Construction and standardization of non-verbal learning disability (NLD) test in Iranian primary school students

Nonverbal learning disability is considered a specific indicator of learning and reasoning. The current research aimed to develop and validate a total scale for assessing nonverbal learning disabilities in elementary school students. Using a sequential exploratory mixed-methods design, a total of 147 students with nonverbal learning disabilities and 198 typically developing students from grades one to six were selected, encompassing both genders. The average age of the patients was 9 years and 6 months. The designed test was a performance-based neuropsychological test battery consisting of 12 subscales extracted on the basis of theoretical foundations and existing research background in the field of nonverbal learning disabilities. Research findings indicated that the scale demonstrated adequate reliability, with a Cronbach's alpha value of 0.92 achieved for the total scale. Additionally, the fit indices and confirmatory factor analysis results demonstrated that the scale possessed appropriate structural validity. The discrimination validity results suggested that the total test score effectively differentiated students with nonverbal learning disabilities from typically developing students. On the basis of a norm-referenced percentile analysis of the sample, grade-specific clinical cutoff scores and performance categories were established, demonstrating the tool's diagnostic utility. On the basis of the research findings, it can be concluded that the developed scale exhibits sufficient validity and reliability, serving as a valid tool for diagnosing nonverbal learning disabilities.