According to the 1995 U.S. National Assessment of Educational Progress (NAEP), satisfactory reading comprehension is usually correlated with advanced reading fluency skills. Students who spend a significant amount of time and energy trying to decipher letter sounds and word groupings are often unable to comprehend what they are reading. Conversely, students with high levels of reading fluency are more able to think about what they are reading while doing so, giving them predictably higher levels of reading comprehension. As a result, poor levels of reading comprehension are often linked to a lack of basic reading skills and can often be used to diagnose more fundamental problems like trouble with letter pairings and sounds.
The art of reading comprehension, in addition to testing basic reading skills, also depends on higher level cognitive processes and analytical skills. An effective reader is not only able to interpret the meaning of individual words and sentences, but combine them with other parts of the selection to shape a general meaning for the piece as a whole. This process allows readers to walk away from a selection with an overall idea of its theme, as well as to understand subtlety and contradictions in the piece. Reading comprehension, therefore, requires many of the same skills involved in daily problem-solving and can be a good way of developing such skills in students who need to be able to make sense of often complex and contradictory situations.
Just as mnemonic devices aid memory by condensing related concepts into a single unifying idea, effective comprehension allows students to remember an idea of a text and use that general idea to call up details and specific elements. The process of putting together different sounds and words in order to create meaning depends largely on a student's working memory, the mental space where seemingly unrelated ideas are put together to create a single unified impression or idea. Reading comprehension activities can exercise these short-term memory elements in the brain, as well as teaching students how to put together related elements to facilitate long-term memorization.
If the fundamental purpose of writing and reading in a social context is communication, reading comprehension allows students to participate in these social exchanges. Comprehension not only allows readers to take meaning away from the texts they encounter, but better allows them to understand the ways in which meaning can be coded in text and compose their own meaningful texts. In short, comprehension allows readers to be effective communicators. Deficiencies in reading comprehension, on the other hand, like general literacy deficiencies, effectively remove a child from the social context in which so many important decisions that shape his life are made.