Scaling the “Dinosaur Effect”: Topic vs. Theme in Elementary Classrooms

June 14 2023 – Susan Pimentel, David Liben, and Meredith Liben

Most primary teachers and parents of early-grade children will recognize what we’ve dubbed the “dinosaur effect,” marveling at the capacity of young children to capitalize on their passionate interests in, say, dinosaurs—to learn and retain astounding stores of knowledge about everything dinosaurs. Not only do complicated, entirely new, multi-syllabic dinosaur names seem to stick the instant youngsters are exposed to them, but children also pick up tons of ancillary knowledge and vocabulary. Aided mightily by their background knowledge, children use their emerging decoding skills to avidly read simple texts about dinosaur diets, how dinosaurs lived, and what the earth was like way back when. 

How does this happen? It turns out research has an answer.

In this article, we want to explore how different English language arts (ELA) curricula—some organized by topics, many others organized by themes—succeed in harnessing this “dinosaur effect.” Which organizational structure best exploits the expanding body of research about domain-specific knowledge so that students can know more words and become better and more knowledgeable readers in the process? 

When students read texts on a specific topic, whether of their choosing or suggested by a curriculum, they read (or have read to them) multiple related texts in which knowledge about the topic deepens and widens over successive readings. Texts are selected because they share concepts in common. For example, if space science is the topic, students are likely to encounter words that describe concepts like “exploration,” “phenomena,” “massive,” distant,” and “habitable” in the texts they read. The previously unfamiliar quickly becomes familiar. As students develop more expertise with the topic, they can comfortably absorb the more sophisticated words that name and describe aspects of the topic. 

One common misunderstanding about topically organized units is that the vocabulary gains are largely domain-specific (what educators call “Tier 3”), but as the example above demonstrates, many of the words are those that students will encounter in all kinds of non-space science contexts. They’re the more sophisticated words that we want students to be able to understand and use. By teaching such words as part of a topical dive, we provide students with the helpful connections needed to retain them for future use—so that the words can be applied in new contexts. 

Reading several texts on a single topic is like activating Velcro in students’ brains, to which more knowledge can be added and from which references can be drawn for future use in different settings. Building such repositories of knowledge enables students to make relevant inferences while reading, accelerate their vocabulary learning, and integrate new knowledge with existing knowledge. 

Students become confident readers as they become experts on a topic—and well-designed curricula can capitalize on this benefit to make vocabulary learning an incidental byproduct, making it possible for earlier texts to “bootstrap” language and knowledge learning in later texts. A recent seminal study affirms this outcome: The single most robust method for rapidly growing students’ vocabulary (and thus knowledge) is reading conceptually related texts that cohere together to create a picture of a topic—much more than students reading unrelated texts. This is the basis of recent work by researchers showing the power of text sets built around related topics.

It’s impossible to overstate the significance of these findings. But historically, most of our ELA programs don’t organize learning in this satisfying way. Instead, they organize by thematic units. 

Do themes hold the same power? 

One could rightly argue that most texts—even those part of a theme—impart some knowledge. True enough. But they don’t add up to the giant advantages students gain in vocabulary and deepening reading from learning via a coherent body of knowledge. Take this 5-week unit organized around the theme “Getting from Here to There” from a basal series. It would be easy to guess it is about travel. It’s not. Here’s how the unit plays out:

  • Week 1 includes texts relating to “Cultural Exchange,” which might have fit. 
  • But then, Week 2 flips to texts that address “Being Resourceful.” 
  • Week 3 is all about “Patterns.”
  • Week 4 is “Teamwork.” 
  • Week 5 focuses on the magazine Time for Kids.

Forget that the “Getting from Here to There” theme feels tacked on and will be opaque to students; the real shortcoming is that students will read a hodgepodge of texts that jump from topic to topic, making the likelihood of encountering related concepts—and the vocabulary that names and supports them—slim. This places a considerable burden on direct instruction for vocabulary gains. Of course, direct instruction has a vital role in deepening vocabulary. Still, there are far too many words for students to learn the volume of vocabulary they need through only direct instruction.

There are other drawbacks to theme-based instruction. Introducing broad themes in advance of reading can prompt students to engage in overly general conversations rather than focusing on the specific activities that make them stronger readers: drawing evidence from the text, gleaning meaning from it, and amassing their knowledge about the world together in a lively exchange of ideas. Relentlessly organizing instruction around themes can have students skimming the surface of texts. Themes can overwhelm the specifics of a text and constrain students’ analyses. Even when students encounter subjects in a text that they might find interesting and want to know more about, there is often not enough reading on the subject to do more than pique their interest, leaving them hungry for more without satisfaction. 

In the last 10 years, several new knowledge-based, comprehensive ELA programs—featured on this website—have taken full advantage of the research and are providing the intellectual stimulation students crave. Teachers using these programs report their striving readers are more motivated than ever. They learn about the world along with everyone else in the class. They have access to the grade-level core text and various conceptually related texts offered at different complexity levels. That way, all students can read independently and deepen their knowledge. Students are no longer shunted into low-level reading groups to read a collection of random texts, with everyone acutely aware of the schism in quality and access. The result is that all students learn more—and learn more from one another together. 

We recently saw this learning in action. During an initial reading on dolphins (as part of a larger unit on sea mammals), a third-grade class of students learned that dolphins regularly ascend to the surface and descend shortly after. Together, the class quickly determined the meaning of “ascend” because they already had learned dolphins were mammals, did not have gills, and needed to rise to get oxygen. The same happened with the word “descend” (used in connection to dolphins feeding). For most students, the word “surface” became obvious, too, as the place where the water met the air. They learned three powerful Tier 2 words seamlessly and incidentally—and in minutes—because of the repeated content and context support—far more meaningful and lasting than word lists or traditional vocabulary exercises can offer. 

Organizing ELA coursework around topics driven by social studies and science standards and student interest allows one instructional method to do triple duty by simultaneously building knowledge, vocabulary, and literacy. First, imagine the compounding impact on students’ growth if an entire year of ELA study was dedicated to conceptually connected topical units. Now, imagine the impact on that growth if the same approach began in K and extended through students’ 12th-grade year—growth most consequential for students who come to school with smaller word stores and less general world knowledge.

So how do we best do this for our students? Through topics or themes? Does it even matter? We subscribe that it matters. A lot.