Prospective Memory in Aviation, Everyday Tasks, and the Laboratory Key Dismukes Human Systems Integration Division NASA Ames Research Center Moffett Field, CA Psychonomic Society 18 November 2006

1
Prospective Memory in Aviation, Everyday Tasks,
and the LaboratoryKey DismukesHuman Systems
Integration DivisionNASA Ames Research
CenterMoffett Field, CAPsychonomic Society18
November 2006

2
Major U.S. Airline Accidents Involving
Inadvertent Omission of a Normal Procedural Step
(1987-2001)

• Five of 27 major accidents in which NTSB found
  crew error to be a causal factor
• 1988, Detroit DC-9-82 Flaps/slats not set to
  takeoff position,154 killed 1 seriously injured
• 1989, Dallas-Ft Worth B727 Flaps/slats not set
  to takeoff position, 14 killed 5 seriously
  injured
• 1995, LaGuardia MD-82 Pitot-static heat not
  turned on, aircraft destroyed, no
  fatalities/serious injuries
• 1997, Houston DC-9 Hydraulic boost pumps not set
  to high before landing, aircraft badly damaged,
  no fatalities/serious injuries
• 2001, Little Rock MD-82 Spoilers not armed
  before landing, 11 killed 110 injured
• Multiple factors involved, but a central aspect
  was experienced pilots forget to perform a
  normal, highly-practiced procedural step

3
Theoretical Accounts of Prospective Memory Still
in Infancy

• Our view of evidence
• After intention for deferred action is formed,
  attention turns to other tasks
• Deferred intention fades from WM but remains in
  LTM
• Retrieval requires noticing some cue associated
  in memory with intention
• Can be environmental cue or stream-of-thought cue
• Stored intention is retrieved if sufficient
  activation spreads to it from cue

4
Linking Real-World PM Phenomena to Underlying
Cognitive Processes

• Three complementary approaches
• Ethnographic
• Analyses of accident/incident reports
• Laboratory studies
• Structure of airline operations well suited to
  study of skilled performance error
• Operations are highly standardized
• Can observe deviations from formal SOPs
• Fair consensus about appropriate/inappropriate
  actions

5
An Ethnographic Study(Loukopoulos, Dismukes
Barshi, in preparation)

• Focused on B737widely used in air transport
• Reviewed written operating procedures,
  participated in classroom and flight simulation
  training at two major airlines
• Observed large number of flights from cockpit
  jumpseat in normal revenue flights

6
Some Findings from Ethnographic Study

• Pilots are
• Frequently interrupted
• Forced to postpone planned tasks
• (Each) forced to perform multiple tasks in
  parallel
• Timing and nature of task demands is not entirely
  predictable and is only partly under control of
  the crew
• These results confirmed by a study analyzing NTSB
  reports of the 19 major U.S. airline accidents
  attributed primarily to crew error 1990-2001
  (Dismukes, Berman, Loukopoulos, in press)

7
Memory Errors Reported to the Aviation
Safety Reporting System (Nowinski, Holbrook,
Dismukes, 2003)

• Sampled 20 of air carrier reports over 12-month
  period
• Selected reports clearly involving some type of
  memory error
• 74 of 75 reports involved prospective rather than
  retrospective memory
• Does not necessarily indicate PM more common than
  RM failures, but suggests PM failures may be
• more consequential
• more likely to be reported
• and/or more common

8
Varieties of Prospective Memory in the Cockpit

• In these three studies analyzed
• What tasks were being performed concurrently
• Whether forgotten task was habitual
• What cues would normally be present to trigger
  retrieval
• Whether those cues were actually present
• Concluded PM demands emerge in five types of
  situation
• Episodic tasks
• Habitual tasks
• Atypical tasks substituted for habitual actions
• Interrupted tasks
• Interleaving tasks, including monitoring

9
(1) Episodic Tasks
Varieties of PM

• Tasks not performed habitually
• Type of PM task most often studied experimentally
• Example ATC instructs crew to report passing
  through 10,000' during descent
• In real world, ongoing tasks often divert
  attention from cues that might trigger retrieval
  (Holbrook, Dismukes Nowinski, 2005)
• May be a major source of variance, but not
  studied extensively
• This is the type of task studied most often in
  laboratory paradigms

10
(2) Habitual Tasks
Varieties of PM

• Most cockpit tasks are habitual
• Many tasks must be performed, many with multiple
  steps
• Normally performed in set sequence by SOP
• Execution becomes largely automaticdeliberate
  search of memory not required
• Explicit (episodic) intention not
  requiredintention is implicit in action schema,
  stored as procedural memory
• Performance of habitual tasks normally quite
  reliable
• Performance undermined if normally present cues
  are removed
• Example Setting flaps to takeoff position is
  deferred because of freezing slush on taxiway
• Action out of sequence removes normal cues
  normal context
• Habitual task becomes episodic task, but pilots
  may not realize need to encode explicit intention

11
(2) Habitual Tasks
Varieties of PM

• Most cockpit tasks are habitual
• Many tasks must be performed, many with multiple
  steps
• Normally performed in set sequence by SOP
• Execution becomes largely automaticdeliberate
  search of memory not required
• Explicit (episodic) intention not
  requiredintention is implicit in action schema,
  stored as procedural memory
• Performance of habitual tasks normally quite
  reliable
• Performance undermined if normally present cues
  are removed
• Example Setting flaps to takeoff position is
  deferred because of freezing slush on taxiway
• Action out of sequence removes normal cues
  normal context
• Habitual task becomes episodic task, but pilots
  may not realize need to encode explicit intention

12
(3) Atypical Actions Substituted for Habitual
Actions
Varieties of PM

• Example Crew often departs from an airport via a
  Standard Instrument Departure requiring left turn
  to 300 degrees at 2000 feet
• Execution of procedure becomes largely automatic
• If ATC on one occasion amends instruction to turn
  left to 330 degrees at 2000 feet
• Crew must form episodic intention to turn to 330
  and must inhibit normal response to level out at
  300 degrees
• When busy with other tasks, crews vulnerable to
  habit intrusion (Reason, 1984) and level out
  prematurely at 300

13
(4) Interrupted Tasks
Varieties of PM

• Interruptions very common in cockpit
• Duration lasts from seconds to minutes
• Interruptions are often so abrupt and salient
  that pilots may do little to encode explicit
  intention to resume interrupted task
• Common error is to deal with interruption then
  proceed to next task, forgetting to complete
  interrupted task
• Cockpit does not always provide salient cues for
  status of interrupted tasks
• Perceptually rich cockpit environment associated
  with many tasks remaining to be performed

14
(5) Interleaving Tasks, Including Monitoring
Varieties of PM

• While performing ongoing tasks pilots must
  periodically monitor status of other tasks, e.g.
• While running checklists, communicating,
  programming, etc., First Officer must monitor
  progress of taxi by Captain
• Monitoring is important, but difficult to
  maintain monitoring goal in WM as dual task if
  event rate low
• Similar to difficulty with vigilance
  (Parasuraman, 1986) but different
• Must interrupt ongoing task and shift attention
• Attention allocated preferentially to areas with
  high info content over monitoring for low
  probability events, albeit with high consequences
  (see Wickens et al., 2003 for attention
  allocation model)
• When attention shift delayed, monitoring task may
  slip from WM must be retrieved, as in other
  forms of PM

15
(5) Interleaving Tasks, Including Monitoring
Varieties of PM

• While performing ongoing tasks pilots must
  periodically monitor status of other tasks, e.g.
• While running checklists, communicating, etc.,
  First Officer must monitor progress of taxi by
  Captain
• Monitoring is important, but difficult to
  maintain monitoring goal in WM as dual task if
  event rate low
• Similar to difficulty with vigilance
  (Parasuraman, 1986) but different
• Must interrupt ongoing task and shift attention
• Attention allocated preferentially to areas with
  high info content over monitoring for low
  probability events, albeit with high consequences
  (see Wickens et al., 2003 for attention
  allocation model)
• When attention shift delayed, monitoring task may
  slip from WM must be retrieved, as in other
  forms of PM

16
An Experimental Study of Interruptions(Dodhia
Dismukes, submitted)

• From aviation studies, hypothesized individuals
  forget to resume interrupted tasks largely
  because
• Salient intrusion of interruptions diverts
  attention, discouraging encoding explicit
  intention to resume or identifying specific
  reminder cues
• Resumption will depend on happening to notice
  cues previously associated with interrupted
  taskvery unreliable
• Cues indicating opportunity to resume interrupted
  task may not match form of (implicit or explicit)
  encoded intention
• End of the interruption is not a discrete
  perceptual cue but a state of affairs requiring
  interpretation
• Poor match between cues and encoding provides
  little activation to retrieve intention from LTM
• End of interruption often followed by other task
  demands that divert attention from interpreting
  significance of completing interruption
• New task goals spread activation to task subgoals
  rather than to retrieving implicit goal of
  resuming interrupted task

17
Experimental Paradigm
An Experimental Study of Interruptions

• Participants answer questions resembling SAT,
  Category of questions changed between blocks
• Instructed that when blocks were interrupted they
  should remember to resume interrupted block after
  completing interruption before starting new block
• In baseline condition interruptions were
  abruptcurrent screen replaced with screen of
  different color and with different category of
  questions
• After each completed block a screen appeared for
  2.5 sec Loading next block, followed by next
  block in series

18
Experimental Paradigm (continued)
An Experimental Study of Interruptions

• Without explicit prompt participants had to
  remember to return to interrupted block
• Proportion of successful resumptions of
  interrupted task in baseline condition 0.48

19
Encoding Manipulations
An Experimental Study of Interruptions

• Hypothesis 1 Intrusion of sudden interruption
  discourages adequate encoding of explicit
  intention to resume interrupted task
• Tested with encoding reminder manipulation
• Interruption began with 4 sec message Please
  remember to return to the block that was just
  interrupted
• Results Performance increased from 0.48 to 0.65
  (proportion of interrupted blocks resumed)
• Was improvement due to reminder or to 4 sec delay
  before beginning interrupting task? Tested with
  encoding pause manipulation
• Interruption began with 4 sec blank screen
• Results Performance increased from 0.48 to 0.65
• Conclusion Pause before beginning interrupting
  tasks helps remember to resume interrupted task

20
Retrieval Manipulations
An Experimental Study of Interruptions

• Hypothesis 2 Individuals are likely to forget to
  resume interrupted tasks because of mismatch
  between form of encoded intention and diverse
  cues that must be interpreted to recognize
  interruption has ended
• Tested with retrieval reminder manipulation
• 2.5 sec Loading next block screen also said
  End of interruption
• Results Performance increased from 0.48 to 0.90
  (proportion of interrupted blocks resumed)
• Hypothesis 3 Individuals are likely to forget to
  resume interrupted tasks if interrupting task is
  directly followed by other tasks that demand
  attention
• Tested with retrieval pause manipulation
• Interval between end of interruption and
  beginning of next block increased to 8-12 sec and
  countdown clock appeared on screen
• Results Performance increased from 0.52 to 0.88
  (proportion of interrupted blocks resumed)

21
Summary of Results
An Experimental Study of Interruptions
22
Implications
An Experimental Study of Interruptions

• Theoretical
• Supports three hypotheses but more research
  needed
• Consistent with model of PM in which intentions
  are retrieved from LTM by activation from cues
  processed attentively
• Practical
• Pausing before dealing with interruptions to
  explicitly encode intention to resume interrupted
  task and to identify specific reminder cues
• Periodically pausing after completing tasks to
  ask what other tasks remain to be done

23
Final Thoughts

• Prospective memory probably operates in similar
  ways in the skilled tasks performed by other
  kinds of experts, e.g., medical personnel
• To be effective, countermeasures to PM errors
  must be realistic for experts to apply while
  performing their task
• Understanding the real-world performance requires
  integrating diverse research approaches,
  including observing real-world performance and
  well-controlled experimental studies
• This integrative approach enhances the power of
  both field and lab studies

24

• Thanks to my colleagues in this research
• Rahul Dodhia, Jon Holbrook, Kim Jobe,
• Loukia Loukopoulos, and Jessica Nowinski
• For more information
• http//human-factors.arc.nasa.gov/ihs/flightcognit
  ion