Did you know that literate adults store between 30,000 and 70,000 words that they can read automatically, accurately, and without effort? These instantly recognized words are called sight words, and the full collection is known as the orthographic lexicon or sight word memory. This vast mental library allows skilled readers to move through text quickly and understand it with ease. It also raises an important question. How do words get stored in this way, and why do some students build their sight word memory much more slowly than others?

Sight words are words that a reader can retrieve instantly and effortlessly. They are not limited to high-frequency words like the, from, or is. They also include complex words like majestic or encyclopedia. Skilled readers recognize familiar words in less than two tenths of a second, which enables smooth, efficient reading that outpaces spoken language.

A person’s orthographic lexicon is the entire collection of words they can read automatically. This library grows as readers decode words accurately over time. For example, medical professionals may instantly recognize words like paresthesia or diaphragmatic, while people in other professions may not. That’s because doctors have decoded them successfully several times, thus anchoring them into their sight word memory. In fact, the primary goal of decoding is to build words into our sight word memory or orthographic lexicon. Repeated accurate decoding anchors words into long-term memory.

*Paresthesia is the tingling feeling you get when a limb falls asleep. Fasciculation is a tiny muscle twitch. Diaphragmatic refers to anything involving the diaphragm, such as a diaphragmatic flutter, also known as a hiccup.

High-frequency words are the words that appear most often in print. Lists such as Dolch and Fry include many of these common words. Denise Eide notes that the one hundred most frequently used words make up half of everything we read and write.

At Really Great Reading, we call these Heart Words because students must learn them by heart to read and write fluently.

High-frequency words fall into two categories.

Words that can be decoded using common phonics knowledge and letter-sound relationships (decodable words) are considered Simple Heart Words. These are words like and, it, in, and but. Notice that in each of these words, the consonant and vowel letters make the sounds that we expect.

Words that deviate from common phonics patterns or familiar letter-sound relationships (non-decodable words) are Tricky Heart Words. These are words like from, what, give, and do. Each of these words has at least one letter that spells a sound we do not typically expect it to spell. When words are irregularly spelled, research suggests that it is harder to anchor into our sight-word memory.

Many classrooms rely on rote memorization to teach Heart Words. Students see the whole word repeatedly until it sticks. While repetition may help some learners, research shows that a more powerful method exists.

Dr. David Kilpatrick explains that permanent sight word storage occurs through orthographic mapping, a process that requires three essential skills.

1. Automatic letter-sound associations
2. Highly proficient phoneme awareness
3. Word study that connects sounds to print

Word study is the superglue that anchors words into memory. When instruction skips these connections and relies only on memorization, students often struggle to remember the word over time.

This is especially important because most irregular words have only one unexpected element. For example, in the word from, the o behaves unpredictably, but the rest of the letters follow common patterns. Helping students understand both the predictable and tricky parts builds stronger memory.

Instant recognition of Heart Words, whether regularly spelled or irregularly spelled, is a common instructional focus in primary grades. Teachers use a variety of methods to help students store these words, and the most common approach is rote memorization. This often involves repeated exposure to the whole word until it sticks. Research suggests, however, that more effective methods are available.

Kilpatrick (2016) describes orthographic mapping as the process by which words become permanently stored in long-term sight word memory. When a word is sufficiently mapped, it can be retrieved effortlessly. According to Kilpatrick, effective orthographic mapping requires three skills: automatic letter-sound associations, highly proficient phoneme awareness, and word study (p. 41). Word study refers to the conscious or unconscious process of connecting the phonemes in a spoken word to the graphemes in its written form. Kilpatrick emphasizes that the word study component serves as the “superglue” that anchors words into permanent memory (p. 41).

Instruction that relies only on rote memorization often omits word study, even though most irregular words contain just one unexpected letter-sound relationship (Kilpatrick, 2015, p. 105). Understanding both the predictable and the irregular elements of a word makes it easier for students to store the word efficiently. This positions word study as a more powerful approach than flashcard-based whole-word memorization.

Rote memorization depends on students forming enough visual impressions of a word to trigger its phonological representation. This is similar to recognizing the outline of a state without understanding its features. Research indicates that storing words in long-term sight word memory is more effective when instruction includes phonics, phonemic awareness, and explicit attention to sound-symbol relationships (Kilpatrick, 2015, 2016). Incorporating word study strengthens these connections and supports more durable, transferable word learning.

To help bridge research and practice, RGR created Heart Word Magic and Heart Word Magic in Spanish. These free resources use multisensory animations and guided practice to help students connect the predictable and unpredictable parts of Tricky Heart Words.

Heart Word Magic reinforces that phonics knowledge does not disappear when a word contains an irregular feature. The alphabetic principle still applies, and students can use what they know to anchor words more effectively.

Students highlight the irregular part of the word, such as the a in what, to reinforce what they need to remember by heart.

Kilpatrick notes that most irregular words contain only one unpredictable letter-sound relationship. Understanding which parts follow common patterns helps students decode and remember the word more efficiently.

Orthographic lexicon refers to all the words a person can read instantly. Students expand this library through decoding practice, phonemic awareness, and word study connected to the alphabetic principle.