Learning Science · Returning over time and mixing practice
Mixed and blocked practice are different arrangements
Distinguish the order of practice categories from the timing of returns to them.
Use the examples to connect this lesson with the earlier topics. No specialist equipment is needed.
Back to the chapterAfter reading, you can
- Identify blocked and interleaved arrangements.
- Recognise how mixed practice can add method-selection demands.
Order and time are separate
Suppose A is area problems and B is perimeter problems. An A–A–A–B–B–B sequence is blocked by type. An A–B–A–B–A–B sequence interleaves the types. Either can be completed in one sitting or spread across days. Interleaving describes the arrangement of categories; spacing describes the separation between returns.
In many experiments, interleaving also spaces examples of the same type, so several features change together. That does not make the concepts identical. A clear description should state the sequence and timing. Otherwise a benefit attributed to "mixing" may partly involve delayed returns or different opportunities for comparison.
| Arrangement | Example sequence | Distinct question |
|---|---|---|
| Blocked | A A A B B B | Practise one type before another |
| Interleaved | A B A B A B | Choose among types repeatedly |
| Spaced | A today; A later | Revisit a type after a stated interval |
A heading can choose the method for you
A page headed "perimeter" makes method selection easy before the learner reads the problem. A mixed page can require deciding whether the question concerns boundary length or surface coverage. This adds a demand that belongs to competent use. Executing a method well after its name is supplied does not show that the learner can select it.
Mixed practice should still be coherent. Alternating unrelated activities merely to create frequent switching can impose costs without teaching a useful distinction. Choose types that the learner needs to identify or compare, and provide the prerequisite knowledge to attempt them. A new type may need initial explanation and a worked example before it joins the mixture.
Evaluate the intended demand
In a classroom mathematics experiment, interleaved practice improved performance on a later unannounced test relative to blocked practice for the studied material. This supports considering the selection demand, while the result remains tied to the tasks and design. It is not a rule that every minute of every subject should be mixed.
Record separate errors in choosing a method and executing it. If selection is correct but calculation fails, targeted component practice may help. If calculation is sound once prompted but method choice fails, comparisons and mixed cases may be more useful. The arrangement should follow the demonstrated need.
Worked example
Area and perimeter
Why does multiplying for an edging question reveal a selection problem?
- A learner correctly computes the area of a rectangle as length times width on a page of area questions. On a mixed page they multiply for every item, including one asking how much edging is needed. The problem is selection: edging follows the boundary, so the relevant quantity is perimeter.
- The tutor compares the same rectangle’s floor covering and edging, then mixes new rectangles with explicit reasons required. They also include a few focused calculations if arithmetic is weak. The mixed sequence practises choosing between known relationships; it does not replace teaching those relationships in the first place.
Area covers a surface; perimeter follows a boundary. Mixed cases can practise choosing the relationship after both are understood.
Try it yourself
Think through each question before opening the answer.
Can blocked practice be spaced?
Show the answer and reasoning
Yes.
A learner could practise one category on each of several separated occasions. Category order and time gaps are distinct features.
Why can a worksheet heading hide a knowledge gap?
Show the answer and reasoning
It tells the learner which method to use.
Correct execution then gives limited evidence about independent method selection.
What would make a mixed set poorly designed?
Show the answer and reasoning
It may introduce unfamiliar prerequisites or unrelated switching without a useful comparison.
The mixture should exercise a relevant choice with adequate preparation.
What to carry forward
- Describe sequence and timing separately.
- Mixed practice can teach selection among known approaches.
References
Sources supporting the explanations and learning checks in this lesson.