Remember to take the cake out of the oven: A model for timebased prospective memory

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Remembering to take the cake out of the ovenA
model for time-based prospective memory

• Igal LeshemNoam MorDorit YadidAvi Goldstein

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What is prospective memory?

• Realization of delayed intentions
• Delivering a message next time we meet a friend
• Remembering to take a medicine, or take the cake
  out of the oven
• Subject is not prompted to remember, but has to
  remember to remember

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What is prospective memory?

• Very common task in daily life
• Socially important
• Requires Self-Initiation
• Adherence
• Low correlation with retrospective memory
  measures

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Two types of prospective memory (Einstein
McDaniel, 1990)

• Event-based prospective memoryExternal event is
  cue
• friends face prompts memory of message
• Time-based prospective memoryAction to be
  performed at a specific time No external
  cuesTime has to be monitored

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Prospective memory in the lab

• Subject is engaged in an ongoing task
• Instructed to perform a different action when an
  special event occurs
• Example While naming faces on screen, press a
  button
• when face has moustache (event)
• every 5 minutes (time)

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Time-based prospective memory

• No obvious external cues Success dependent on
  monitoring time during a critical period
• Self-initiation
• Probably very different processes involved in
  short-term and long-term tasks
• Focus here is in short-term tasks (minute range)

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Time-based prospective memory

• Current model is behavior-descriptive
• Test-Wait-Test-Execute (Harris Wilkins, 1982)
  after TOTE (Miller et al., 1960)
• Model does not identify the mechanisms underlying
  this type of behavior

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Time-based prospective memory

• Harris Wilkins (1982)
• J-shaped function of clock checks

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Variables affecting TBPM

• Age (Einstein et al. 1995 Martin, Kliegel,
  McDaniel, 2003 Maylor et al. 2002 Park et al.,
  1997) but not in naturalistic studies (Maylor,
  1990 Rendell Thomson, 1993, 1999)
• Importance (Cicogna Nigro, 1998 Kliegel et
  al., 2001 Kvavilashvili, 1987)
• Ongoing task demands (Park et al., 1997
  d'Ydewalle, 2001 Logie et al., 2004 Martin
  Schumann-Hengesteler, 2001)

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Time perception in TBPM

• Since no external cues, then the feeling of
  passing time might be what prompts intention
  retrieval and clock checking
• How are clock-monitoring and PM accuracy
  influenced by the perception of the passage of
  time?
• Is time-monitoring necessary / sufficient?

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Aims

• Examine the effects of ongoing task demands and
  time-perception on the various facets of PM
• Individual differences in time-management and
  time-estimation

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Method

• Ongoing task / prospective task paradigm
• Two variables were manipulated
• difficulty of ongoing task (memory load)
• clock speed (normal, 30 faster)
• Measures timing of PM response, number and
  timing of clock checks

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Method

• Ongoing taskSubjects memorized words that were
  presented every 2-4 seconds on a computer
  screenAt random intervals they were asked to
  repeat the last 3 (low memory load) or 5 (high
  load) words

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Method

• Prospective memory taskSubjects were instructed
  to press a certain key on the keyboard exactly
  every 7 (normal clock) or 9 (fast clock) minutes
• 2 PM trials per subject
• Subjects could check the time elapsed freely. A
  digital clock was displayed briefly by clicking
  the computer mouse

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Method

• Individual-differences variables
• Time Management Behavior Scale (Macan et al.,
  1990)
• Perceived control of time
• Setting goals/ priorities
• Scheduling
• Time estimation
• Production of 1 minute intervals

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Method

• 108 subjects (64 men, 44 women, age 19-32)
• randomly assigned to one of four conditions
  low/high load, normal/fast clock
• Tested individually, without wrist watches, in a
  noise-attenuated room

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Results Ongoing task

• Recall was higher for the low-load memory task
  than for the high-load task (89 vs. 77, plt0.01)
• Recall was higher for the normal-clock condition
  than for the fast-clock condition (89 vs. 80,
  plt0.01)

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Results PM success

• Mean delay of PM response (seconds)

Load plt0.01, Clock speed NS., Load X Clock
speed plt0.05
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Results clock checking

• Mean number of clock checks per trial

Load plt0.01, Clock speed plt0.001
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Results clock checking

• Mean number of clock checks of each group (per ¼
  of period)
• Clock speed had an effect early in the task,
  while load had an effect only at the end

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Results Individual differences

• High TMB scorers checked the clock more often
  under fast-clock conditions r0.43, plt0.001, but
  not under normal clock (r0.08,ns)
• Ss that underestimated time were less accurate in
  PM responses, r-0.41, plt0.01
• Ss that underestimated time checked the clock
  more often, r-0.46, plt0.001

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Summary

• Differential effects on monitoring
• Clock speed ? first part of period
• Task load ? last part of period
• ? Calibration vs. resource allocation
• Effects on accuracy
• Task load ? reduced accuracy
• Clock speed ? depending on load
• Lapses of intention (late responses occuring
  after checking the clock very close to target
  time) occurred 3 times more under high-load
  conditions

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Summary

• Individual variables increased accuracy
• High TMBs increased checks,good estimators less
  checks
• Time-managers allocated more resources to
  monitoring, good estimators succeeded with
  economic monitoring

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Conclusions

• PM performance requires independent operation of
  time-monitoring and intention-maintenance
  mechanisms

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Provisional model

• 3 independent components
• Time-monitoring process
• Involves feeling of time
• Under normal conditions optimal checking
  strategy, minimally interrupting ongoing task
• Allows calibration by changing rate
• Planned nature
• Prospective time

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Provisional model

• Maintenance of intention
• Keeps intention in WM for a sufficient time to
  carry it ouy
• Resource demanding
• Most vulnerable to task demands
• Cued intention-retrieval
• Triggered by subtle internal or external cues,
  reminders
• Intention supperiority effect
• Can result in clock-check (retrospective time),
  or start monitoring component

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encoding
target time-window
cued retrieval
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encoding
target time-window
cued retrieval
pulse
step
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Thank you for your time
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