We compared 32 children with spina bifida and 31 age-matched controls on tw
o classes of illusory perception, one involving visual illusions and the ot
her, multistable figures. Children with spina bifida were as adept as age p
eers in the perception of visual illusions concerned with size, length, and
area, but were impaired in the perception of multistable figures that invo
lved figure-ground reversals, illusory contours, perspective reversing, and
paradoxical figures. That children with spina bifida reliably perceive ill
usions that rely on inappropriate constancy scaling of size, length, and ar
ea suggests that their brain dysmorphologies do not prevent the acquisition
of basic perceptual operations that enhance thr local coherence of object
perception. That they do not perceive multistable figures suggests that the
ir visual perception impairments may involve not object processing so much
as poor top-down control From higher association areas to representations i
n the visual cortex. (C) 2001 Academic Press.