Nonexamples & Contrasting Cases

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Why it works

Students learn concepts not only from examples but from nonexamples (cases that are NOT instances of the concept) and contrasting cases (comparing similar things that differ in key ways), which sharpen the concept's boundaries, what counts and what does not, and prevent overgeneralization or fuzzy understanding. Examples alone can leave students unsure where a concept ends; carefully chosen nonexamples (especially near-misses) and contrasting cases force students to attend to the defining features and distinctions. Research supports comparing and contrasting cases for building deep, precise, transferable conceptual understanding. The key is choosing nonexamples and contrasts that highlight exactly the features that matter.

The research: Research on nonexamples and contrasting cases.

The run-of-show

Choose your slot. The agenda, timings, and length update to match.

The core activity: sharpen a concept with nonexamples and contrasts

Teachers leave with nonexamples and contrasts that sharpen a concept.

Pick a concept students grasp fuzzily or overgeneralize.
Add well-chosen nonexamples (especially near-misses, what it is NOT).
Add contrasting cases (similar things that differ in a key way).
Use them to make students attend to the defining features and boundaries.

What it is, and what it is notExamples alone leave concepts fuzzy. Add nonexamples and contrasting cases to sharpen the boundaries, so students attend to the defining features and understand precisely.

Facilitator notes

Add near-miss nonexamples, and add contrasting cases.
Highlight defining features and boundaries.
Prevent overgeneralization.

Examples alone leave concepts fuzzy and overgeneralizedShowing only positive examples leaves students unsure where a concept ends. Add nonexamples and contrasting cases to sharpen the boundaries.

Adapt it

Elementary: examples, nonexamples, simple contrasts.
Secondary: near-misses, contrasting cases, distinctions.
All settings: nonexamples and contrasts that highlight defining features.

Participant handout

One page for every teacher. Print it, or save it as a PDF.

K12 Academics · Professional Learning

Nonexamples & Contrasting Cases: sharpen the concept

What it is and is not: near-miss nonexamples and contrasting cases that make students attend to defining features.

The concept students grasp fuzzily:
The nonexamples I add (near-misses, what it is NOT):
The contrasting cases I add:
How they make students attend to defining features:
A concept to sharpen with contrasts:

Make it stick

Sharpen the concept:

Sharpen concepts with nonexamples and contrasts.
Highlight boundaries.
Bring a contrasting-cases lesson to the next PLC.

Common questions

Aren't examples enough to teach a concept?

Examples show what a concept is, but not where it ends. Nonexamples (what it is NOT) and contrasting cases (how it differs from near-neighbors) sharpen the boundaries and prevent fuzzy, overgeneralized understanding.

What is a contrasting case?

Comparing similar things that differ in a key way, which forces students to attend to the defining feature. Contrasts (and near-miss nonexamples) build precise, deep conceptual understanding.

How do I choose good nonexamples?

Choose near-misses and contrasts that highlight exactly the features that matter, where the concept ends, what distinguishes it, so students attend to the defining distinctions.