The Science of Spaced Repetition: How Often Should Students Retake Quizzes?

What Is Spaced Repetition and Why Does It Work?

Spaced repetition is the practice of reviewing information at increasing intervals over time. Rather than studying something once intensively, learners encounter the same material multiple times with growing gaps between each review.

The science is clear: spacing out learning sessions produces dramatically better long-term retention than massed practice (cramming). Research by cognitive psychologists like Henry Roediger and Robert Bjork has consistently shown that:

• Information reviewed after a delay is remembered longer than information reviewed immediately
• Each successful retrieval strengthens memory more than passive re-reading
• Optimal spacing intervals gradually increase as memory strengthens

The mechanism involves what scientists call "desirable difficulty." When we force our brains to work harder to recall information (because some time has passed), we create stronger, more durable memories. Easy, immediate recall actually produces weaker learning.

The Forgetting Curve and Optimal Timing

Hermann Ebbinghaus first documented the forgetting curve in 1885, showing that we lose roughly 50-80% of new information within days if we don't review it. But each time we successfully recall information just as we're about to forget it, we dramatically slow down the forgetting process.

The optimal timing for review sessions follows a pattern:

• First review: 1 day after initial learning
• Second review: 3-7 days after first review
• Third review: 2-4 weeks after second review
• Fourth review: 1-3 months after third review
• Subsequent reviews: Gradually increasing intervals (3 months, 6 months, etc.)

This timing creates the "sweet spot" where information is challenging to recall but still retrievable, producing the strongest learning effect.

Using Unlimited Attempts Strategically

Our quiz platform offers unlimited attempts to give you a powerful tool for implementing spaced repetition. However, unlimited doesn't mean aimless. Here's how to guide students toward effective use:

For Self-Paced Practice (Recommended Approach)

Day 1 - Initial Attempt: Students take the quiz immediately after the lecture or reading. This serves as active recall practice and identifies knowledge gaps.

Day 2 - First Review: Encourage students to retake the quiz the next day. They'll have forgotten some details, making retrieval more effortful and beneficial.

Day 5-7 - Second Review: Schedule or recommend a third attempt one week later. By now, some information will feel forgotten, which is exactly the point.

Week 3-4 - Long-Term Review: A final attempt before the exam cements knowledge in long-term memory.

Creating a Spaced Repetition Schedule

Communicate clear expectations to students:

You can even build this into your grading:

• Completion bonus: Students who attempt the quiz on at least 3 separate days (minimum 24 hours apart) receive full credit
• Grade calculation: Average of their best 3 attempts, incentivizing multiple tries

The Power of Failed Retrieval

Counter-intuitively, getting questions wrong (and then learning the correct answer) can produce better learning than getting them right. Psychologists call this the "testing effect." When students struggle to recall an answer, fail, and then see the correct response, they create a powerful memory trace.

Unlimited attempts allow students to fail safely and productively. The key is ensuring they space these attempts over time rather than taking the quiz 5 times in a row.

Setting Time Limits Based on Learning Objectives

Time limits serve different purposes depending on whether you're facilitating learning or assessing knowledge.

No Time Limit - Best for Learning

When to Use:

• Practice quizzes focused on knowledge acquisition
• Self-paced study materials
• When you want students to look up answers and learn
• Accommodating diverse learning needs
• Reducing test anxiety

Why It Works: Students can engage deeply with each question, reflect on their reasoning, and even research answers. This turns quizzes into active learning experiences rather than high-pressure tests.

With Time Limits - Adding Accountability

When to Use:

• Encouraging students to prepare before attempting the quiz
• Simulating exam conditions during practice
• Testing automatic recall and fluency with material
• Preventing extended research or collaboration
• Creating appropriate challenge for well-prepared students

Considerations: When setting time limits, consider the total number of questions and their complexity. A reasonable guideline is to allow enough time for well-prepared students to complete the quiz without rushing, while still maintaining focus and preventing prolonged answer searching.

Progressive Time Limits

A sophisticated approach uses different time limits for different attempts:

• Attempt 1: Unlimited (learning mode)
• Attempt 2: Generous time limit (practice mode)
• Attempt 3: Standard time limit (performance mode)

This scaffolds students from exploratory learning to confident performance.

When to Allow vs. Restrict Multiple Attempts

Not all quizzes should offer unlimited retakes. Your decision should align with your pedagogical purpose.

Allow Unlimited Attempts When:

Prioritizing Learning Over Assessment: If your primary goal is knowledge acquisition, unlimited attempts transform quizzes into study tools. Students can iterate, fail safely, and build competence.

Encouraging Spaced Repetition: When you want students to revisit material over time, unlimited attempts across multiple days are essential.

Reducing Stakes and Anxiety: For students with test anxiety or learning differences, the psychological safety of multiple attempts can improve both learning and performance.

Building Confidence with Difficult Material: Complex topics benefit from repeated exposure. Students need chances to struggle, receive feedback, and try again.

Creating Self-Assessment Tools: When quizzes serve primarily as self-check mechanisms, restrictions serve no purpose.

Restrict to 1-2 Attempts When:

Measuring True Proficiency: If you need to assess what students have genuinely learned (not what they can eventually figure out), limit attempts.

Maintaining Assessment Integrity: For quizzes that contribute significantly to course grades, limited attempts prevent gaming the system.

Simulating Real-World Constraints: In fields where professionals must make correct decisions under pressure (nursing, engineering), single-attempt quizzes build essential skills.

Preventing Answer Sharing: With multiple sections or asynchronous classes, limited attempts reduce the likelihood of students sharing answers.

Encouraging Preparation: Sometimes the deadline pressure of limited attempts motivates students to prepare more thoroughly.

The Hybrid Approach

Many educators find success with a two-tier system:

Practice Quizzes: Unlimited attempts, no time limit, minimal grade weight (completion-based)

Assessment Quizzes: 2 attempts, time limits, significant grade weight (performance-based)

This balances learning support with accountability.

Communicating Expectations to Students

Students often don't understand the science behind spaced repetition. Help them succeed by explicitly teaching the strategy:

Monitoring and Adjusting Your Approach

Use quiz analytics to refine your strategy:

Watch for These Patterns:

• Students taking quizzes 5 times in one hour (not spacing properly)
• Completion rates that drop after first attempt (need better incentives)
• No score improvement across attempts (questions may be poorly designed)
• Perfect scores on first attempt (quiz may be too easy or students are collaborating)

Adjust Accordingly:

• If students aren't spacing attempts, add grade incentives or clearer instructions
• If scores don't improve with retakes, review question clarity
• If everyone aces it immediately, increase difficulty or add time limits
• If completion rates are low, reduce question count or extend deadlines