The GDAP is the first standardized, computer-assisted, dynamic assessment of speech production and stimulability. This ground-breaking approach employs a unique 15-point cueing system and hierarchy (from 15 to 1) which represents the scaffolding levels available to a child in the production of a target. This responsive approach provides for a more sensitive measure that takes into account the emergence of skills and the child's ability to learn, not just the final speech product.
A standardized decision matrix is used to determine the progression of prompts and cues, and the speech environment complexity. A low score of “1” is best and indicates that the child produces the target sound independently (i.e. with no instructions or verbal cues) in connected speech. In contrast, a high score indicates that many support strategies were needed by the child for production of a single sound in isolation. By assessing a child’s responsiveness in greater detail with the GDAP, it is possible to measure how a child responds to cues across a range of systematically varied linguistic contexts.
The GDAP has 49 items, including 2 multisyllabic words, 22 initial phonemes, 21 final phonemes, 3 initial blends, and 1 final blend. Sound classes represented in the GDAP include:
- Glides
- Nasals
- Stops
- Velars
- Stridents
- Interdentals
- Liquids
Each item is tested in up to three speech environments using vibrant, child-friendly images:
- Single Word
- Two-Word Sentence
- Connected Speech
The GDAP was normed on a representative sample of 880 children ages 3.0 through 10.11.
Administration and Scoring
The GDAP is designed to be administered flexibly to get a comprehensive assessment of a child’s speech production or to document a child’s response to therapy for individual phonemes or sound classes. The clinician may administer the entire evaluation to a preschool-aged child with multiple errors; or the clinician may administer only specific test items as needed, such as the Liquid test items to an older elementary child with /l/ and /r/ errors.
Each target can be quickly administered in 2-3 minutes. The Phonemic Inventory which can be administered prior to the GDAP to document the phonemes already in the child’s repertoire, thereby reducing testing time.
Criterion-based scores are provided for each item and can be further analyzed using frequency and age of mastery tables. Sound Classes are reported as scaled scores and percentile ranks, and the Overall score is reported as a standard score and percentile rank. Standard scores are also available for Initial and Final Position Phonemes. Significant changes in score can be documented using the Reliable Change Index.
The GDAP matrix can be administered via paper and pencil, or easily through the ATP Online interface.
Reliability and Validity
- Cronbach’s Alpha values ranged from 0.71 to 0.93 for individual Sound Classes and was 0.95 for the Overall score.
- Test-retest correlations were 0.98 to 0.99 for the Sound Class and Overall scores.
- Correlations between computer-assisted and paper-based administrations ranged from 0.94 to 0.99 for the Sound Class and Overall scores.
- A cut-off Overall standard score of 90 yielded a specificity of 0.80, sensitivity of 0.77, and an AUC of 0.88.
- Validity studies demonstrate that individuals with speech sound disorders had significantly lower scores on the GDAP than their demographically matched peers.
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