Is there one best interval between study sessions?
Vocabulary and visual-acuity practice showed different retention across spacing intervals, with the nominal 12-hour group doing well; the study does not establish a universal optimal schedule.
Source
Very Similar Spacing-Effect Patterns in Very Different Learning/Practice Domains
Study at a glance
- Design
- Human experiment — Random assignment to six spacing groups; repeated retention tests
- N
- N=107 · 120 recruited; 107 in vocabulary analysis of first two final tests; 48 with all three tests
- Population
- Healthy university-area volunteers; vocabulary sample mean age about 23 years
- Outcome
- Cued vocabulary recall and visual-acuity performance across retention tests
- Comparison
- Practice intervals of about 7 minutes, 20 minutes, 1 hour, 2.5 hours, 12 hours, or 24 hours
- Test delay
- Tests planned 1, 7 and 28 days after final learning; timing varied
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Is there one best interval between study sessions?
These passages occur verbatim in the stored paper text. They support the points listed below; they do not verify every statement in the explanation.
Who participated and how large was the analysed sample?
120 healthy participants recruited via advertisements at the local university took part.
What is the main limit on applying this result?
ANOVA II showed a smaller non-significant effect size for the between-factor SPACING (F(5,42) = 1.53, p = .2) but still a significant effect for the within-factor TEST (F(2,84) = 59.26, p = 2×10−16) and additional an interaction between SPACING and TEST (F(10,84) = 2.05, p = .038).
What they did
Researchers recruited 120 university-area volunteers and randomly assigned them to six spacing conditions ranging from about seven minutes to 24 hours. Participants practised German–Japanese word pairs and visual-acuity tasks, then returned for tests planned one, seven, and 28 days after the final practice block. The vocabulary analysis of the first two retention tests included 107 people; only 48 contributed all three tests.
What they found
Spacing affected vocabulary retention at the first two final tests. The nominal 12-hour group retained more of its learned vocabulary over the longer follow-ups than several other groups, including the 24-hour group. However, the main spacing effect was not significant in the smaller vocabulary analysis including all three tests. The actual average gap in the nominal 12-hour group was about 16 hours with substantial variation, so the label is not an exact prescription.
The limits
What it doesn't show
The four-week comparison had substantial attrition and small groups. The study varied timing for specific tasks and a particular number of practice blocks, not every possible learning schedule. Sleep and timing were not cleanly isolated as mechanisms. A peak in this experiment cannot establish that everyone should study every 12 hours, that longer spacing always helps, or that an adaptive app schedule is optimal.
Key terms
- Retention interval
- The time between the last learning opportunity and the outcome test.
- Comparison condition
- The alternative study activity or exposure against which a result is assessed.
- Generalisation
- Whether a result applies to other populations, materials, settings or outcomes.
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Common questions
What spacing interval best supports retention?
This study found a favourable nominal 12-hour condition for its tasks, but timing variability and attrition prevent a precise or universal recommendation.
Is longer spacing always better?
No. The 24-hour group did not outperform the nominal 12-hour group; the relation was not a simple monotonic increase.
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