Temporal Spacing of Learning:Can It Help Reduce Forgetting?
Hal Pashler
University of California, San Diego
Dept of Psychology
Power Function
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Study-Study
0.92(.04t + 1)-1.63
0.87(.04t + 1)-1.58
Forgetting: A Classic Topic in Experimental Psychology
Forgetting in K-12 Education
• Educational failure may often reflect forgetting as well asabsence of initial mastery.
• Summer Vacation Set-backs
• “Regression” to partial understanding and initial misunderstandings (Bob Siegler).
“People who went to college can tell you what they learned in just 5 minutes. So, at my college, students learn just the same stuff – all in 5 minutes.”
Father Guido Sarducci’s
5-Minute College
Our Research Aim:
Identify procedures that
• can readily be applied in educational contexts.
• reduce rate of forgetting
2. Temporal Distribution of Study Sessions
4. Form and Timing of Feedback
1. Temporal Distribution of Practice within Study Sessions
3. Overlearning
Topics
5. Testing Effects
Analyzing Temporal Distribution of Study Sessions
Time
StudySomething
Once
StudyIt
AgainTest
Inter-study Interval (ISI)
Retention Interval (RI)
• Scarcely any application in classroom or instructional technology
• Huge Literature showing poor learning with very short ISI (“spacing effect”)
Spacing Research with Significant Retention Intervals (> 1 day)
14 papers
(Many with serious methodological problems)
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Inter-Study Interval (days)
Pe
rce
nt
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rre
ct
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ca
llAusubel (1966)
Childers & Tomasello (2002)
Childers & Tomasello (2002)
Edwards (1917)
Edwards (1917)
Glenberg & Lehmann (1980)
RI = 6 days
RI = 7 days
RI = 3 days
RI = 4 days
RI = 1 day
RI = 7 days
10-day Retention Interval Study
Jani? Horse
Interstudy Interval = 0, 1, 2, 4, 7, 14 days
TasksSwahili-English Vocabulary
Session 1: Study to Criterion[0,1,2,4,7, or 14 days]
Session 2: Fixed amount of further study[10 day RI]
Session 3: Test
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Inter-Study Interval (days)
Per
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Rec
all Vocabulary
FactsPictures
Facts
Objects
10-day RI
Data from 182 subjects tested for 3 sessions
6-Month Retention Interval
? Coccolith.
Interstudy Interval = 0, 1, 7, 28, 84, or 168 days
Tasks1. Learn names of little-known objects
2. Learn little-known facts
Who invented snow golf? Rudyard Kipling.
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Inter-Study Interval (days)
Per
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all Vocabulary
FactsPictures
6-month RI: Facts
Swahili10-day RI
6-month RI: Object Names
Data from 161 subjects tested for 3 sessions
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ISI/RI Ratio
Per
cent
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Rec
all
VocabularyFactsPictures
Optimum ISI = 10 – 20% of retention interval?
Let’s Plot Performance as a Function of ISI/RI Ratio
Larger Experiment now in Progress
RI = {7, 35, 70, or 350 days}
ISI = {0, 7, 14, 21, or 105 days}
X
• Web-based Learning of Facts
• Session 1: Train to Criterion
• Session 2: 2 Test/Study Repetitions
• Test: Recall, then 5-Alternative Recognition
• Large effects of spacing generalize to learning novel mathematical problem-solving skill (combinatorics) [USF]
Generalizing Beyond Fact & Vocabulary Learning
• Pattern-recognition skills may not show similar spacing effects [www.learnmelanoma.org]
Empirical Conclusions
• Using ISI of about 10-20% of retention interval seem to optimize memory over a wide time range
• Too short an ISI is much worse than too long
• Using appropriate inter-study interval can produce 100% - 200% improvement in ultimate
memory
• To determine optimum spacing, you need to know how long you want the learner to retain the information.
• For most educational goals, 6-mo. delayed reviews likely to be very cost-effective (Preuss School Study)
• Cumulative finals probably have huge effect on what students retain over years.
Tentative Practical Implications