Prospective Memory in Aviation: Understanding Memory Errors in Everyday Tasks

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 B737—widely 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. Varieties of PM (1) Episodic Tasks • 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. Varieties of PM (2) Habitual Tasks • Most cockpit tasks are habitual • Many tasks must be performed, many with multiple steps • Normally performed in set sequence by SOP • Execution becomes largely automatic—deliberate search of memory not required • Explicit (episodic) intention not required—intention 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. Varieties of PM (2) Habitual Tasks • Most cockpit tasks are habitual • Many tasks must be performed, many with multiple steps • Normally performed in set sequence by SOP • Execution becomes largely automatic—deliberate search of memory not required • Explicit (episodic) intention not required—intention 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. Varieties of PM (3) Atypical Actions Substituted for Habitual Actions • 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. Varieties of PM (4) Interrupted Tasks • 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. Varieties of PM (5) Interleaving Tasks, Including Monitoring • 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. Varieties of PM (5) Interleaving Tasks, Including Monitoring • 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 task—very 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. An Experimental Study of Interruptions Experimental Paradigm • 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 abrupt—current 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. An Experimental Study of Interruptions Experimental Paradigm (continued) • 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. An Experimental Study of Interruptions Encoding Manipulations • 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. An Experimental Study of Interruptions Retrieval Manipulations • 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. An Experimental Study of Interruptions Summary of Results

22. An Experimental Study of Interruptions Implications • 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/flightcognition