To read fluently, the brain pulls from a large sight word vocabulary that we’ve built over time. Sight words make the reading process easy, automatic, and meaningful as we string together words we’re already familiar with. But how are sight words remembered? Furthermore, how does the brain store, process, and retrieve so many words from memory as we read? 

The fascinating answer has much to do with phonological memory. There have been many discoveries that prove how sight words are stored and what this reveals about reading development. In this article, we look at some of the most interesting findings that prove how our word-reading memory functions—and why it’s not based on visual memorization. 

How is Reading Fluency Developed?

Dr. David Kilpatrick, a renowned researcher in the science of reading, provides compelling evidence that sight words are not memorized as whole visual units as previously thought among educators. Instead, words are stored in our phonological memory, the part of the brain that processes speech sounds.

In his book Equipped for Reading Success, Dr. Kilpatrick explains the process of how words are remembered. In short, for children to become strong readers, they must develop three things.

1. Alphabetic Principle — The understanding that alphabetical letters (and letter combinations) represent individual sounds in spoken language.
2. Phonic Decoding Skills — The ability to apply knowledge of letter-sound relationships and effectively sound out (decode) unfamiliar words, letter by letter.
3. Orthographic Mapping — The process of repeatedly connecting spoken words to the spelling of their written words, resulting in permanent word memory over time. Orthographic mapping relies on two things:
   1. Letter-Sound Proficiency 
   2. Phonemic Proficiency 

As Dr. Kilpatrick explains, “Oral words are made up of sequences of oral sounds. Written words are strings of letters designed to represent those sounds. A word’s pronunciation (phonology) and meaning (semantics) are connected in memory with the word’s spelling (orthography), so when the printed word is seen, the pronunciation and meaning are instantly accessed. There is no guessing or sounding out the word. The word just effortlessly pops into your mind.” (Equipped for Reading Success, p. 38-39).

What is Phonological Memory? 

Phonological memory refers to the part of our brain’s memory system that stores and retrieves speech sounds. 

It plays an important role in reading development because to read words, a reader must know how to match visual letters with the sounds they represent. Then, they must decode multiple speech sounds—each pulled from phonological memory—and blend them together to reveal the whole word. Their knowledge of the whole word is also stored in phonological memory. 

The letter sounds, pronunciation, syntax, and meaning of words all come from this phonological memory system, enabling beginner readers to sound out and comprehend words in print. Then, through orthographic mapping, this memory system stores the now-familiar words. Readers can easily recognize mapped words which then builds reading fluency. This is the “phonological filing system” as Dr. Kilpatrick calls it.

Proof That Words Are Remembered in Phonological Memory

In research on reading development, there’s plenty of evidence that word recognition is not based on visual memory alone. Rather, words are stored in phonological memory—the part of memory that relates to verbal language. In his book, Equipped for Reading Success, Kilpatrick illustrates examples of this evidence. Here is a summary of the key findings. 

1. We Can Read Different Fonts and Typestyles

As literate individuals, we can read texts in various fonts and styles that we’ve never encountered before. This is one of the simplest facts that demonstrate word-reading memorization is not visual.

For example, we can read:

• Mixed-case words (sPeLLiNg ThAt’s LiKe tHiS)
• Different fonts (serif, sans-serif, bold, skinny, bubbly, squiggly, etc.)
• Capital letters (ALL CAPS LIKE THIS) and lowercase letters (all lowercase like this) in various contexts 
• Different handwritings—from a doctor’s sloppy scribbles to a stranger’s unique print
• Cursive and formal scripts

There’s no possible way a reader has been previously exposed to every style of text they will ever read. If words within an unfamiliar or hard-to-read piece of print have not been saved to visual memory, how can the reader decode them with ease? We know that most words are not stored in memory as whole visual units. No matter what font we read, our brains pull from phonological memory to decode new (and even barely legible) print styles. 

2. We Know That Visual Memory Differs from Word Memory

The field of cognitive science has discovered that visual memory and word memory operate differently in the brain. The average literate adult can verbally identify words in print faster than they’re able to name visual objects in pictures. For example, if you compare the speed at which adults would say words for everyday objects (“house,” “phone,” “car,” etc.) based on reading the word aloud or identifying the object in a picture, the word recall speed is faster in reading. 

Children with reading disorders have shown similar scores to proficient readers on visual memory tests, despite having significantly lower scores in word memory. If reading was dependent on visual memory for word recall, why would children score the same for visual tests but fail word-reading tests? This rules out a visual-based word memory. 

Even more surprising is the finding that deaf individuals—despite achieving normal visual memory scores and having no visual impairments—typically struggle to obtain expected reading proficiency for their age. It’s estimated that one in three deaf students graduates high school with a reading level at or below third grade (Center on Literacy and Deafness). This hints at the importance of verbal (phonological) language in the development of word-reading memory.

3. We Correlate Sight Words With Phonemic Awareness

Sight words include any word that a reader is familiar with and can recognize by sight, with no need for decoding. There is a lot of correlation shown between phonemic awareness and sight words, whereas there is very little correlation between visual memory and sight words. 

4. We Forget Words in Working Memory, Not Phonological Memory 

Think about a time when you were trying to explain something in a conversation but you forgot the specific word to describe something. You know the meaning of the word and the point you’re trying to make, and yet you can’t remember the actual word for what you’re saying. You might stammer, “What’s the word…? It’s on the tip of my tongue!” but your mind goes blank. 

This brief memory lapse does not happen when reading text that contains words we already know. For example, say you’re trying to remember the word “simmer” when verbally explaining the process of cooking something on the stovetop. You can’t remember the word that means not quite a boil but maintains cooking at a high temperature. Alternatively, if you were to read a recipe that stated, “Simmer on low for 20 minutes,” you’d have no problem recalling the word or what it means. 

Why would we forget words in working memory but not in phonological memory? Word recall is not set in working memory. It has to do with phonology and the process of orthographic mapping. 

5. We Have a Limited Capacity for Visual Memory 

Although it’s been previously assumed that whole-word memorization is a required process for reading, our brains cannot store so many visualizations—at least not accurately. Research on visual memory has found that human memory is incapable of storing more than 30,000 to 60,000 words for retrieval. 

When trying to remember a new address or phone number, what do you do? Most likely, you read the numbers and then repeat the string of digits either out loud or silently in your head. Quick, grab a piece of paper or your cell phone—write it down before you forget! If we could imprint text onto visual memory, this process would be much easier. We wouldn’t need to repeat the digits until we could offload them from our working memory. 

Consider the fact that all of the above examples reveal that we use “visual input” to process text initially. However, we do not use visual storage to “memorize” the visuals we see. Instead, we rely on our knowledge of phonemic awareness, phonological memory, and sight words. 

Understanding Phonological Memory: Help Children Learn to Read

Why does all of this matter? Knowing the role and function of phonological memory in reading development is crucial for effective literacy instruction. By understanding how words are decoded, remembered, processed, and retrieved, you can prioritize the necessary and effective phonics strategies when helping children learn to read. It’s highly advised you avoid whole-word memorization strategies–such as memorizing large lists of high-frequency words or “analyzing” the outer shape of a word–because these are common practices that are ineffective.

Learn more about evidence-based phonics instruction at Phonics.org where we explain reading science with practical applications for families and teachers.