SUMMARY COURSE 3.6:
OCCUPATIONAL HEALTH AND
SAFETY
BY ROWAN MOELIJKER
YEAR 2018/2019
POSITIVE & ORGANIZATIONAL PSYCHOLOGY
ERASMUS SCHOOL OF SOCIAL AND BEHAVIOURAL SCIENCES
,PROBLEM 2: ACCIDENTS, ERRORS & SAFETY
THEORIES OF HUMAN ERROR AND ACCIDENTS
NORMAN, D. (2013). HUMAN ERROR? NO, BAD DESIGN. IN D. NORMAN, THE DESIGN OF
EVERYDAY THINGS. (PP. 162-216) BASIC BOOKS ISBN: 978-0-465-05065-9
Professor notes: This relatively large chapter contains a lot of information about human error and design.
Although the chapter is almost 50 pages, it is written quite well and rather easy (and fun) to read.
Understanding Why There is Error
Errors can occur for many reasons. The most common is in the nature of the tasks and procedures that require
people to behave in unnatural ways (e.g. staying alert for hours at a time). Interruptions are a common reason
for error, not helped by designs and procedures that assume full, dedicated attention yet that do not make it
easy to resume operations after an interruption.
When an error leads to losses (e.g. costs or injury), a special committee is convened to investigate the cause
and, almost without fail, guilty people are found. The next step is to blame and punish them. This doesn’t cure
the problem: the same error will occur over and over again. When an error occurs, the product or procedures
should be redesigned.
Root Cause Analysis
This means that an accident is investigated until the single, underlying cause is found. Trying to find the cause
of an accident sounds good but it is flawed for two reasons:
1. Most accidents do not have a single cause.
2. Root cause analysis often stops once a human error is found. We should discover what led to a human error,
to apply why the error occurred and what can be done to prevent it.
The Five Whys
This means that when searching for a reason, even after you’ve found one, do not stop: ask why that was the
case. And then ask why again. This does not take exactly five times, but calling the procedure “Five Whys”
emphasizes the need to keep going even after a reason has been found.
The Five Whys do not guarantee success. The question why is ambiguous and can lead to different answers by
different investigators.
One big problem is that the natural tendency to blame someone for an error is even shared by those who made
the error, who often agree that it was their fault. People do tend to blame themselves when they do something
that, after the fact, seems inexcusable. When we blame people, it is then difficult to convince organisations to
restructure the design to eliminate these problems.
A major cause of error is time stress. There is a lot of pressure to push ahead with work even when an outside
observer would say it was dangerous to do so.
Deliberate Violations
Deliberate violations are defined as cases where people intentionally violate procedures and regulations.
Routine violations occur when noncompliance is so frequent that it is ignored. Situational violations occur when
there are special circumstances (e.g. going through a red light because you were late and no other cars were
visible. In some cases, the only way to complete a job might be to violate a rule or procedure.
A major cause of violations is inappropriate rules or procedures that not only invite violation but encourage it.
Although violations are a form of error, these are organisational and societal errors, important but outside the
scope of the design of everyday things. The human error examined here is unintentional.
, Two Types of Errors: Slips and Mistakes
Reason and Norman developed a general classification of human error. It is divided into two major categories:
slips and mistakes.
Human error is defined as any deviance from “appropriate behaviour”. In many circumstances, the appropriate
behaviour is not known or is only determined after the fact.
Error is the general term for all wrong actions.
Slips occur when a person intends to do one action and ends up doing something else. There are two major
classes of slips: action-based and memory lapse. In action-based slips, the wrong action is performed (e.g.
putting an empty milk carton into a fridge instead of a trash can). In lapses, memory fails, so the intended
action is not done or its results are not evaluated (e.g. forgetting to turn off stove).
Mistakes occur when the wrong goal is established or the wrong plan is formed. From that point on, even if the
actions are executed properly they are part of the error, because the actions themselves are part of the wrong
plan and therefore inappropriate.
Mistakes have three major classes:
Rule-based: the person has appropriately diagnosed the situation, but then decided upon an erroneous course
of action: the wrong rule is being followed.
Knowledge based: the problem is misdiagnosed because of erroneous or incomplete knowledge.
Memory lapse: take place when there is forgetting at the stages of goals, plans, or evaluation.
The Classification of Slips
Most everyday errors are slips. An interesting property of slips is that they tend to occur more frequently to
skilled people than to novices. This is because slips often result from a lack of attention to the task. Skilled
people tend to perform tasks automatically, while novices have to pay considerable conscious attention.
There are numerous different kinds of action slips, categorized by the underlying mechanisms that give rise to
them.
1. Capture slips: a situation where, instead of the desired activity, a more frequently or recently performed one
gets done instead: it captures the activity. Capture errors require that part of the action sequences involved in
the two activities be identical, with one sequence being far more familiar than the other. Capture errors are
therefore partial memory-lapse errors. Designers need to avoid procedures that have identical opening steps
but then diverge.
2. Description-similarity slips: here the error is to act upon an item similar to the target. This happens when
the description of the target is sufficiently vague. A description that usually suffices may fail when the situation
changes so that multiple similar items now match the description. These errors result in performing the correct
action on the wrong object. Designers need to ensure that controls and displays for different purposes are
significantly different from one another.
3. Mode-error slips: this error occurs when a device has different states in which the same controls have
different meanings: we call these states modes. In industry, the confusion that results when operators believe
the system to be in one mode, when reality it is in another, has resulted in serious accidents and loss of life.
Mode error is really design error. Mode errors are especially likely where the equipment does not make the
mode visible, so the user is expected to remember what mode has been established, sometimes hours earlier,
during which time many intervening events might have occurred. Designers must try to avoid modes, but if
necessary, the equipment must make it obvious which mode is invoked.
Memory-lapse slips: errors caused by memory failure. The immediate cause of most memory-lapse slips is
interruptions, events that intervene between the time an action is decided upon and the time it is completed.
There are several ways to combat memory-lapse errors. One is to minimize the number of steps; another, to
provide vivid reminders of steps that need to be completed.
OCCUPATIONAL HEALTH AND
SAFETY
BY ROWAN MOELIJKER
YEAR 2018/2019
POSITIVE & ORGANIZATIONAL PSYCHOLOGY
ERASMUS SCHOOL OF SOCIAL AND BEHAVIOURAL SCIENCES
,PROBLEM 2: ACCIDENTS, ERRORS & SAFETY
THEORIES OF HUMAN ERROR AND ACCIDENTS
NORMAN, D. (2013). HUMAN ERROR? NO, BAD DESIGN. IN D. NORMAN, THE DESIGN OF
EVERYDAY THINGS. (PP. 162-216) BASIC BOOKS ISBN: 978-0-465-05065-9
Professor notes: This relatively large chapter contains a lot of information about human error and design.
Although the chapter is almost 50 pages, it is written quite well and rather easy (and fun) to read.
Understanding Why There is Error
Errors can occur for many reasons. The most common is in the nature of the tasks and procedures that require
people to behave in unnatural ways (e.g. staying alert for hours at a time). Interruptions are a common reason
for error, not helped by designs and procedures that assume full, dedicated attention yet that do not make it
easy to resume operations after an interruption.
When an error leads to losses (e.g. costs or injury), a special committee is convened to investigate the cause
and, almost without fail, guilty people are found. The next step is to blame and punish them. This doesn’t cure
the problem: the same error will occur over and over again. When an error occurs, the product or procedures
should be redesigned.
Root Cause Analysis
This means that an accident is investigated until the single, underlying cause is found. Trying to find the cause
of an accident sounds good but it is flawed for two reasons:
1. Most accidents do not have a single cause.
2. Root cause analysis often stops once a human error is found. We should discover what led to a human error,
to apply why the error occurred and what can be done to prevent it.
The Five Whys
This means that when searching for a reason, even after you’ve found one, do not stop: ask why that was the
case. And then ask why again. This does not take exactly five times, but calling the procedure “Five Whys”
emphasizes the need to keep going even after a reason has been found.
The Five Whys do not guarantee success. The question why is ambiguous and can lead to different answers by
different investigators.
One big problem is that the natural tendency to blame someone for an error is even shared by those who made
the error, who often agree that it was their fault. People do tend to blame themselves when they do something
that, after the fact, seems inexcusable. When we blame people, it is then difficult to convince organisations to
restructure the design to eliminate these problems.
A major cause of error is time stress. There is a lot of pressure to push ahead with work even when an outside
observer would say it was dangerous to do so.
Deliberate Violations
Deliberate violations are defined as cases where people intentionally violate procedures and regulations.
Routine violations occur when noncompliance is so frequent that it is ignored. Situational violations occur when
there are special circumstances (e.g. going through a red light because you were late and no other cars were
visible. In some cases, the only way to complete a job might be to violate a rule or procedure.
A major cause of violations is inappropriate rules or procedures that not only invite violation but encourage it.
Although violations are a form of error, these are organisational and societal errors, important but outside the
scope of the design of everyday things. The human error examined here is unintentional.
, Two Types of Errors: Slips and Mistakes
Reason and Norman developed a general classification of human error. It is divided into two major categories:
slips and mistakes.
Human error is defined as any deviance from “appropriate behaviour”. In many circumstances, the appropriate
behaviour is not known or is only determined after the fact.
Error is the general term for all wrong actions.
Slips occur when a person intends to do one action and ends up doing something else. There are two major
classes of slips: action-based and memory lapse. In action-based slips, the wrong action is performed (e.g.
putting an empty milk carton into a fridge instead of a trash can). In lapses, memory fails, so the intended
action is not done or its results are not evaluated (e.g. forgetting to turn off stove).
Mistakes occur when the wrong goal is established or the wrong plan is formed. From that point on, even if the
actions are executed properly they are part of the error, because the actions themselves are part of the wrong
plan and therefore inappropriate.
Mistakes have three major classes:
Rule-based: the person has appropriately diagnosed the situation, but then decided upon an erroneous course
of action: the wrong rule is being followed.
Knowledge based: the problem is misdiagnosed because of erroneous or incomplete knowledge.
Memory lapse: take place when there is forgetting at the stages of goals, plans, or evaluation.
The Classification of Slips
Most everyday errors are slips. An interesting property of slips is that they tend to occur more frequently to
skilled people than to novices. This is because slips often result from a lack of attention to the task. Skilled
people tend to perform tasks automatically, while novices have to pay considerable conscious attention.
There are numerous different kinds of action slips, categorized by the underlying mechanisms that give rise to
them.
1. Capture slips: a situation where, instead of the desired activity, a more frequently or recently performed one
gets done instead: it captures the activity. Capture errors require that part of the action sequences involved in
the two activities be identical, with one sequence being far more familiar than the other. Capture errors are
therefore partial memory-lapse errors. Designers need to avoid procedures that have identical opening steps
but then diverge.
2. Description-similarity slips: here the error is to act upon an item similar to the target. This happens when
the description of the target is sufficiently vague. A description that usually suffices may fail when the situation
changes so that multiple similar items now match the description. These errors result in performing the correct
action on the wrong object. Designers need to ensure that controls and displays for different purposes are
significantly different from one another.
3. Mode-error slips: this error occurs when a device has different states in which the same controls have
different meanings: we call these states modes. In industry, the confusion that results when operators believe
the system to be in one mode, when reality it is in another, has resulted in serious accidents and loss of life.
Mode error is really design error. Mode errors are especially likely where the equipment does not make the
mode visible, so the user is expected to remember what mode has been established, sometimes hours earlier,
during which time many intervening events might have occurred. Designers must try to avoid modes, but if
necessary, the equipment must make it obvious which mode is invoked.
Memory-lapse slips: errors caused by memory failure. The immediate cause of most memory-lapse slips is
interruptions, events that intervene between the time an action is decided upon and the time it is completed.
There are several ways to combat memory-lapse errors. One is to minimize the number of steps; another, to
provide vivid reminders of steps that need to be completed.
