Retention of memories

1
Retention of memories

• The retention function
• Spacing effects
• Interference and repression

2
I. Forgetting

• Forgetting is the obverse of retention
• Three theories of forgetting
• Decay hypothesis
• Interference hypothesis
• Retrieval-cue hypothesis

3
II. The retention function

• Ebbinghaus and Peterson Peterson
• The power law of forgetting
• More negatively accelerated than exponential
  functions
• Forgetting is very slow
• Savings, p(recall), and retrieval time all fit
  the power law
• Decay hypothesis seems to be supported

4
Practice effects on forgetting

• Practice does not affect the rate of forgetting
• Practice does affect the amount recalled after a
  particular length of delay

Amount recalled
More practice
Less practice
Time?
5
Why a power function?

• The strength equation (power law of remembering)
  approximately fits the frequency and recency with
  which information occurs in the environment
• Fits New York Times headlines, e-mail messages,
  and parents comments to children

6
III. Spacing effects
0

• Continuous paired-associates (Glenburg, 1976)
  Study interval and test interval
• bank-tail
• fish-home
• fish-???
• bank-tail
• pail-nose
• frog-girl
• pail-???
• snow-ball
• bank-???

7
Glenbergs (1976) results
0
Test Interval 2 items 8 items 32 items 64 items
Proportion recalled .2 .3 .4 .5
.6
0 1 4 8 20
40
Spacing (Number of events between presentations
8
Interpretation Study interval should match
retention interval
0

• In short study intervals, the second presentation
  is forgotten
• Hintzman, Block, and Summers (1973) presented
  information twice, but in two sensory modalities,
  to see which was forgotten.
• Spacing effects in the environment Massed items
  are forgotten (flash in the pan effect)
• Compare with CRF extinction effect

9
IV. Interference
0

• Negative transfer Learning
• Proactive interference Forgetting
• Retroactive interference Forgetting
• Multiple associations to the same cues maximizes
  interference
• Sharing associative value Rescorla-Wagner

10
More interference
0

• Recognition memory tasks
• Anderson (1974)
• Occupations x locations
• Recognize probes among detractors
• Speed of recognition is inversely related to the
  number of sentences per probe Fan effect
• Activation equation
• Record activation Record strength
  Sum(Association strengths)

11
V. ACT-R and SAM theories
0

• Adaptive Character of Thought (Anderson, 1996)
  Procedural and declarative knowledge interact to
  yield complex cognition
• Knowledge units underlie cognition
• Procedural knowledge production rules
• Declarative knowledge chunks.
• Chunks are formed following production rules
  structured in the environment.
• Spotlight metaphor of chunking

12
SAM theory
0

• Search of Associative Memory (Raaijmaker
  Shiffrin, 1980)
• Memory is searched by retrieval cues
• Category names
• Context cues
• List cues

13
VI. Repression
0

• Context effects on memory
• State-dependent recall
• Mood-dependent recall
• Emotional blocking Encoding, rehearsal, or
  repression?

14
Arousal and retention Reminiscence
0

• Low-arousal learned items recalled better at
  short intervals
• High-arousal learned items recalled better after
  delay
• Usually not increased memory for high-arousal
  learned items, but less forgetting than for low
  arousal learned items.
• Stimulant drugs improve memory
• High arousal times of day improve memory

15
Eyewitness memories
0

• Inaccuracy is disturbing
• Weapon focus hypothesis
• Yerkes-Dodson Law
• Flashbulb memories are intense
• O.J. Simpson verdict (Schmolk, Buffalo Squire,
  2000)
• MacKay Ahmetzanov, 2005
• False memories
• Key variable Focusing of attention

16
Record activation (Anderson, 1974)
0
Teacher Houghton Student Fillmore Sailor
Scio
Student in Fillmore
Teacher in Houghton
Sailor in Scio
Sailor in Houghton