The complications of reading and learning how to read can be lost on those who know how to do it. For many people, it's difficult to remember a time when they couldn't read, as many learn while very young. For young learners, or those who learn how to read later in life, the difficulties of reading are clear. To approach these difficulties, literacy experts theorize how reading happens and develop instructional models to help individuals master this complicated process.
Traditional theories of reading suggest it's a process by which individuals learn smaller, discrete words and parts of words before learning how to read whole sentences, paragraphs and so on. Traditional theories of reading maintain that individuals build up their vocabularies and grammatical rules, and through this act of accretion they slowly gather together the necessary components to read fluently. These bottom-up theories of reading lend themselves to models of instruction such as phonics-based learning, in which individuals sound out phonemes or parts of words and slowly combine them into whole words, whole words into sentences, and so on.
So-called cognitive theories of reading counteract traditional theories by maintaining that the concept and process of reading is learned first and then broken down into individual words, parts of words, sentences, paragraphs and so on. These top-down theories of reading believe there's a moment at which individuals understand the process of reading without being entirely familiar with all the discrete components of how to read, such as individual words, how words fit together, etc. Cognitive theories of reading lend themselves to models of instruction like the wholistic model that has individuals approach texts as a whole, even if they are not familiar with all the words or phrases or even how the words fit together into sentences. Through context clues and assistance, the wholistic model suggests students can eventually decode whole texts, which in turns allow them to decode that text’s individual components.
As the name suggests, hybrid theories of reading borrow liberally from both traditional and cognitive theories. In hybrid theories, reading is both a top-down and bottom-up approach in that as individuals approach whole texts and decode discrete components of those texts they also build up their vocabularies and personal understanding of grammatical rules which, in turn, helps them decode future whole texts -- which in turn builds their vocabularies and grammars. Hybrid models of reading, much as with hybrid theories of reading, encourage individuals to both compile lists or banks of phonemes, words, sentences and so on, as well as approach newer and more complicated whole texts as the individual learns how to read.
Metacognitive theories of reading relate to how an individual thinks about his reading processes both before, after and during the actual act of reading. Metacognitive theories of reading maintain that individuals, regardless of whether they approach reading from traditional, cognitive or hybrid theories or models of reading. Metacognitive theories of reading lend themselves to modeling practices such as written or spoken reflection following a reading exercise, as well note-taking on the margins of a page or highlighting lines or passages while reading.