
If Yes, did the actions proceed as planned?
If no, unintentional action (slip/lapse)
If yes, did the actions achieve their desired end?
If no, intentional but mistaken action
If yes, successful action
Error: working definitions
• Errors: planning failures (mistakes) and execution failures
(slips and lapses)
• “Error will be taken as a generic term to encompass all those
occasions in which a planned sequence of mental or physical
activities fails to achieve its intended outcome, and when these
failures cannot be attributed to the intervention of some chance
agency.”
• Slips and lapses are errors which result from some failure in
the execution and/or storage stage of an execution sequence,
regardless of whether the plan which guided them was
adequate to achieve its objective.
Error: working definitions
• Mistakes may be defined as deficiencies or failures in the
judgmental and/or inferential processes involved in the
selection of an objective or in the specification of the means to
achieve it, irrespective of whether or not the actions directed
by this decision scheme run according to plan.
• Thus, mistakes are likely to be more subtle, more complex and
less well understood than slips.
• Comments on this definitions?
Classification of errors
• Behavioral level of classification (What?)
Errors are classified according to some observable features of
the erroneous behavior (omission, repetition, reordering).
• Contextual level of classification (Where?)
Why did the error occur at a particular position in a particular
behavioral sequence?
• Conceptual level of classification (How?)
Based on the assumptions about the cognitive mechanisms
involved in error production.
Error Types
• A sequence of action has three stages: planning, storage and
execution.
Cognitive Stage
Planning
Storage
Execution
Primary error type
Mistakes
Lapses
Slips
Methods of investigating error
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Naturalistic methods or “corpus gathering”
Questionnaire studies
Laboratory studies
Simulator studies
Case studies
• Comments/ Questions?
Chapter 2: Studies of Human Error
Early psychological observers of human error:
• Sully’s Illusions (1881)
“Any species of error which counterfeits the form of
immediate, self-evident or intuitive knowledge, whether as
sense-perception or otherwise”
• The Freudian slip (1896)
“…he became convinced that all of these normally
inconsequential slips and lapses betrayed the presence within
the unconscious of repressed impulses.”
• Meringer and speech errors (1895)
Chapter 2: Studies of Human Error
• The Gestalt tradition (1912)
Holistic view to physiological phenomena
• Lashley and Head (The neurophysiologists) (1917-1920)
How is relatively automatic performance characteristic of
skilled or highly practiced behavior achieved?
• Bartlett (1932)
Used the notion of schema to explain systematic errors
Chapter 2: Studies of Human Error
• Bartlett (1932)
A schema is “an active organization of past reactions, or
of past experiences, which must always be supposed to be
operating in any well-adapted organic response. That is
whenever there is any order or regularity in behavior, a
particular response is possible only because it is related to
other similar responses which have been serially organized, yet
which operate, not simply as individual members coming one
after another, but as a unitary mass.”
The natural science tradition
• Focused attention and bottleneck theories
Is there a bottleneck in information processing by humans?
i.e. at what stage does a parallel processing system, capable of
handling several inputs at the same time, become transformed
into a serial system through which only one set of signals
could be handled at any given moment?
-Dichotic listening
• Contradictory views
The natural science tradition
• Divided attention and resource theories
Subjects asked to distribute their attention between the
assigned activities and to deal with them to the best of their
ability.
Interference can occur – the main interference can occur when
the two tasks compete for the same functions.
• Multichannel processor theories
advocates against the above which assume the existence of a
GPLCCP.
The natural science tradition
• Allan Allport (1980)
“In general, we suggest, any complex task will depend on the
operation of a number of independent, specialized processors,
many of which may be common to other tasks.”
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Properties of primary memory
STM (Short Term Memory)
e.g. remember a larger number like 196443404412,
Easier to remember in chunks
Immediate memory span ~ 7 items
The natural science tradition
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Concept of working memory (1974 - )
Derived from STM
A central executive (capacity control resource)
2 slave systems:
Articulatory loop
Visuospatial scratchpad
• There is a competition between resources needed to preserve
temp. data generated during processing and those consumed
by the processing itself.
The Cognitive Science tradition
• Contemporary schema theories
data structures for representing concepts stored in memory.
• The Norman-Shallice model
horizontal and vertical threads
• Subjective Utility Theory
• Reluctant rationality
Cognitive Strain and Persistence forecasting
The Cognitive Science tradition
• General Problem Solver (GPS)
Problem behavior graph
• Rouse’s “fuzzy rule” model
Derived from GPS
• Ramussen’s framework
skill-based, rule-based and knowledge based levels
• Parallel Distributed Processing (PDP)
• Global Workspace (GW) model
Conclusions
• Common themes/principles
• Controlled Processing vs Automatic Processing
• “The price we pay for this largely automatic processing of
information is that perceptions, memories, thoughts and
actions have a tendency to err in the direction of the familiar
and the expected.”