Early vocabulary growth is crucial for language development and identifying potential language delays in young children. The MacArthur-Bates Communicative Development Inventories (CDIs) are parent-report questionnaires used to measure vocabulary in toddlers. However, these forms often contain hundreds of words, making them time-consuming to complete. This study leveraged Item Response Theory (IRT) to create Computer Adaptive Tests (CATs) for both English and Mexican Spanish, significantly reducing testing time while maintaining accuracy.
Shorter Tests, Accurate Results: The CDI-CAT
Traditional CDIs, while effective, can be lengthy. This research aimed to develop shorter, more efficient versions – CDI-CATs – for assessing both comprehension (understanding words) and production (speaking words) in both American English and Mexican Spanish. These adaptive tests adjust the difficulty level based on the child’s responses, allowing for precise measurement with fewer questions. The team used a vast dataset comprising 7,633 English-speaking children (12-36 months) and 1,692 Spanish-speaking children (12-30 months) across three CDI forms.
Developing the CDI-CAT: A Statistical Approach
A 2-parameter logistic IRT model was applied to analyze 680 vocabulary items across the CDI forms. This model effectively determined the difficulty and discriminatory power of each word. CAT simulations were then conducted to evaluate the accuracy of tests with varying lengths (25-400 items). The results showed that even short CATs accurately estimated vocabulary abilities across different age groups.
Validating the CDI-CAT in Real-World Testing
To confirm the accuracy of the CDI-CAT, a study with 204 children aged 15-36 months was conducted. The children were assessed using both the full CDI and the CDI-CAT. The correlation between the two tests was remarkably high (r = .92), demonstrating that the shorter CDI-CAT provided results comparable to the full CDI. This validation study confirmed the effectiveness and reliability of the CDI-CAT in a real-world setting, paving the way for its use in assessing vocabulary development in young children.
Implications for Vocabulary Assessment
This study provides a significant advancement in vocabulary assessment for young children. The development of CDI-CATs for both English and Mexican Spanish allows for efficient and accurate measurement of language abilities, potentially improving early identification of language delays. The researchers also offer guidelines for developing CDI-CATs in other languages, expanding the potential reach of this valuable tool. This innovative approach to vocabulary testing promises to facilitate research on language acquisition and improve clinical practice in identifying children who may benefit from early intervention services. The complete item bank, fitted parameters, and recommendations for creating CDI-CATs in new languages are available for researchers and clinicians. Further research is needed to determine the suitability of CDI-CATs in diverse populations and specific clinical contexts.
