Reading Science
Maryanne Wolf
POSSUM: What’s in a Name
Very few people actually appreciate what Reid Lyon once called “an ugly, garbage-eating marsupial.” I hope to see the day when he takes it back, particularly because I always remind him and all others, that in Latin, this word means “to enable”! It is within the latter context that I have long used the acronym POSSUM as a mnemonic to encapsulate the major contributing component parts in the first circuits of the reading brain: P (phonology, phoneme awareness, phonics, prosody), O (orthographic letter patterns), S (semantic networks), S (syntactic functions), U (understanding both the alphabetic principle and also the meanings of words within story and text), M (morphology).
It is a beautiful collection of some of the most important components in human language, oral and written. Indeed it reflects how the one (oral) is embodied in the latter (written). Further, it exemplifies the missing links in many important form of instruction and intervention in the teaching of reading. I realize that such a statement could cause a wrinkle between the eyebrows or a sensation of toes that are stepped upon. But for every person who wishes to teach as many struggling readers as possible, a cerebral or pedestrian wince or two is small cost to pay.
POSSUM represents a theoretical approach for understanding the most central cognitive, perceptual, and linguistic components in the reading brain. That said, it is Reid Lyon again who asked two decades ago (in his role as Chief Officer for work on reading and language in NICHD) whether researchers like myself, Maureen Lovett, and Robin Morris can “Put your money where your mouth is”. In other words, the charge was to ask us and other researchers to translate our best theoretical frameworks into programs that can teach real children in real classrooms. Our research group answered that charge by conducting research on what we called “multi-component” interventions. Then and now we all wanted to know whether more comprehensive emphases could be more efficacious than the more unidimensional emphases in good phonics- and phoneme- awareness based approaches. Thanks to Maureen Lovett’s extensive work on the latter, we designed a study that was able to test this question. Across three cities we compared the reading outcomes of children receiving a multi-component approach (either Lovett’s EMPOWER or Wolf’s RAVE-O) that included phonics and PA vs. children who received a double dose oof phonics/PA. The results from over a decade of research showed significant positive effects across almost every reading measure for the multi-component programs over the more traditional phonics/PA programs. There were some differential effects between the two multi-component programs that were directly related to the components in each program. The Empower program can be conceptualized as emphasizing the POM components. The RAVE-O program can be conceptualized as emphasizing the POSSUM components. It is, therefore, of no surprise that stronger effects for vocabulary and polysemy and comprehension were found for the RAVE-O program that emphasizes both the semantic and syntactic components and their incorporation in stories.
Although this research was a true breakthrough for understanding the extra benefits of a multi-component approach, the reality is that until now the primary intervention emphases were on the phonics and PA components. As important as they are, we can do better when we complement these emphases with more emphases on the oral language processes in SSUM. Indeed the relative neglect of comprehensive semantic emphases (that go well beyond what most think of as vocabulary) can lead to less developed fluency and comprehension. The most recent report by the Stanford Research Institute (2026) described a study of four excellent structured literacy programs in which phonics and PA were the major emphases with little time afforded to vocabulary development. The report underscored how the neglect of these oral language processes was related to the continued weaknesses in fluency and comprehension. Although the children made good gains for decoding at the word level, this did not generalize to their reading connected text. The authors underscored both the importance of embedding vocabulary and need for “bridging” (see Duke & Cartwright, 2021) the gap between the word level and connected text.
These findings are key to understanding how and why the structure of the new version of RAVE-O works. In RAVE-O each component in POSSUM is immediately connected to each other through the same words in both word and text level activities. For example, the first word “bat” is first taught from a semantic perspective and then from a phonological, syntactic, and morphological perspective. In this way each lesson begins by connecting the components to each other in order to increase fluency at the word level. Next every other lesson involves connecting the POSSUM components to DEEP READING processes that are emphasized in the program’s Minute Stories and chapter books. (See essay on Deep Reading in Readers’ Nest). Words never live in isolation in RAVE-O; they thrive in connection to each other and in stories.
A brief description of how POSSUM comes to life in RAVE-O involves the following principles.
No lesson in RAVE-O begins without first eliciting the multiple meanings of a group of core words that are then used in every other part of the lesson. Such a practice immediately engages the linguistic background knowledge of the children: i.e., what some of the children already know about the word and what some of the children (especially multi-lingual learners) need to know to enlarge their vocabulary. The choice of words here is highly intentional. Each word has: 1) at least two or more meanings (polysemy); 2) two or more grammatical uses; and 3) lends itself to changes by selected morphemes. The very choices of these words is meant to help children learn how the English language works and to broaden their semantic networks. Beginning with engaging them in what might be their first “courtship with words” is also a joy-filled ramp to discovering the more analytic processes that come next.
No component like phoneme awareness is taught in isolation, but always with the orthographic patterns. Like Linea Ehri we do not want phonemes to be practiced without connecting them as they are heard and spoken with the corresponding letters. In so doing we are helping children re-enact the way Helen Keller learned to put two sensory inputs together.
No words are used without developing the various syntactic uses of the word. There may be more neglect of grammar than ever before. This is particularly unfortunate because an understanding of how nouns, verbs, and other syntactic forms work contributes greatly to comprehension of ever more complex texts over time. In RAVE-O characters like Nina Noun and Victor Verb are used to bring to life how these grammatical forms can help not only their reading, but also their writing.
No words are used without showing how morphemes ( particularly the most basic morphemes ) can change the meaning of words and their grammatical use. Very importantly the ability to detect the perceptual chunks that morphemes represent can facilitate faster reading ( see essay on Fluency) .
Finally, no words are taught without their almost immediate incorporation in stories either the first or second day of their introduction. Thus a word like “track” can be read in a story in which all the meanings and grammatical uses can be found. For example, our finest Detective Dog in RAVE-O “can track the tracks by the tracks” to uncover the most recent mystery. In such a story, not only are all the component of POSSUM used, the Deep Reading process of Inference is being emphasized.
The overarching, cumulative principle of POSSUM reflects an expanded understanding of Fluency. That is, the more readers know about a word, the faster and more accurately they can read, understand, and consolidate that word in memory.
Further and equally importantly, the same principle governs POSSUM’s role in connected text comprehension. That is, the more readers know about these words, the faster and better these words will be read and understood in connected text.
From a more theoretical perspective, RAVE-O represents where our science meets story, as is elaborated in the section on deep reading and in the Albert Shanker Institute White Paper: “Elbow Room: How the Reading Brain Teaches Us to Teach”. I will hope any reader of this brief essay on POSSUM will want to take a deeper dive into the concepts discussed here by reading the “Elbow Room” paper. We need to have an expanded view of foundational skills, which is what POSSUM really is, and we need to have an expanded view of both fluency and comprehension as a set of deep reading processes. Such changes in how we think take time and effort and also patience. It has taken a long time for the Science of Reading to be accepted across many states. Yet the fact remains the very science that contributes to SOR is often narrowed to good phonics and PA, rather than the sum of many contributions like those on multi-component intervention that go well beyond unidimensional contructs. We need to have a more capacious understanding of all that has contributed to SOR, so that once more a pendulum will swing back to those who have a different unidimensional approach like whole language. The reading brain is our best model for understanding that both our teaching and our research needs to encompass the full panoply of processes that underly both oral and written language. The acronym POSSUM is at its core a mnemonic for every teacher to remember to address each of the key components of the developing reading brain in the teaching of reading. I think Reid Lyon would be pleased with where we put “our money where our mouth” has been for twenty years thanks to him.
Read next
