Background knowledge and reading comprehension: why knowing matters
In short
Background knowledge is what a reader already knows about a topic, and it strongly shapes how much they understand. Students who know a topic well can understand texts above their usual level. Build knowledge with topic-focused reading, read-alouds and discussion over weeks, not one-off lessons.
What is background knowledge?
Background knowledge is everything a reader brings to a text before reading it: facts, experiences, vocabulary and a sense of how the world works. When a text mentions a hurricane, a reader with background knowledge already knows about wind, rain, flooding and evacuation, so they understand the text more fully and remember more of it.
Writers rely on that knowledge constantly. No text explains everything. A writer who describes a player "stealing second" assumes readers know what that means in baseball. Readers who don't have to work out the meaning, or simply miss it.
What did the baseball study find?
In 1988, Donna Recht and Lauren Leslie gave middle school students a passage describing part of a baseball game. They grouped students by reading skill and by how much they knew about baseball. Then they asked the students to retell and act out the passage.
Students who knew a lot about baseball did better, whether they were strong or weak readers. Weak readers with high baseball knowledge outperformed strong readers with low knowledge. The finding has been replicated in various forms since, and it shows how much knowledge can matter.
| Group | Reading skill | Baseball knowledge | Comprehension of the passage |
|---|---|---|---|
| A | Strong | High | Best |
| B | Weak | High | Strong |
| C | Strong | Low | Weaker |
| D | Weak | Low | Weakest |
Why does knowledge help so much?
Knowledge helps in at least three ways. It fills in the gaps writers leave, so the reader can follow the text. It frees up working memory, because familiar ideas take less effort to process. And it makes new information easier to remember, because there's already a place in memory to put it.
Daniel Willingham describes knowledge as making learning easier the more of it you have. Students who know more learn more from each text, which helps them know even more. Students who know less get less from each text. Over years, that gap can become very large.
How do you build background knowledge?
Build it deliberately and over time. One short video before a reading lesson helps a little, but lasting knowledge comes from weeks of reading, talking and writing about a topic. Many schools now organize reading around topics for this reason.
- Group texts by topic, so students read several texts about one subject over two to four weeks.
- Read aloud from nonfiction regularly, choosing books above students' own reading level.
- Teach the key vocabulary of each topic, since words and knowledge grow together.
- Use pictures, maps, videos and objects to make new ideas concrete.
- Have students talk and write about what they've learned, which helps it stick.
- Link reading to science and social studies, rather than treating reading as a separate subject.
Should teachers activate prior knowledge before reading?
Briefly, yes. Asking students what they know about a topic before reading helps them connect the text to what's in their heads. But keep it short and focused. A long discussion before reading can drift away from the text and leave students with wrong ideas.
Activating knowledge only helps if students have knowledge to activate. If they don't know much about the topic, it's better to give them a little key information first, such as a short explanation, a picture, or a few important words.
- Teacher
- Today's article is about bees. What do you already know about how bees make honey?
- Student
- They get stuff from flowers.
- Teacher
- Yes, nectar. They carry it back to the hive. Look at this picture of a honeycomb. As we read, look for what bees do with the nectar in the hive.
Do knowledge gaps affect some students more?
Yes. Students who grow up with fewer books, trips and conversations about the wider world often arrive at school with less background knowledge. That isn't about ability. It's about opportunity, and school can help close it.
A knowledge-rich curriculum is one of the fairest things a school can offer. When every student studies the same topics in depth, students who started with less get the same chance to build knowledge as their classmates.
How do you check background knowledge?
Before a new topic, ask students to write or say three things they know about it. A quick word sort, where students group topic words they recognize, also shows what they bring. These checks help you decide how much to front-load before reading.
After the unit, ask the same question again. The difference between the two answers shows how much knowledge students built, which is useful for you and motivating for them.
What does a knowledge-building unit look like?
Here is a simple outline for a three-week unit on weather in second grade. In week one, the class reads aloud two nonfiction books about clouds and rain, learns six key words, and keeps a daily weather chart. In week two, students read short articles on their own and in pairs, and the teacher reads a story set during a storm.
In week three, students write a short report about one kind of weather, using the words they've learned. By the end, a text about hurricanes that would have been hard in week one is much easier, because students now have the knowledge and vocabulary it assumes.