Measuring how young children grow their vocabulary is very important. Researchers need this information to understand how language develops, and doctors use it to find language problems early on. The MacArthur-Bates Communicative Development Inventories (CDIs) are tools that parents use to report on their children’s language. They are known to be a good way to measure early vocabulary in many languages, both what children understand (receptive) and what they say (productive). However, CDIs usually have many words, making them long to complete. To make them easier to use, we created shorter, computer-based versions called CDI-CATs, using a method called item response theory (IRT). We made CDI-CATs to measure both understanding and speaking vocabulary, in both American English and Mexican Spanish.
To create these CDI-CATs, we used information from a large group of children. We had data from 7,633 English-speaking children (ages 12-36 months) and 1,692 Spanish-speaking children (ages 12-30 months). These children had been tested using three different CDI forms (Words & Gestures, Words & Sentences, and CDI-III). We looked at 680 vocabulary items from these forms and found that a 2-parameter logistic IRT model worked well for most of them. Then, we simulated using CATs with this data, testing different lengths of tests, from 25 to 400 items.
The results showed that even very short CATs were able to accurately measure children’s vocabulary skills, no matter their age. To check if this worked in real life, we tested 204 children ages 15-36 months. We found a strong connection (r = .92) between the vocabulary skills measured by the full CDI and the CDI-CAT forms. This means the CDI-CATs are a good, shorter way to get the same information.
In conclusion, we are sharing the list of words we used, along with other details for those who want to create CDI-CATs in new languages. We also offer advice on when this type of test might be useful. These CDI-CAT tools offer an efficient way to assess vocabulary in both English and Mexican Spanish, aiding in both research and clinical practice by reducing the burden of traditional, longer assessments.
