Oral vocabulary, or knowledge of word meanings, plays a key role in reading comprehension. If children are unfamiliar with the meanings of words in a text, their comprehension will suffer, even if they can decode the words. For example, if a child can sound out the printed word scarlet in a sentence but does not know that scarlet means red, some comprehension will be lost; if this experience is repeated with a number of important words in the text, then comprehension will be seriously impaired.
Although vocabulary is critical to reading at all stages of development, the vocabulary demands of the texts used in school escalate greatly beginning at about a fourth-grade level. Therefore, children with vocabulary weaknesses are especially vulnerable to difficulties with reading comprehension from the middle elementary grades onward. Furthermore, vocabulary weaknesses may affect school achievement in many areas beyond reading, including written expression, mathematics, and performance in content subjects such as social studies and science.
Vocabulary and learning disabilities
Vocabulary knowledge varies greatly in individuals with learning disabilities (LDs). For some youngsters with LDs, vocabulary can be an area of strength. For instance, children with dyslexia or specific reading disabilities may have above-average oral vocabularies despite having phonological weaknesses that adversely affect the development of decoding skills. These youngsters may have excellent listening comprehension, as well as the ability to dictate stories with strong verbal content.
For other children with LDs, such as those with more generalized language difficulties (but typically average or better nonverbal abilities and social functioning), vocabulary weaknesses can be part of a broader language impairment. Of course, vocabulary knowledge for individuals with LDs also is affected by experience and opportunities to learn new words, just as it is for all children. For example, whether or not they have learning disabilities, children who are often read to at home and whose teachers address vocabulary in instruction will have more exposure to words and better prospects for vocabulary development.
Assessment of vocabulary
Assessment of vocabulary is critical for identifying children at risk for reading problems and for designing appropriate instruction. The use of oral measures is essential. Tests that require reading or writing make it impossible to differentiate other problems children may have, such as difficulties in word decoding or spelling, from lack of vocabulary knowledge. Children with suspected learning disabilities should be individually assessed on measures that include both receptive and expressive oral vocabulary. Receptive vocabulary involves understanding of spoken words, for instance, asking a child to point to a picture that represents a word spoken by the examiner. Expressive vocabulary involves using or naming a word, as when the examiner shows a picture to a child and asks the child to name it. Although the relationship of receptive vocabulary to reading comprehension seems obvious, expressive vocabulary appears to be an even stronger predictor of beginning reading achievement than is receptive vocabulary. Therefore, both areas should be included in a comprehensive assessment.
Researchers interested in vocabulary instruction have examined direct and indirect approaches to teaching vocabulary. Direct approaches involve explicit teaching of new word meanings, whereas indirect methods encourage inferring word meanings from context. Currently there is considerable consensus that explicit vocabulary instruction is highly desirable for children in general, and especially important for youngsters with learning disabilities. Vocabulary instruction should involve many opportunities to use new words, to discuss words, and to compare new words with previously learned words.
In addition, children should be taught how to employ resources such as glossaries, dictionaries, and thesauruses, including electronic and online resources. Although direct instruction in vocabulary is imperative, students also benefit from learning to use context to determine word meanings, as well as from opportunities to see and hear how words tend to be used. For example, the words segregate and sequester both mean to isolate, but sequester is often used in a legal context (sequestering a jury) and segregate in the context of separation by race or gender. Similarly, students need to understand different connotations of words; thrifty and miserly have related meanings but quite different connotations. Vocabulary instruction should target at least two broad categories of words: unfamiliar vocabulary with high generalizability across texts (i.e., words that are likely to recur in different contexts), and those necessary for understanding specific texts used in school (e.g., key terms necessary for comprehension of context area textbooks).
Studies that have focused specifically on vocabulary instruction for students with LDs have found a number of approaches to be helpful for this population, including teaching keyword mnemonic strategies (i.e., a “word clue” involving imagery for each vocabulary word); meanings of word parts such as common roots, prefixes, and suffixes; and mapping techniques, such as drawing word maps to illustrate central concepts. As students advance beyond beginning levels of reading, vocabulary instruction should be integrated with decoding and spelling instruction. For example, at the same time that students learn that the prefix tele means distant (as in telephone, telegram, telepathy, telemarketing, etc.), they also read it and learn that its spelling is generally stable; therefore, the word for the object on which they watch their favorite shows must be television, not telivision or telavision.
Students whose learning disabilities affect broad language and vocabulary acquisition will need a particular emphasis on vocabulary learning. For other students with LDs, vocabulary may be a strength upon which instruction should capitalize. Nevertheless, as a fundamental component of literacy and content learning throughout formal schooling, vocabulary must be addressed as part of the curriculum for all students. Ongoing assessment of vocabulary and appropriately targeted instruction are therefore essential, whether or not students have learning disabilities.