Local and global processing in block design tasks in children with dyslexia or nonverbal learning disability

Visuo-constructive and perceptual abilities have been poorly investigated in children with learning disabilities. The present study focused on local or global visuospatial processing in children with nonverbal learning disability (NLD) and dyslexia compared with typically-developing (TD) controls. Participants were presented with a modified block design task (BDT), in both a typical visuo-constructive version that involves reconstructing figures from blocks, and a perceptual version in which respondents must rapidly match unfragmented figures with a corresponding fragmented target figure. The figures used in the tasks were devised by manipulating two variables: the perceptual cohesiveness and the task uncertainty, stimulating global or local processes. Our results confirmed that children with NLD had more problems with the visuo-constructive version of the task, whereas those with dyslexia showed only a slight difficulty with the visuo-constructive version, but were in greater difficulty with the perceptual version, especially in terms of response times. These findings are interpreted in relation to the slower visual processing speed of children with dyslexia, and to the visuo-constructive problems and difficulty in using flexibly-experienced global vs local processes of children with NLD. The clinical and educational implications of these findings are discussed.