According to Ph.D. in cognitive science Art Kohn, humans forget 50% of the data they see or hear within an hour. Moreover, people can't recall 70% of it after one day nor 90% after one week.
Therefore, a reader of short books—below 250 pages or revolving around one idea—forgets 90% of a book's information after two weeks of starting assuming an average reading speed. Shocking, I know, but it reveals why people mumble when sharing anything but a book's core idea.
People also forget the information from long books—longer than 250 pages or shorter than 250 but with scattered ideas backed by science.
However, unlike short books, the length and complexity of long books allow the brain to recall information more effortlessly in the long term.
Longer books give you more information to encode
Encoding is a process where the brain creates a mental representation of what you see or experience.
These mental representations are called traces, and your short-term memory stores them.
The traces from your short-term memory don't have meaning during the encoding process. Instead, they are like most book notes: quickly written but easily forgotten. Therefore, it's crucial to move the traces from your short to your long-term memory.
You can help your brain move information to your long-term memory by using the knowledge you read in real life. And because long books have more information than short ones, you'll have more data to apply in real life during the next stage: consolidation.
Longer books give you time to consolidate the information
Consolidation is a process where the brain structures the traces it made during the encoding stage.
"Scientists," say the authors from Make It Stick, "believe that the brain replays or rehearses [during consolidation] the learning, giving it meaning, filling in blank spots, and making connections to past experiences and to other knowledge already stored in long-term memory."
While long books challenge your brain to store more information than short ones, the length gives your brain more chapters, concepts, and frameworks to encode and eventually consolidate.
For example, people who read a dozen 1000-page medicine books have more medicine-related information stored in their short-term memory than people who read a dozen 100-page books.
So, when the former's brain is trying to consolidate the 13th book's data, it'll have 12000-pages worth of medicine data to associate with previous knowledge, instead of 1200.
You can use several methods to force your brain to connect old and new knowledge.
I also build hypotheses based on the frameworks and principles I read and rant about them with friends in real life—which is harder to do than writing because, you know, you need friends.
Longer books challenge your information retrieval capabilities
Retrieval refers to the process where you remember or try to remember the information from your brain's long-term memory.
When you retrieve data, the brain strengthens the memory traces, reducing your chances of forgetting the information you saw or experienced.
At this stage is where short books seem to be better than long ones. It's easier to forget a concept from a 1000 book than a 100 page one in the short term. But retrieving information isn't the goal per se, as it doesn't guarantee you'll recall it in the future.
Instead, the goal is to struggle to retrieve data—which longer books are better at causing.
"The greater the effort to retrieve learning, provided that you succeed," say the authors of Make It Stick, "the more that learning is strengthened by retrieval."
Therefore, the challenging aspect of recalling more information from a long book than from a short one is not a downside but a necessity.
Reflect on the book-length you tend to remember easier
My life, potentially as a coincidence, backs this article's hypothesis.
For example, people never seem to name one idea from Austin Kleon's Steal Like an Artist other than the suggestion to steal from many sources and then create your style. But when I encounter a reader of long books like those reading Nassim Taleb's Incerto, they can't stop connecting ideas from the book with everyday life.
Moreover, my brain tends to consolidate more data from long books than short ones before deliberately connecting them with previous ideas.
The hypothesis that long books are better from a learning perspective than short ones aligns with today's understanding of the human brain and my experience. But it might not apply to you.
So, if you have 10 seconds, send me a Twitter DM saying how true or false the following statement is for you, "I retain a higher percentage of information from long books than from short ones."