How much background knowledge is needed to understand a piece of text? New research appears to discover the tipping point
By now, you’ve probably heard of the baseball experiment. It’s several decades old but has experienced a resurgence in popularity since Natalie Wexler highlighted it in her best-selling new book, The Knowledge Gap. In the 1980s, researchers Donna Recht and Lauren Leslie asked middle school students to read a passage describing a baseball game, then reenact it with wooden figures on a miniature baseball field. They were surprised by the results: Even the best readers struggled to re-create the events described in the passage.
“Prior knowledge creates a scaffolding for information in memory,” they explained after seeing the results. “Students with high reading ability but low knowledge of baseball were no more capable of recall or summarization than were students with low reading ability and low knowledge of baseball.”
That modest experiment kicked off 30 years of research into reading comprehension, and study after study confirmed Recht and Leslie’s findings: Without background knowledge, even skilled readers labor to make sense of a topic. But those studies left a lot of questions unanswered: How much background knowledge is needed for better decoding? Is there a way to quantify and measure prior knowledge?
A 2019 study published in Psychological Science is finally shedding light on those mysteries. The researchers discovered a “knowledge threshold” when it comes to reading comprehension: If students were unfamiliar with 59 percent of the terms in a topic, their ability to understand the text was “compromised.”
In the study, 3,534 high school students were presented with a list of 44 terms and asked to identify whether each was related to the topic of ecology. Researchers then analyzed the student responses to generate a backgroundknowledge score, which represented their familiarity with the topic.
Without any interventions, students then read about ecosystems and took a test measuring how well they understood what they had read.
Students who scored less than 59 percent on the background-knowledge test also performed relatively poorly on the subsequent test of reading comprehension. But researchers noted a steep improvement in comprehension above the 59 percent threshold—suggesting both that a lack of background knowledge can be an obstacle to reading comprehension, and that there is a baseline of knowledge that rapidly accelerates comprehension.
Why does background knowledge matter? Reading is more than just knowing the words on the page, the researchers point out. It’s also about making inferences about what’s left off the page—and the more background knowledge a reader has, the better able he or she is to make those inferences.
“Collectively, these results may help identify who is likely to have a problem comprehending information on a specific topic and, to some extent, what knowledge is likely required to comprehend information on that topic,” conclude Tenaha O’Reilly, the lead author of the study, and his colleagues.
5 Ways Teachers Can Build Background Knowledge
Spending a few minutes making sure that students meet the knowledge threshold for a topic can yield outsized results. Here’s what teachers can do:
- Mind the gap: You may be an expert in civil war history, but be mindful that your students will represent a wide range of existing background knowledge on the topic. Similarly, take note of the cultural, social, economic, and racial diversity in your classroom. You may think it’s cool to teach physics using a trebuchet, but not all students have been exposed to the same ideas that you have.
- Identify common terms in the topic. Ask yourself, “What are the main ideas in this topic? Can I connect what we’re learning to other big ideas for students?” If students are learning about earthquakes, for example, take a step back and look at what else they should know about—perhaps Pangaea, Earth’s first continent, or what tectonic plates are. Understanding these concepts can anchor more complex ideas like P and S waves. And don’t forget to go over some broadstroke ideas—such as history’s biggest
earthquakes—so that students are more familiar with the topic.
- Incorporate low-stakes quizzes. Before starting a lesson, use formative assessment strategies such as entry slips or participation cards to quickly identify gaps in knowledge.
- Build concept maps. Consider leading students in the creation of visual models that map out a topic’s big ideas—and connect related ideas that can provide greater context and address knowledge gaps. Visual models provide another way for students to process and encode information, before they dive into reading.
- Sequence and scaffold lessons. When introducing a new topic, try to connect it to previous lessons: Reactivating knowledge the students already possess will serve as a strong foundation for new lessons. Also, consider your sequencing carefully before you start the year to take maximum advantage of this effect.
Image Bui Nam Phong