Contextual interference

When learning a movement, you often hear, "Repeat one movement enough times before moving on to the next." Research on contextual interference asks a question about this: what happens if you mix up the order?

The concept of contextual interference was first introduced in verbal learning research by the American psychologist William Battig. In motor learning, a 1979 experiment by Shea and Morgan is considered a classic study demonstrating this effect. Participants learned to move their arms to knock down obstacles in sequence. Those who practiced in a mixed order were less proficient during practice, but actually performed better when tested again after some time had passed.

Levels of contextual interference can be divided as follows.

• Low contextual interference (blocked practice) — You repeat the same task in blocks, as in AAAA BBBB. Performance becomes progressively smoother during practice, making it feel as though you are doing well.
• High contextual interference (random practice) — You mix several tasks together, as in ABCACB. Because the movement changes each time, performance during practice feels inconsistent and difficult.

You can find a detailed comparison of the two approaches in Blocked and random practice.

There are two main explanations. One is the elaboration hypothesis. It proposes that alternating between movements prompts you to compare them, making the distinctive features of each movement more clearly remembered. The other is the reconstruction hypothesis. From this perspective, each change of task requires the brain to clear the previous motor plan and retrieve a new one, and this effort leaves a stronger memory trace.

It is often presented as a prime example of Desirable difficulties, because harder practice can lead to longer-lasting memories. A 2024 meta-analysis also reported a moderate-sized benefit of high contextual interference for motor memory retention.

• Ball sports — Instead of taking repeated shots from the same spot, you vary the position and distance. Alternating between different types of serves in tennis or badminton follows the same approach.
• Strength training and rehabilitation exercise — Instead of doing all your squat sets together, alternating between squats, lunges, and hip bridges makes you prepare each movement anew.
• Playing an instrument, typing, and more — Rotating through several short passages instead of repeating a single piece follows the same principle.

• It is okay to feel less proficient during practice. Mixing up practice can make your accuracy seem worse. Learning shows up not in how smooth practice feels, but in how you perform when you try again a few days later.
• Try starting with blocked practice for a new movement. If you are a beginner or the movement is very complex, first repeat one movement to learn the basics. Then, as you become familiar with it, gradually increase contextual interference by mixing up the order.
• Start with two or three movements. Mixing too many movements at once increases the burden. Try adding one at a time as you become more familiar with them.
• Combine it with rest intervals. Combining this approach with spacing between practice periods, as described in Distributed and massed practice, can help enhance its effects.
• Try changing the conditions, too. Variable practice, in which you vary conditions such as distance, speed, or direction rather than changing the movement itself, has a similar purpose.