Impaired visual perceptual performance on an object recognition task in children with cerebral visual impairment

Visual perceptual ability and grating acuity were studied in 22 children with cerebral visual impairment (CVI). In most studies indicating visual perceptual impairments in CVI children, the evidence is weakened by the co-presence of reduced nonverbal, relative to verbal, intelligence, which in itself might account for the impaired performance on visual perceptual tasks. Our aim was to show that CVI children's performance on a visual perceptual task is weaker than can be expected from their nonverbal intelligence scores, thus demonstrating an impairment that is specific to visual perception. To this end, we used an object recognition task consisting of 60 line drawings depicting common objects in various aberrant ways. For each drawing, the age was established at which 9 out of 10 normal children could recognise the object depicted. This information was used to select the subset of drawings appropriate for each of the CVI subjects' nonverbal intelligence level, expressed as an age equivalent. Recognition performance on this subset of drawings was impaired in 16 children (72.7%), but was unrelated to visual acuity. We conclude that these children have a specific visual perceptual impairment, which is not reducible to any nonverbal intelligence impairments they might suffer.