Learning Science · Returning over time and mixing practice

Mixing examples to practise choosing and distinguishing

Use comparisons between confusable cases to practise noticing the feature that determines a decision.

Use the examples to connect this lesson with the earlier topics. No specialist equipment is needed.

After reading, you can

Identify a discriminating feature in two similar cases.
Design mixed examples that reveal relevant contrasts.

Choosing is part of knowing

A learner can define evaporation and condensation separately yet confuse them when explaining a misted window. Definitions supply the concepts; comparison helps identify which relationship applies. Discrimination means noticing relevant differences between cases or categories. Mixed examples can make that choice part of practice.

Place two cases together and align the same features. What is the starting state? What is the ending state? What changed in the conditions? Explain the decisive difference before adding more examples. Similar-looking pictures can demand different explanations, while different-looking cases can share the same process.

Between-category and within-category comparisons

Interleaving can bring examples from different categories close together, making differences noticeable. Blocking can bring members of one category together, making their commonalities easier to inspect. Research on artificial category learning found that the relative benefits depended on category structure. This limits any claim that one sequence always supports every kind of concept.

If categories are easily confused, alternate examples that highlight the distinguishing feature. If the learner has not yet noticed what varied members of one category share, a short group of those examples may be useful first. Ask for the comparison explicitly rather than assuming that proximity alone guarantees attention to the right property.

Authored teaching comparison: contrasting states to choose a process
Case	Starting state	Ending state	Process
Drying dish	Liquid water	Water vapour	Evaporation
Droplets on cold surface	Water vapour	Liquid water	Condensation

Use new cases to check the contrast

After comparison, remove category headings and ask the learner to classify a new case with a reason. Include a near miss and a changed surface. If a learner chooses by a superficial cue, select the next example to challenge that cue while preserving the underlying relationship.

Give corrective information about the feature, not merely the category name. A labelled answer can be memorised for one picture. Explaining what makes the picture fit prepares the learner to interpret the next one. Later checks should include unstudied examples because classification of familiar examples may reflect memory for labels rather than a usable distinction.

Worked example

Two wet surfaces

How can two wet-surface cases involve opposite state changes?

Case A shows water disappearing from an uncovered dish over time. Case B shows droplets forming on the outside of a cold container. A learner calls both evaporation because water is involved. A comparison identifies opposite changes: liquid to gas in A, and gas to liquid in B.
The tutor then uses a mirror that fogs after a warm shower and a drying puddle. The learner names the process and explains the state change in each. The cases are invented teaching contrasts. Their purpose is to practise the relationship that separates the concepts, rather than associating one word with one object.

The dish changes liquid to vapour; droplets on the cold exterior change vapour to liquid. Classify by the state change, with appropriate conditions.

Try it yourself

Think through each question before opening the answer.

What should a comparison align?
Show the answer and reasoning
Align the same relevant features across cases, such as starting state, ending state and conditions.
Unaligned descriptions can hide the decisive difference.
Why might a short blocked group be useful?
Show the answer and reasoning
It can help learners notice commonalities among varied members of one category before requiring between-category discrimination.
Common features within one category can be inspected before deciding between categories.
What does a new, unlabelled case add?
Show the answer and reasoning
It checks whether the distinction guides classification beyond memorised examples or visible category headings.
Removing the category heading prevents it from supplying the classification being assessed.

What to carry forward

Make the discriminating feature explicit.
Choose sequences according to the comparison the learner needs.

References

Sources supporting the explanations and learning checks in this lesson.