Key Dismukes, PhD

Chief Scientist for Aerospace Human Factors

NASA Ames Research Center

12 January 2002

Lessons from Aviation: Memory, Skilled Human Performance,

and All-too-human Error

Road Map of Talk

A cognitive perspective on error   vulnerability of skilled professionals

Examples from one domain of error:   prospective memory– Lapses in everyday life

– Lapses in flight operations

Implications for professional training

Most Airline Accidents Attributed to Crew Error

Society: error = blame– Misrepresents nature of cognitive skill

– Undercuts safety

Research on human factors in aviation safety– Extrapolate to other professional domains?

Aircrew Performance

Trained to high level of performance; daily practice; annual recurrent training

Monitored periodically by check pilots

Highly motivated

NTSB accident reports reveal few examples of incompetence or malfeasance

Two Fallacies about Error

Fallacy: Error can be eliminated if pilots are sufficiently  vigilant, conscientious, and proficient.

Truth: Vigilant, conscientious experts routinely make errors.

Fallacy: If an accident crew made errors in tasks that pilots routinely handle without difficulty, that accident crew must have been in some way deficient — either they lacked skill, or had a bad attitude, or just did not try hard enough.

Truth: The fallacy ignores sampling bias. No matter how many times an expert performs a procedure perfectly, the probability of error is greater than zero.

A Cognitive Perspective

Simply trying hard will not prevent errors

Unique human capabilities enabled by biological information-processing mechanisms– Vulnerable to error

Error is probabilistic, not deterministic

Illustrate with research on memory errors

Prospective Memory (PM)

Remembering to perform an action that  must be delayed

Relatively new field of human memory  research

Defining characteristics:– Delay between forming intention and opportunity to   execute

(seconds to years)

– Delay filled with other tasks that occupy attention

– No explicit prompt telling us it is time to execute intention

So how do we ever remember to perform   intentions?

– A theoretical perspective

Attributes of the Model

Mem

ory

More accessib

le

Activatedrepresentations

Activation

• Very limited capacity• Currently attended representations• Dynamic flow of contents• Representations compete to enter attention based on level of activation

External Stimuli

Less acce ssib

l e

Long-term memory• very large capacity

Focal Attention

Attributes: Activation and Retrieval of Memory Representations

Mem

oryM

ore accessible A

ctivation

“horse”

External Stimuli

Less acce ssib

l e

Long-term memory

Focal Attention

cowboy

saddle

Indian

racing

animal

“horse”

horse

Currently attended representation

provides activation to associated item

in memory Activation increases as function of

time in attention Activation decays as function of time

since last attended Activation is finite and divided among

associates Activation is divided according to

strength of links to associate

More accessib

le

Attributes: Goals are Memory Representations

Mem

oryM

ore accessible

Activation

prepare vuegraph

External Stimuli

Less acce ssib

l e

Long-term memory

Focal Attention

preparetalk

scheduleconference

room

flossdaily

win Nobel prize

Deferred intentions are a form of goal Goals are represented as condition/action

associates (If…then) Goals are associated in hierarchies of sub-

goals Sub-goal in focal attention helps maintain

activation of higher goal

More accessib

le

Einstein-McDaniel PM Paradigm

Instruct subjects to perform cover task   (e.g., reading a paragraph or rating pleasantness of   series of words)

  Give additional (PM) task   (e.g., “Press slash key when see a name of an animal”)

  Subjects begin performing cover task

–   Delay between starting cover task and trial with   animal name

–   Must remember to perform PM task without   prompting

Prospective Memory as Competing Concurrent Task

Mem

oryM

ore accessible A

ctivation

lion

External Stimuli

Less acce ssib

l e

Long-term memory

Focal Attention

cub

lion

lion

ratepleasantness

Africa

catParticipate

in experiment

animal

presskey Prospective task

competes with pleasantness rating for retrieval

On-going task has inherent advantage

Outcome is probabilistic

Depends on multiple factors

More accessib

le

Implications for Real-World Performance

Cannot maintain delayed intentions in   focal attention

– Must retrieve from memory when opportunity for   execution arises

– Retrieval requires noticing some cue associated   with intention

– Availability of cues and noticing cues is haphazard

Thus, memory lapses are commonplace

Strategies

Importance of delayed intention does not   prevent memory lapses

Simply trying harder is ineffective

Strategies may help to some degree:– Habitual review: what do I need to do now?

– Encode environmental cues likely to be present in window of opportunity for execution

– Create salient cues that must be processed during ongoing task

Cockpit operations are highly proceduralized

Taxi, climb out, descent, and arrival are sometimes quite busy

Each pilot is responsible for multiple concurrent tasks (e.g., searching for traffic and flying the airplane)

Interruptions, distractions, or preoccupation with one task to the detriment of another found in nearly half of NTSB accident reports

Issue may be management of attention rather than overload

Flight Crews Manage Multiple Tasks Concurrently

Lapses in monitoring (2/3 of reports)

– Aircraft position: taxi, altitude capture, navigation

– Aircraft status: systems, automation

– Actions of other crew member

Lapses in prospective memory (1/4 of reports)

– Complete interrupted procedure on checklist

– Retract speed brakes when leveling-off descent

– Reset flaps and bleed air after de-icing

– Stop fuel transfer

– Set take-off flaps when deferred

– Defer lowering landing gear in minimum fuel situations

Examples of Neglected Tasks

Aviation Incident Study

Competing Tasks that Distracted or Preoccupied Pilots

50% involved communication (e.g., conversation with other crewmembers/flight attendants, radio communication, ATIS, PAX announcements).

16% involved “head-down” tasks (e.g., paperwork, FMS entry, reviewing charts)

14% involved abnormals

8% involved searching for/responding to traffic

12% miscellaneous (e.g., decision-making, unstabilized approach)

Aviation Incident Study

Lapses in monitoring (2/3 of reports)

– Aircraft position: taxi, altitude capture, navigation

– Aircraft status: systems, automation

– Actions of other crew member

Lapses in prospective memory (1/4 of reports)

– Complete interrupted procedure on checklist

– Retract speed brakes when leveling-off descent

– Reset flaps and bleed air after de-icing

– Stop fuel transfer

– Set take-off flaps when deferred

– Defer lowering landing gear in minimum fuel situations

Examples of Neglected Tasks

Aviation Incident Study

Omitting a Procedural Step

Highly practiced procedures vulnerable to omission when:– Interrupted

– Performed outside normal sequence or context

Highly practiced procedures become largely automatic– Allows fast, smooth execution

– Requires minimal conscious supervision

– Execution largely under control of environmental cues

Most common error in maintenance: omitting a step in re-assembly– Example: finish tightening spark plugs

Why So Easy to Forget a Procedural Step?

With highly practiced procedures, retrieval of each step triggered by:– Current state of environment

– Execution of immediately preceding step

Interruption breaks chain of preceding steps -- no trigger

Environment may seem to indicate uncompleted step has been performed

No episodic memory trace for habitual actions

Omitting a Procedural Step

Prospective Memory Countermeasures

Recognize the threat– Vulnerable even when tasks are important and delays are short– Especially vulnerable: Interruptions and performing habitual procedures

out of normal sequence

Explicitly note interruption and identify when/where intention will be executed– In team situation, say aloud

Create salient reminder cues*

Avoid rushing procedures

Periodically review status and ask if anything is missing

Use checklists** Not always practical

Training Implications

Line Oriented Flight Training (LOFT)

Full-mission simulation

Normal operations and challenging situations (e.g., weather diversions, equipment failures)

Should include realistic:– Concurrent task demands

– Interruptions

– Distractions

– Delays

Training Implications

Error Management Training

Change in historic attitude

Errors are inevitable

Training should address:

– Recognizing potential threats

– Detecting errors

– Managing error outcome

Training Implications

Error Data from Routine Operations

What errors occur, circumstances, and how professionals respond

Accident/incident reports useful but are a limited and biased sample

LOSA: Line Operational Safety Audits– Large sample of daily operations

– Data on threats, errors, and how crews manage

– Comprehensive and realistic picture of challenges

LOSA + laboratory research   powerful new approaches to training

Training Implications