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SRS – Spaced Repetition Systems: How It Works and Why It Is Effective

SRS in brief

SRS, or “Spaced Repetition Systems” is a learning technique that aims to hack the human brain’s learning curve through strategically timed material review. The learning technique focuses on steadily increasing revision intervals to transfer short-term knowledge to long-term memory with greater ease. SRS is essentially exploiting the psychological spacing effect that the brain is better at learning over time instead of in a single learning session.

SRS is particularly useful when a learner is seeking to retain large amounts of information indefinitely. This is why SRS is often used in language learning, where learners seek to retain large amounts of vocabulary for long periods of time.

How it works

SRS times reviews and repetitions strategically in order to maximize learning efficiency. This means reviewing material right before it is forgotten and steadily increasing time intervals between repetitions until you arrive at long-term intervals proving that the knowledge has been committed to long-term memory.

In other words, SRS is an optimization method that reduces the brute force behind language learning by timing repetitions and learning to coincide with short-term, mid-term, and long-term memory cycles. SRS increases learning speed and efficiency by allowing learners to not just work hard but also work “smart”.

Technology has been a great help in making SRS more accessible. Working through software and applications automates the SRS timing and alerts learners to when and what they need to study. In practice, SRS increases how manageable learning a language is by automatically spreading out the workload into digestible chunks. Furthermore, it increases the overall language learning pace due to the increased retention while also reducing the workload, which in turn helps learners maintain higher levels of motivation and feel their progression sooner in the learning cycle.

See more: Learn Chinese Characters Efficiently With The Spaced Repetition Learning System.

Here is an example of SRS in action

I learn the word “A” today at 7:00 AM. At 11:00 AM, that word is ready for me to review. I review it, thereby reinforcing what I have learned earlier right before the time I would expect to start forgetting the word “A”.

8 hours later, at 5:00 PM, the word “A” is ready for me to review again. I review it and therefore reinforce the memory further. The next review happens 12 hours later at 5:00 AM the next day.

If I happen to get the review wrong the next morning when I wake up, instead of coming at the same 12-hour interval or at a longer interval, the next review comes back to 8 hours after my mistake. Each time I make a mistake, the review interval time is reduced while each time I successfully review the word “A”, the interval is increased.

Once I review the word “A” successfully after a 12-hour review interval, the next review occurs 24 hours later. After the 24-hour interval comes to a 48-hour interval.

From this point on the interval keeps increasing. The next review occurs 1 week later, then a month later, then 3 months later, and then 6 months later.

Usually, the word will be within my working vocabulary after the 48-hour interval. From that point on, each interval makes sure I don’t forget that word even if I am not using it on a daily basis.

When you study many words at once with this method, you can really start to see the effects of SRS in action and notice an increase in vocabulary acquisition.

History & background of the Spaced Repetition Systems

SRS was first thought of in 1932. Professor C. A. Mace proposed the method in the book Psychology of Study. A few years later, H. F. Spitzer tested spaced repetition learning on sixth-grade students in 1939. The research suggested that the method was effective. However, SRS went relatively unnoticed despite its apparent success. About 20 years later in the 1960s, cognitive psychologists started experimenting with SRS timing in order to improve recall.

Over time, multiple SRS algorithms came to fruition. Examples include Neural networks based algorithms, the “Leitner System”, and “SuperMemo” type algorithms.

If you are interested in scholarly articles about SRS, head over to Google Scholar and type in SRS. Many studies have been conducted and it is a great place to find out more 🙂

This article was published by the Pandanese Team.

Pandanese is a Spaced Repetition Systems platform specifically made for Chinese Mandarin learning and much more. Visit Pandanese @

This Post Has 12 Comments

  1. CvonD

    Great article! Spaced-Repetition, well structured and practiced correctly, yields excellent results.

    One of the most powerful breakthroughs that changed completely the way I approach learning today has been to attend the online course on Coursera ( _Learning How To Learn_, by Barbara Oakley and L. Sejnowski. The two (now world-famous) scientists divided the four-week course in well-defined modules that explain everything about spaced repetition, the brain, physical fitness, mental preparation etc. I wished that course had been available when I was attending High-school!

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