VOCABULARY DEVELOPMENT

Critical to the development of language is the ability to acquire words, determine what they mean, store them in the lexicon and access them for language use.  Difficulties with the acquisition of vocabulary and building of the lexicon have been noted in the language characteristics of deaf and hard of hearing children.   Therefore, it is critical for the child to establish the basic elements of the lexicon and begin to expand the memory system from sensory images to verbal symbols.  In order to explore the emergence of vocabulary, comparisons between development of children who hear and children who are deaf and hard-of-hearing will be compared.

Critical to the development of language is the ability to acquire words, determine what they mean, store them in the lexicon and access them for language use.  Difficulties with the acquisition of vocabulary and building of the lexicon have been noted in the language characteristics of deaf and hard of hearing children.   Therefore, it is critical for the child to establish the basic elements of the lexicon and begin to expand the memory system from sensory images to verbal symbols.  In order to explore the emergence of vocabulary, comparisons between development of children who hear and children who are deaf and hard-of-hearing will be compared.

The acquisition of word knowledge is the foundation of semantic knowledge.  This human child’s begins to acquire verbal symbols or words at approximately twelve months of age and spends the subsequent years in childhood amassing significant quantities of words and word classes.  Hearing loss has been found to have a significant negative impact upon the development of word knowledge in children with hearing loss, not only in quantity but also in the elaboration of the concept.    Characteristics of the vocabulary deficit are the most significant predictors of success in reading and writing.   The amount of words in the lexicon, the ability to define words, to associate words, to produce synonyms and antonyms, to spontaneously produce verbal labels and to correctly identify pictures corresponding to a verbal label have all been found to be highly associated to the ability to read.

Studies of typical language development have reported both size of the lexicon as well as type of words in the lexicon. Bates and colleagues have published the MacArthur Communicative Development Inventory with norms from over a thousand infants and toddlers below the age of thirty months.  The average eighteen month old has approximately 50 expressive words, the average twenty-one month old has about two hundred words, the average twenty-four month old has approximately 300 words and the average thirty month old has approximately 600 words.  This assessment instrument has been found to be both reliable and valid in various studies of infants and toddlers from over one thousand families.

The 75th%ile of early-identified children with hearing loss (as measured by the MacArthur-Bates Communicative Development Inventories) have vocabulary production at the median of the distribution for hearing children. A number of the children with significant hearing loss achieve age appropriate vocabulary inventories by three years of age.  The 75th%ile of the later-identified children is below the 25th%ile of the distribution for hearing children.  Children identified with hearing loss at birth are more likely to exhibit age appropriate vocabulary development than those identified after six months of age (Yoshinaga-Itano & Apuzzo, 1995).

DESCRIPTION OF THE MACARTHUR-BATES COMMUNICATIVE DEVELOPMENT INVENTORIES (CDI)

MacArthur-Bates Communicative Development Inventories (CDI), Second Edition (Fenson, Marchman, Thal, Dale, Reznick & Bates, 2006).

• There are three different versions of the CDI, one for infants from 6 to 18 months, one for toddlers from 18 to 30 months, and one for children from 30 to 37 months.

• The infant form assesses receptive and expressive vocabulary as well as the use of communicative and symbolic gestures.

• The toddler form assesses productive vocabulary, and the early phases of grammar.  The most advanced form evaluates vocabulary production and grammar.

• Each of these forms has been modified in our laboratory so as to assess spoken and signed vocabulary separately.

• Extensive testing reveals good internal consistency (alphas from .67 – .96) and test-retest reliability (.86 – 95) (See Dale, Bates, Resnick, & Morriset, 1989).

• Children should be given the appropriate version of the MacArthur depending on the family’s and interventionist’s assessment of the child’s language ability.

• The inventories are parent-completed, norm-referenced instruments based on the performance of 1,789 normally developing infants and toddlers 8 to 30 months of age.

Words and Gestures [Link]

1. Gestures Used
2. Words Understood
3. Phrases Understood
4. Words Produced
5. All slides

Words and Sentences

1. Words Produced
2. Irregular Nouns/Verbs Produced
3. All slides

MacArthur III

1. Words Produced – Vocabulary
2. Language Usage
3. Sentence Complexity
4. Irregular Nouns/Verbs Produced
5. All Slides

Norms across all three assessments can be accessed by group:

1. Total Group
2. By Age of Identification
3. By Degree of Hearing Loss
4. By Cognitive Level
5. By Age of Identification and Cognitive Level