The Use of Prior Knowledge in Reading

The key step in reading is to recognize the word by combining visually acquired letter information with prior knowledge of the possible words, as determined by narrative context and vocabulary. How are these two kinds of information combined to identify a word? The purpose of this project was to determine the effect that vocabulary size has on word identification. Vocabularies of 4, 26 and 1708 words were created. All words were four letters long and presented serially, one after another, at the same location using the Rapid Serial Visual Presentation (RSVP) paradigm. It is known that words can be recognized letter by letter or holistically, by overall word shape. The holistic process was knocked out, sparing the letter-by-letter process, by presenting the words in the peripheral visual field surrounded by clutter. Reading rate fell as vocabulary increased. At maximum reading rate, the time per word was approximately proportional to the log of the vocabulary size. Since letter recognition is serial, this indicates that when the vocabulary was small, observers could identify the word by identifying just one letter. As the vocabulary increased, observers had to identify 2 or even 3 letters to identify the word. This shows that readers do not simply get all the letters and then identify the word. Instead they get one letter at a time until they get the word. With more prior knowledge, fewer letters are needed.