Stimulability: auxiliary measure in the identification of difficulty in speech sounds production

To analyze the effectiveness of stimulability as a complementary task to the diagnosis of speech sound disorders (SSD), and to describe the performance of children with absent sounds from the phonetic inventory according to stimulable absent sounds, severity, gender, age, and occurrence of different phonological processes.

Participants were 130 male and female children with ages between 5 years and 10 years and 10 months, divided into two groups: Research Group (RG), comprising 55 children with SSD; and Control Group (CG), composed of 75 children with no speech and language disorders. Based on participants' performance on the Phonology test, the severity of the disorder was calculated through the Percentage of Consonants Correct - Revised (PCC-R), and the phonetic inventory was verified. The stimulability test was applied to each absent sound from the phonetic inventory, based on the imitation of single words. The RG was subdivided into RG1 (27 children who presented absent sounds) and RG2 (28 children with complete inventory).

None of the CG children presented absent sounds in the phonetic inventory, while 49% of the RG1 subjects presented absent sounds. There was absence of most language sounds. PCC-R means were lower for RG1, indicating higher severity. In the RG1, 22 children were stimulable, while five were not stimulable to any absent sound. There was association between the most occurring phonological processes and the need for stimulability assessment, indicating that the difficulty to produce absent sounds reflects difficulty with phonological representation. Stimulability is influenced by age, but not by gender.

The stimulability test is effective to identify stimulable children among those who present absent sounds from their phonetic inventory. Children with SSD and absent sounds have lower PCC-R, and therefore present more severe disorder. Most of the children with absent sounds are stimulable, but may not be stimulable for complex syllable structures or articulatory gestures. The difficulty to produce absent sounds reflects phonological representation deficit. Speech production is influenced by maturation in both boys and girls.