While many of us are familiar with the idea of a learning curve, memory science tells us that we also have a forgetting curve. If you consider how much information we take in—on average, we are exposed to 100,000 words each day—it's crucial that our brain doesn't place all of this data into long-term storage. However, research shows that we remember information longer if we see it repeatedly and right before our brain is about to forget it.
Study Stream applies these age-old principles by monitoring your performance on each Flash Fact and using a spaced repetition algorithm that predicts when you should see that fact again. For example, let's say that you are studying genetics and a new card appears about Edwards syndrome:
- If you answer Don't Know, the system will serve that card again to you in about 2 minutes.
- If you answer Unsure, the system will wait about 5 minutes before presenting it to you again.
- If you choose Nailed It, the system will expand the interval to about 24 hours.
The system uses your first interaction with a card each day to determine the next interval, since repeated exposures during a short period of time are biased by shorter term memory.
As you continue to use Study Stream, other variables will influence the content that is recommended. For example, if you mark a card as Don't Know and then adjust your confidence level to Nailed It the next time you see it, the interval will be shorter than if you had marked the card as Nailed It the first time. Repeated strong performance results in longer intervals between content the user has mastered—helping you focus your time on studying material you know less well.
The system is also monitoring your response time and using that information to determine how well you know each fact. For example, if you see a card and immediately click Nailed It, that indicates a higher level of confidence than if you deliberate before making your choice.
It's important to note that you don't need to remove topics once you've mastered them. They will come back at longer and longer intervals, optimally right before you are about to forget them. However, if you completely forget a card—even if it was one that you rated as a Nailed It in the past—the algorithm will reset that fact so that you see it again within the next day.
If you set a high daily goal in Study Stream, you can expect to see a weighted mix of items that includes:
- Items that are due currently (within 48 hours)
- Cards in your backlog that are overdue for review
- New cards for topics you've recently selected but haven't seen or rated yet
In short, if you have more difficulty recalling information, the intervals will shorten, while repeated strong performance results in longer intervals between the content you've mastered. Spaced repetition helps improve your retention and allows you to study more efficiently.