Researchers have devoted considerable attention to how people learn to read, specifically how they recognise, pronounce, and understand printed words. These studies are helping to illuminate not only the normal process of learning to read but also the problems that may underlie dyslexia, a condition in which people are unable to acquire a high degree of reading skill despite adequate intelligence and training. When reading instruction begins, children (as well as adult learners) already possess large spoken-word vocabularies. Their initial task is to learn how these spoken words correspond to written alphabetic symbols. Impairments in this reading skill are often seen among children who have problems learning in school. Dyslexia is a brain-based type of learning disability that specifically impairs a person's ability to read. These individuals typically read at levels significantly lower than expected despite having normal intelligence. Although the disorder varies from person to person, common characteristics among people with dyslexia are difficulty with phonological processing (the manipulation of sounds) and/or rapid visual-verbal responding.