Crosstask Prediction of Working Memory Performance: Working Memory Capacity as Source Activation - PowerPoint PPT Presentation

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Crosstask Prediction of Working Memory Performance: Working Memory Capacity as Source Activation

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New Work: The n-back task. Subjects view a long sequence of letters ... 2-back - letter is a target if it matches the letter before the previous one ... – PowerPoint PPT presentation

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Title: Crosstask Prediction of Working Memory Performance: Working Memory Capacity as Source Activation


1
Cross-task Prediction of Working Memory
PerformanceWorking Memory Capacity as Source
Activation
  • Larry Z. Daily, Marsha C. Lovett, and Lynne M.
    Reder
  • Carnegie Mellon University
  • Thanks to Scott Filipino for assistance in
    collecting the data.
  • This work supported grant F49620-97-1-0455 from
    the Air Force Office of Scientific Research and
    grant N00014-95-1-0223 from the Office of Naval
    Research.

2
Working Memory in ACT-R
  • Provides the resources needed to retrieve and
    maintain information during cognitive processing
    (Baddeley, 1986)
  • Working memory capacity is limited
  • W is limited (Anderson, Reder, Lebiere, 1996)
  • Working memory limits vary across individuals
  • W varies over individuals (Lovett, Reder,
    Lebiere, 1999)

3
Prior WorkThe MODS Task
  • MOdified Digit Span
  • Read strings of digits and letters aloud
  • Remember the numbers
  • Memory set size varied from 3 to 6

4
MODS TaskAggregate Results
5
MODS TaskIndividual Accuracy
6
MODS TaskIndividual Serial Position
7
CAM InductiveReasoning Subtest
8
Cross-task Correlations
  • Estimates of W strongly correlated with scores on
    CAM inductive reasoning subtest
  • r 0.50 r2 .25
  • Correlations are a weak test of Ws predictive
    ability
  • No model of the CAM

9
New WorkThe n-back task
  • Subjects view a long sequence of letters
  • For each, indicate whether it is a target or
    non-target
  • Targets defined by condition
  • 0-back - target is a letter given at the start
  • 1-back - letter is a target if it matches the
    previous letter
  • 2-back - letter is a target if it matches the
    letter before the previous one
  • 3-back - letter is a target if it matches the
    letter 3 before the current one

10
N-back Strategies
  • Familiarity-based
  • Subjects use familiarity to decide whether an
    item is a target
  • Doesnt depend on W
  • Update
  • Subjects actively try to maintain a list of prior
    items
  • Does depend on W
  • We model this

11
The n-back Model
  • Encodes the item currently in vision
  • Memory chunk encodes item and position
  • Attempts to match the item to a stored memory
  • Looks for a memory chunk with a position that
    matches the n-back condition and the correct item
  • Sets a flag to indicate match or not

12
The n-back Model
  • Responds
  • Target or non-target based on flag
  • Updates memory chunks
  • Changes the position of each chunk up through the
    current n-back condition
  • If this process fails, several responses required
    to get back on track

13
Aggregate Results
14
Individual ResultsMODS Task
15
Individual ResultsMODS Task
16
Individual ResultsN-back Task
17
Individual ResultsN-back Task
18
Conclusions
  • Varying W captures differences in individuals
    working memory performance.
  • W can be used to predict performance across
    tasks.
  • W is a workable measure of working memory
    capacity.
  • ACT-R can be fruitfully applied to the study of
    individual differences.
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