Unlike listening comprehension, reading comprehension is not something for which our brains have evolved. Whereas oral comprehension seems to develop “naturally” with minimal deliberate intervention, reading comprehension is more challenging and requires deliberate instruction.

Humans have been accomplished in oral comprehension for 100,000 years or more, and virtually all humans do it; reading comprehension has only been practiced for 5,000 years, and for most of that time the majority of humans did not do it. It should not be surprising that reading comprehension is difficult. The application of comprehension to text amplifies our mental capacities. It is fundamental to full participation in society, now and for the foreseeable future.
Levels of processing in reading

It is important to understand that reading occurs at several different levels, and how these levels interact. One way of describing those levels is presented in Figure 1 (see below). The lowest level shown there, Words, sits on top of many even lower levels of processing. Successful word recognition (either pronunciation, or, more rarely, recognition of meaning without being able to pronounce) is a prerequisite for the higher levels of comprehension. If some words cannot be recognized, the higher levels can compensate to some extent (shown as “top-down processing” in Figure 1). Unknown words can be inferred in some cases; however, this is more difficult than it sounds, it can only work for some kinds of words and only for a small number of words in any text, and it is very processing intensive. Once words have been recognized, the question of word meaning arises; it is possible to make sense of text when the meaning of some words is lacking or hazy, but beyond a modest level of uncertainty, comprehension becomes impossible.

Two types of processing occur (see figure 1): “bottom-up” and “top-down”. In bottom-up processing, words are formed into phrases, and phrases are formed into more abstract units called propositions or ideas; these processes require knowledge of syntax (grammar). Just as several words can be processed into one phrase, several phrases can be processed into one idea. Comprehension at the phrase or idea level results in a relatively shallow understanding of what the text stated directly, often termed literal comprehension. Further processing of these ideas either selects particular ones as main ideas, or constructs main ideas from them, and then thematic generalizations or abstractions out of the main ideas.

Top-down processing occurs when higher-level information, just as knowledge of the general topic of the text, helps the reader identify lower-level information. It is important to recognize that both bottom-up and top-down processing often occurs in reading comprehension. This is called interactive processing. The higher levels of processing require prior knowledge to help decide what is important, and especially to see the deeper implications of the text. Processing occurs in these levels to make best use of working memory resources. Working memory contains information or thoughts that we are currently aware of.

The ability to decode words is absolutely essential for skilled reading; those with very low decoding skills will be poor reading comprehenders.
However, listening comprehension, which represents verbal ability, is also essential. Verbal ability is a key component of intelligence, and may be very difficult to improve through instruction; it includes knowledge of vocabulary, grammar, the ability to make inferences, and so on. Decoding provides a more promising and fruitful target for instruction.

Two important factors beyond decoding and listening comprehension can be added: fluency and strategies. Fluency (speed and expression) is not an issue in listening as the speaker controls the pace, but it is needed for reading comprehension because of working memory limitations. If word recognition is slow, then previous words will have faded from working memory before later words are recognized, and their joint meaning will not be able to be processed.

Strategies are important in reading, and more useful than in listening, because the text stays present and allows re-inspections. Strategies are particularly useful when the text is long and/or complex, and the reader has many options about where to attend. We expect skilled readers to extract more from text than they would from speech, and some of that comes from strategic, goal-directed, deliberate processing.

Comprehension involves the relating of two or more pieces of information. Those pieces of information can come from long-term memory (prior knowledge), but in reading comprehension at least one piece must come from the text. The pieces of information can be simple or quite complex ideas, ranging from the word cat to the concept democracy.

For readers with rich knowledge, a word such as democracy evokes and brings to life many ideas without taking up additional working memory space; for readers with less relevant knowledge, the word itself may take up one or more spaces, with no additional information brought along “for free”. Children struggling to identify words are unlikely to be able to attain even modest levels of comprehension. When lower-level units are recognized automatically, there is a greater chance of higher levels being attained. It is critical to build up the automaticity of the lower-level units (e.g. words). It is equally important to remember that the processing of lower-level units does not guarantee the comprehension of higher level units.

• What factors contribute to the development of reading comprehension?
• Vocabulary knowledge and prior knowledge contribute to listening comprehension.
• It is difficult to see how readers can understand a text if there are many unknown words or concepts.

Over the last 25 years or so, we have learned a great deal about how the brain accomplishes the lower-level aspects of reading, especially decoding. We know that a number of factors contribute to word reading, including phonological awareness, naming speed orthographic knowledge, morphological awareness, and phonics knowledge (figure 2).

Fluency is less well understood, but clearly depends upon decoding efficiency, and cognitive and naming speed. As fluency drops, it becomes less and less likely that the needed information is still active in working memory, making comprehension less and less likely.

Reading comprehension strategies have been studied extensively.

There are 5 major strategies, each of which is associated with greater reading comprehension:

• determining importance,
• summarizing information,
• drawing inferences,
• generating questions, and
• monitoring comprehension.

None of these factors has much influence in the absence of motivation and interest. Most children are interested in reading when they begin school, but some can lose interest/motivation if their skills are not adequate or if the text content does not suit them.

“Poor comprehenders”

Children with lows levels of skill in the various contributing factors will struggle with reading comprehension, children with more areas of low skill will struggle more, and the more they struggle the more their interest will suffer, creating a vicious cycle. It is no secret that many children prefer other activities to reading, and that uninteresting text content can turn a capable reader into an unenthusiastic reader very quickly.

Reading comprehension is a complex process in itself, but it also depends upon other important lower-level processes. It is an important skill to target, but we should not forget about the skills on which it depends. To improve the reading comprehension skills of poor performers, we need to understand that there is no “magic wand” and no secret weapon that will quickly improve reading competencies for all poor readers.
Most poor readers will need continued support in many areas. The roots of most reading comprehension problems lie in the early years. The sooner we address them the better. •