Why Is It Important?
Identifying main ideas and working out the relationship between main ideas and supporting details is really the essence of reading comprehension. If we cannot understand what an author is trying to say or why an author has chosen to provide us with certain details, then we are not understanding the text.
Identifying the main idea and determining what is important are prerequisite skills in summarizing a text. Summarizing requires readers to determine important—and discard unimportant—details and to put the main ideas in their own words. Summarizing has been shown to be an important strategy in helping readers improve their abilities to construct meaning. (Rinehart, Stahl, & Erickson, 1986)
Identifying the main idea teaches students to discriminate the important information from the less important details in a text. The ability to identify essential ideas and salient information is a prerequisite to developing insight. (Harvey, 2000)
How Can You Make It Happen?
The process of working out the relationship between main ideas and supporting details is not something you can teach students one morning and then move on. Rather, the pursuit of meaning should be a daily focus, something you talk about every day and build into every text-based lesson from the time that students can begin to understand what a "main idea" is (some time in first grade) through high school and beyond. In other words, while you can and ought to explicitly teach strategies for finding the main ideas in texts (e.g., look for ideas that are repeated frequently), conversations about the meaning of texts, and the more difficult question of purpose, should be part of the ongoing thoughtful classroom discourse that characterizes high-quality instruction.
When beginning instruction in finding the main idea, it is important to establish a common language and a common set of expectations. Students should understand and be able to use terms such as main idea, topic, topic sentence, supporting detail, and author's purpose.
Second, it is important to model the process of determining importance and choosing the main idea of a text. Use the think-aloud strategy to model how you determine the main idea and which details in the text support your conclusion. Students should understand that the search for meaning in texts is often hard work, requiring considerable mental effort. Provide students with tools, such as graphic organizers, for analyzing texts and documenting their analysis.
Third, there is sometimes more than one correct answer. One student's idea of an author's main idea may be legitimately different from—and equally acceptable as—another's.
Finally, and most important, establish the expectation that students will provide "text-based arguments" for their expressed beliefs about the text. If a student wants to claim that Huck Finn is an unfortunate victim, then expect him or her to point to those parts of the text that support this claim.
Here's an example of how to organize a discussion of main ideas and supporting details. First, copy a paragraph such as the following on the board or some other place where every student can read it.
Of all the inventions that had an impact on the Chinese culture during Medieval times, the most important was printing. Before there was printing, all books were copied by hand. Books were therefore rare and expensive. The Chinese began printing in the A.D. 500s. They carved characters from an entire page on blocks of wood. They then brushed ink over a wooden page and then laid a piece of paper over the block to make a print. In 1045, a Chinese printer invented printing using moveable type; the books that were made using this process helped spread knowledge throughout China, to a degree that had not been possible before.
Ask students to identify the topic or subject of the paragraph. (A good answer might be "Printing" or "The Chinese invention of printing.") If students are having trouble, you can think aloud and help them by saying that most of these sentences relate to printing, either how it was done or what it helped to do.
Next, ask students to locate the topic sentence and identify the main idea of the paragraph. (The first sentence is a good example of a topic sentence. The main idea of the paragraph is probably that printing was the most important invention because it allowed for the spread of knowledge throughout China.)
Next, ask students to identify the supporting details. Remind them that in some paragraphs, there may be sentences that are not really related to the main idea and that some details are more important than others. Point out that information about how the printing was actually done seems less important than the fact that books were previously made by hand and were therefore rare and expensive. The actual date that moveable type was invented is less important than the (implied) fact that this, in some way, made it even easier to mass-produce books. Consider asking students why this might be the case.
As a way of getting further into the idea that some details are more important than others, have students make lists of the sentences in a paragraph in descending order of importance. Then, ask them to discuss their lists in pairs or groups.
How Can You Stretch Students' Thinking?
A word web, or spider map, is a useful way of analyzing meaning. For example, a word web of the key ideas in the previous paragraph might look something like this:
It is a useful exercise to have students make their own graphic organizers such as this and then compare and discuss them. Students can make maps of randomly selected paragraphs and have others try to re-create the original, or, given word webs, students can write paragraphs that fit the webs. They can then compare their new paragraphs with the original.
Maps such as this one also provide a good foundation for other kinds of conversation. For example, what was the impact on Chinese culture? In what specific ways did Chinese culture change after the invention of printing? In addition, questions such as this provide a purpose for further reading.
