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)

• 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 Helmet-

Mounted 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 Helmet-

Mounted 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 data2) Comprehension, or synthesis of these disjointed data3) 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 signal-plus-noise trial. Vertical lines correspond to the criterion response

• d-prime and Beta in the steel industry

• Our current work

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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!