Picture a classroom of first graders. There’s a quiet hum in the air as each child leans over a book. One student sounds out the word birthday: “b… ir… th… d… ay.” She blends the sounds together, pauses, then grins as she says the word aloud: “Birthday!” No teacher is at her side prompting her. No flashcard or memorized list has fed her the answer. In that moment, something invisible and yet incredibly important just happened.
She’s just taught herself a word.
That single instance is more than a learning milestone, it’s a glimpse into a cognitive process that holds the key to becoming a skilled, lifelong reader. And it raises a question that cuts to the heart of literacy instruction:
How do we actually learn to read tens of thousands of words when our brains can only memorize a couple thousand symbols at most?
This is more than just an interesting riddle. It’s a central puzzle in reading science, and one that every educator, curriculum designer, and literacy advocate should understand.
The Limits of Human Memory, and the Scale of Reading
Let’s start with some surprising math.
Cognitive scientists estimate that human memory can manage about 2,000 distinct visual symbols. Yet the average adult knows and uses upwards of 40,000 words. Some estimates go even higher, estimating that well-educated adults may recognize over 200,000 words across reading, writing, and speaking.
That discrepancy is staggering. If we can only remember 2,000 symbols… how do we possibly learn to recognize and read tens of thousands of words?
The answer isn’t brute force memorization. It’s not flashcards or word walls or vocabulary drills alone. It’s something deeper, and far more elegant.
It’s what researchers like Dr. David Share call “the self-teaching hypothesis.”
The Secret Power of Decoding
According to the self-teaching hypothesis, once students are taught how to decode words, matching letters (graphemes) with sounds (phonemes), their brains begin to do something remarkable: they start teaching themselves new words independently.
Each successful decoding attempt creates a neural imprint of that word’s structure and meaning. After just a few exposures, the brain stores a visual memory of the word, what scientists call an orthographic representation. That means the word becomes instantly recognizable without the need to sound it out again. In essence, the student has added a new word to their mental dictionary, not by memorizing it directly, but by unlocking it through decoding.
Here’s where the process becomes transformative: this self-teaching can happen again and again, across thousands of words, with minimal direct instruction. Once the foundation is laid, the brain's reading circuit can do the heavy lifting.
It’s like building a mental GPS. The first few trips require a map and directions (decoding), but soon, the brain knows the route by heart.
A Real-World Example: Meet Jordan
Let’s look at a real classroom example.
Jordan is a second grader with a solid grounding in phonics. During independent reading time, he comes across a new word: unexpectedly. It’s long and unfamiliar. His teacher isn't right next to him, but Jordan starts working through it: u … n … ex … pect … ed … ly ….
He stumbles, but he tries again. Eventually, the word clicks, he blends it and recognizes it from context. The next time he sees the word, it feels more familiar. By the third or fourth exposure, he knows it instantly. No one explicitly taught Jordan that word. But now it’s his. He’s taught it to himself.
This is the self-teaching hypothesis in action, and it’s one of the most efficient ways the brain builds reading fluency.
The Science Behind the Scenes
This idea isn’t just theoretical, it’s grounded in neuroscience. French neuroscientist Dr. Stanislas Dehaene emphasizes that skilled reading is all about the brain’s ability to decode unfamiliar words. He explains that once the brain forms a reading circuit, a network linking visual, auditory, and meaning-processing regions, it becomes capable of mapping new words quickly and efficiently.
This process depends on neuroplasticity, the brain’s ability to adapt and strengthen new pathways with use. Once a child learns to link letters with sounds automatically, every new decoding attempt strengthens those circuits and builds vocabulary.
And here’s the amazing part: this isn’t just true for kids. It’s how adult readers continue to learn new words, too.
But Self-Teaching Doesn’t Happen by Accident
There’s a catch, and it’s important.
Self-teaching only works if certain prerequisites are met. Children must:
Without these skills, decoding stalls, and so does self-teaching. That’s why strong phonics instruction, paired with phonemic awareness, is so essential in early grades.
When we build these foundations well, we empower students to grow exponentially as readers.
What This Means for Instruction
So what does this mean for how we teach reading?
It means we don’t have to teach every word. We can’t, and we shouldn’t try. Instead, we should focus our efforts on equipping students with the tools to unlock language for themselves.
It means our instructional time is best spent building those foundational decoding skills, phonics, phonemic awareness, fluency, so that students can activate their brain’s natural ability to learn new words through experience.
It also means that curriculum choices, intervention strategies, and assessments should reflect this understanding. Are we measuring students’ ability to decode and blend? Are we giving them rich opportunities to apply those skills in real reading contexts? Are we supporting automaticity?
Because once decoding becomes automatic… learning takes off.
What’s Next? A Deeper Dive Into the Science of Reading
This is just the beginning.
In our Science of Reading Academy online course, we explore the self-teaching hypothesis in more depth, alongside other evidence-based frameworks that are transforming classrooms around the country. You’ll get practical strategies, foundational research, and real-world examples to inform your instruction and support every learner.
We’ll also share insights from a groundbreaking 2022 meta-analysis that both affirms and expands on David Share’s original self-teaching model, revealing new opportunities and challenges ahead for reading science and practice.
Whether you’re a classroom teacher, a literacy coach, or a district leader, this webinar will leave you with a richer understanding of how readers grow, and how you can help them get there.
Ready to Reimagine How Students Learn to Read?
👉 Sign up for our Science of Reading webinar series to explore the self-teaching hypothesis and more.
Together, we’ll uncover what the brain really needs to read, and how we can build classrooms where every child becomes a confident, capable reader.