How Overlearning Improves Performance

To understand how overlearning has an impact on our ability to learn a new skill, researchers exposed two groups to a series of visual perception learning exercises – basically orienting lines on a computer screen, known as Gabor patches.

In the first group, learners stopped practicing as soon as they stopped getting better – this usually happened around the eighth block of training. They then took a 30-minute break. After this break, they trained on another distinct, but similar visual learning exercise. The following day they took a post-test. In this test, subjects performed well on the second task – the one they learned most recently. They failed the first task – the results were the same as if they had never trained at all.

Takeo Watanabe, a professor of Cognitive, Linguistic, and Psychological Sciences at Brown University and an author on the study, declares that “in the usual situation in which you stop training on a new skill immediately after you’ve mastered it, the area of the brain related to the skill is still plastic.”

Brains are very flexible – they are great at learning new skills. What Watanabe’s research suggests is that if you stop training a skill after you have just acquired it, the brain stays in its ready-to-learn state. If you then start learning a second similar task while your brain is in this plastic state, it will overwrite the first skill. It will seem like you have never studies the first skill at all. This is known as “retrograde interference.”

In the same study, a second group of subjects “overlearned.” This group continued practicing past the point of competency, for eight more blocks, or sixteen blocks in total. Like the first group, after a 30-minute break, they trained on a second task, and the next day they took a post-test.

Those who overlearned performed a lot better on the first trained task than those who did not overlearn. It just so happens that spending 20 extra minutes practicing a task you’ve already perfected leads to everlasting improvements. The benefit is that the second learning doesn’t interfere with the first one. However, this does come with a cost. 

Robert Goldstone, a distinguished professor for psychological and brain sciences at Indiana University declares that “the other part of the story, is that you learn the second task less well.”

The first group, the ones that didn’t overlearn, performed better on the second task. However, the sum of their improvements on both tasks was below that of the overlearning group. In other words, the overlearning group learned the first task a lot better, and learned the second about half as well as the first group. The first group, however, though they trained on both tasks, basically only learned the second task.

To understand why this is the case, Watanabe and his colleagues turn to Magnetic Resonance Spectroscopy (MRS). When it comes to brain scans, MRI or fMRI machines are more well known, but fMRI machines measure brain function by tracking oxygen in the brain. Areas of the brain that are working hard use up more oxygen, so it’s possible to link brain function to oxygen usage. MRS machines, on the other hand, track chemicals like carbon and nitrogen that are present in the brain’s neurotransmitters. They allow scientists to asses which neurotransmitters are present in the brain.

Using the MRS machine, researchers repeated the aforementioned experiments, but with two changes. First, the two groups trained on either the usual (eight-block) condition, or the overlearning (sixteen-block) condition, but without a second training. And, before the first test and training, researchers scanned the subjects’ brains using the MRS machine. Researchers also scanned their brains 30 minutes after the training, and once more 3.5 hours after the training. The post-test was still on the second day.

What Watanabe found was that if you don’t overlearn, the brain has higher amounts of glutamate-dominate excitatory. Glutamate is a chemical that makes your brain plastic or more adept at learning. However, overlearning decreases the amount of glutamate, and increase the amount of GABA, a chemical which stabilizes the brain. “If you overlearn the skill, your brain state changes very rapidly from being plastic to being stable,” says Watanabe. This in turn means that your brain has more time to lock in the skill, preventing it from being deleted. 

If you’re a teacher and you want to make certain that your students build a good foundation for a specific topic before moving on to something more complex, it makes sense to overlearn the first topic before tackling the second with the aim of returning to the first topic at a later date.