vrijdag 26 oktober 2007

Action Slips, Lapses and Mistakes

Notes taken from October 24th meeting

‘His mind wanders, but we don’t worry, it’s too weak to get far.’ Reader’s digest

Because to err is human, and we are more human than most I thought Error Slips would be a great topic for the group.

Objective: To understand why errors occur and ask if we can we avoid them happening?

Captain Kirk’s Fatal Error

Research into human errors has been prompted by concern over professional and workplace errors e.g. see this link about therac-25 for the classic story of a series of blunders in the administration of a radiation dose to cancer patients.

The first therac-25 patient to die of radiation sickness was Ray Cox whose sanguine last words were ‘Captain Kirk forgot to put his machine on stun.’


Mistakes involve either insufficient knowledge (e.g. announcing ‘Je suis plein ‘at a dinner party without awareness of it’s common meaning) or planning errors (e.g. not allowing sufficient time for a job, in spite of previous experience of the time required)

However, beware of planning an action whilst finishing another- can lead to a blend error where the actions fuse together e.g., I sent an e-mail to a pupil’s mother, signed love Mum

Because I was thinking about the next e-mail to my son as I signed the one I was writing

Lapses involve prospective memory failure -of things you intend to do- sending a birthday card for example.

Errors occur past the planning stage, during the execution of an action.

One common type of error- action slips occurs when we are ‘running on automatic.’

Working memory capacity, the things we can hold in mind at one time-is extremely limited, therefore we do a lot of our everyday actions using a rag bag of automatic routines. Automaticity is not in general a bad thing, once we have learnt a technique it frees our attention so we can-walk, drive, and make a cup of coffee with out overmuch thought


But the lack of conscious input makes this automatic mode prone to interference –

Some types of Action Slips

Plan: Get up, make coffee. Result: Pour orange juice in coffee.

A description error slip, probably because the orange juice has much in common with milk (appearance of carton, used at breakfast)

Plan: Take family to Pirates of Caribbean. Result: Take road to office.

A’ capture’ slip, your drive to the cinema was ‘captured’ by an automatic drive to office routine.

Plan: Forgotten: Result: Why am I in this room? What am I looking for? ‘Loss of activation’ slips when you lose track of what you’re trying to do.

Prevention of errors

Think ahead, to spot the type of tasks that are extremely prone to error; in fact the characteristics of error provoking tasks have been enumerated-

Why I always leave the last page of the original in the photocopier

The foremost scientist in the study of human error is Professor Reason (honestly!) He recently wrote a paper after studying students’ omission errors at a photocopying machine:

Combating Omission errors through task analysis and good reminders J. Reason

Reason correctly predicted that the most frequent photocopying omission error (15 others were classified) would be to leave the last page of the original in the photocopier because it met four error provoking conditions:

1/The closed lid concealed the last sheet2/ the emergence of the last sheet is a false completion signal, 3/ This false completion signal comes at the end of a boring job when you are naturally thinking of the next task, 4/ removing the last page of document is now a functionally isolated act, because up to that point the removal of a document page was cued by the need to put in the next page.

Here’s a full list of some characteristics of error provoking tasks

Error Provoking Tasks

  • Those carried out when we are distracted, stressed or under pressure.

  • Those in which strongly habitual actions interfere with our intended action e.g. The capture error above which involved a planned departure from the usual route.

  • Technology related Mode errors. A whole new kind, often incorporating poor machine design with human error: e.g. Getting the num Lk button stuck on and wondering why y64 are ty*5ng r4bb5sh ? Or trying to take the lid of the food mixer when it’s locked in programme set mode.

  • When the step is very demanding on working memory.

  • Steps in which the object is hidden from view(e.g. last page of original document in a photocopier)

  • Repetitive steps are prone to omission e.g. transferring figures to accounts.

  • Steps following interruption- you lose your place in the action sequence.

  • Steps that are isolated- i.e. Are not necessarily cued by the previous steps.(see photocopier again)

  • Steps that are triggered by weak or ambiguous signals e.g. point of jam set in jam making.

Error Reduction

- Redesign

So you know what tasks are error provoking, how can you prevent errors?

Occasionally it’s possible to redesign your workspace to eliminate an irritating error. ur. E.g. you make tea more often then coffee. When you want coffee you automatically make yourself tea. Using a coffee making machine so that the tasks are separated might help.

Or to redesign a task- could you have taken a route to the cinema that did not involve a part drive on the habitual route to work?

-Use of Reminders

  • Notes and Post its
  • Diaries
  • Lists
  • Writing on back of hand
  • Ask for reminder from others
  • Calendars, timetables
  • Clocks and alarms
  • Mental checking- routinely running thru the days tasks mentally on waking or before sleeping
  • Forming associations- links items, actions to be remembered to places or objects
  • Visualising- imaging the thing to be remembered or rehearsing the whole action-
  • Finally not on the Professors list, but I’d add mindfulness training

A little more on Visualisation

I suspect the last 4 techniques , being action/perception oriented ,can be powerful for ADHD ers.

I’ve recently started using visualising, it’s effective for me, and has the further beauty that there are no things to keep track of: no paper, notebooks or gadgets

For example

When I go into Brussels, I change from the 44 at Montgomery on to the Erasmus metro or less often, Tram 90. I’ve sometimes found myself boarding the Erasmus metro when I should be on tram 90(the better rehearsed sequence capturing the action.)

So Now on the way to catch the 44 I flash a brief image( a millisecond only no need to stress it) of myself walking past the ticket machines at Montgomery looking for the 90 /93 sign, I refresh the image briefly every time my journey destination crosses my consciousness. Adding sensory reminders also helps, the Bruxellois smell of the waffle booth, the dismal sound of muzak...

I’ll let you know if I catch the wrong tram again!

Visualisation can be extended to mental rehearsal of a whole action sequence you want to get right such as;-

-the timing of actions in cooking an ambitious meal.

Emotionally demanding scenarios may be usefully rehearsed;

-Working through coping when Uncle John gets drunk at Christmas (picture things getting out of hand, yourself engaged in effective damage limitation without getting upset-)

-a difficult interview with your boss

if you want to read more search on using imagery and visualisation in Sport science.


Characteristics of a Good Reminder- The Five C’s

  • Conspicuous – to Catch attention
  • Contiguous -Positioned at location and time of necessary action
  • Context –Cues when and where the action should be remembered
  • Content- Sufficient information about task
  • Count-able to tick off the number of actions as they are performed

Web Link: Why we make mistakes

Finally ,Errorsss6s can never be completely eeliminated!

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