Some general psychological
considerations in relation to safety
Angus Gellatly
What we are and what we do
There are often said to be three domains of ergonomics:
physical, cognitive, and organizational. However, other
terms are also used (social, workplace, child ergonomics),
and even the three domains are not clearly distinguishable.
One of my themes is that it can be dangerous to focus on a
single domain to the exclusion of the others.
Start with 2 examples of physical ergonomics, the second
of which merges into cognitive and social psychology
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Evacuating very large transport aircraft
(VLTA)
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Cross-aisles increase
Panic levels
Sill heights
Wheel-chair egress
Cookers, aesthetics and
economics
OR
Why don’t manufacturers do more product
testing on appropriate user populations?
Is ‘Microsoft Help’ an abuse of language?
A great deal of classical aviation ergonomics
focussed on display design issues such as
those exemplified by the cooker design
example. These included:
1.What information to display?
2.How to display for good comprehension?
3.Relationship of displays to controls.
Advantages of Head-Up and HelmetMounted displays.
From the mid-1980’s, the emphasis shifted
to social dynamics and personality types.
HUD in a Pontiac Bonneville
showing a speed of 47 mph
A great deal of classical aviation ergonomics
focussed on display design issues such as
those exemplified by the cooker design
example. These included:
1.What information to display?
2.How to display for good comprehension?
3.Relationship of displays to controls.
Advantages of Head-Up and HelmetMounted displays.
From the mid-1980’s, the emphasis shifted
to social dynamics and personality types.
Crew Resource Management (CRM)
EXAMPLE: At take off in winter 1982, ice in a sensor
caused the speed indicators to read too high, leading the
captain to apply too little power as the plane ascended:
First Officer: Ah, that's not right.
Captain: Yes, it is, there's 80 [referring to speed].
First Officer: Nah, I don't think it's right. Ah, maybe it is.
Captain: Hundred and twenty.
First Officer: I don't know.
It wasn't right, and the First Officer's muting his concerns
led to the plane's stalling and crashing into a Potomac River
bridge, killing all but five people on board.
Crew Resource Management (CRM)
Due to mounting evidence of this sort of failure, the
emphasis in aviation safety shifted from perfecting the
presentation of information to the issue of how
information is used within a social group and to
selection of personnel appropriate to the task at hand.
The notion of Situation Awareness became central to
CRM and has subsequently been adopted in many
domains from military command and control to
organisational and nuclear power station management
(though not, it seems, in banking!). Elements include:
1) Perception of relevant data
2) Comprehension, or synthesis of these disjointed data
3) Projection – Of the changing state of the system into
the future
• Situation Awareness is a melange of cognitive and
social factors, but these can be summarised as:
• 1) Who knows what? – Perception and cognition of
relevant data
• 2) Who listens to whom? – So who is influenced by
whom?
Signal detection theory
Internal response probability of occurrence curves for noise-alone and
signal-plus-noise trials. Since the curves overlap, the internal response
for a noise-alone trial may exceed the internal response for a signalplus-noise trial. Vertical lines correspond to the criterion response
• d-prime and Beta in the steel industry
• Our current work
Target duration = 17 ms
Mask type
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Sim. On/Off
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Sim. On; Delay. Off
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Target duration = 200 ms
T
Sim. On/Off
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Sim On; Delay. Off
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Delay On/Off
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Target duration = 500 ms
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Sim. On/Off
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Sim On; Delay. Off
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Delay On/Off
50
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Correct responses (%)
90
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• N2pc is believed to be an index of attentional target selection. It is
highly surprising that for such an easy task the very early functioning
of the visual system is influenced by the reward value of the target.
• This demonstrates once again the high degree of interconnection
across the various levels or facets of human functioning investigated
by psychologists and ergonomists.
• Physical, cognitive and social factors all influence performance, and
can even have interactive effects upon one another.
• This makes it impossible to derive hard and fast rules in relation to
human performance. Every situation or task is different, maybe
even different for different users or user populations. Psychologists
are more likely to know what questions to ask in relation to a new
problem than what answers to give. Answers require empirical
testing, and even then the most relevant factors may be missed!