Principle
Block briefly when the pattern is still forming
Contrast helps after there is something stable enough to contrast.
When it fits
- When early interleaving creates confusion before the learner can recognize either pattern on its own.
When to avoid it
- Blocking can also create false fluency if it continues too long. Retest with mixed cases once the basic structure is available.
Why it matters
Use a short blocked introduction when the learner cannot yet identify the basic structure of each option. Once the patterns are recognizable, introduce mixed cases that require selection. The transition point comes from performance, not a fixed number of repetitions.
An example
A learner first practises two German sentence patterns separately, then mixes them once each can be produced and the remaining challenge is choosing the right one.
Check your result
The learner moves from acquisition to discrimination because the observed error changed.
Keep this limit in mind
- Blocking can also create false fluency if it continues too long. Retest with mixed cases once the basic structure is available.
Connected ideas
Use beforeUse near-neighbour cases to train discrimination
Evidence and sources
A meta-analysis of interleaving found a moderate overall benefit (g = 0.42) but strong moderation by material type and category similarity, including conditions where blocking performed better.
Interleaving should be selected for a discrimination problem rather than used as a universal mixing rule.
Similarity matters: A meta-analysis of interleaved learning and its moderators · Abstract