Development and Initial Validation of an Expressive Vocabulary Test for Movement Concepts and Skills in Adults with Down syndrome
The present study aimed to develop and psychometrically evaluate the Expressive Vocabulary Test - Movement Concepts Skills - Down syndrome (EVT-MCS-DS) and to examine possible differences in expressive vocabulary performance according to demographic characteristics, including sex, living arrangement, and age group. The sample comprised 48 men and 18 women with Down syndrome (M age = 26.56 ± 2.80 years).The instrument was developed through a multi-phase procedure including the selection of 50 movement concepts and skills, their transformation into pictorial stimuli by an expert committee, item analysis (difficulty, discrimination, and point-biserial correlation indices), content validity evaluation, and reliability assessment (Cronbach’s α, Kuder–Richardson 20, split-half reliability, and test–retest stability). Item analysis resulted in the exclusion of 18 items due to unacceptable psychometric indices, yielding a final 32-item test. Internal consistency was high (Cronbach’s α = .952, KR-20 = .80, Spearman–Brown = .94), while test–retest reliability demonstrated excellent stability (ICC Single Measures = .967; ICC Average Measures = .983). Content validity was also supported (I-CVI = .80–1.00; S-CVI/Ave = .92). The EVT–MCS-DS demonstrates satisfactory initial evidence of validity and reliability and may serve as a useful tool for assessing expressive naming of movement concepts and motor skills in adults with Down syndrome.