Tactile-visual equivalence of shape and slant in brain-damaged and mongoloid children.

Earlier, we reported on the development in children of the ability to equate stimuli written o p the back with visually presented equivalents (Kennedy & Sheridan, 1972) . Here, we describe the performances of brain-damaged and mongoloid children on the same. two-choice tasks involving discrimination between mirror-image oblique lines oriented 45" to the right vs left or between a triangle vs a circle. The stimulus chosen from a given pair was presented either visually or by tactile drawing on a cloth template placed on the back. Locus of tactile presentations of slant stimuli was varied-either right, left or middle of the back. Tactile and visual stimuli were identical in size, shape, and orientation. Order of presentation of slant and shape tasks was varied haphazardly across children. Matching from sample was always done by selecting one from the visually presented pair, the standard being varied randomly from trial to trial. A guess rate was obtained for each stimulus pair by eliminating presentation of the standard on certain trials. There were three groups of Ss: (1) a group diagnosed as "brain-damaged," ranging in age from 12 to 13 yr. (N = 8 ) , ( 2 ) a group oE mongoloids ages 11 to 14 yr. (N = 3 ) , and (3) a group of "normal" children ranging from 7 to 13 yr. of age. The brain-damaged and mongoloid children attended a school for trainable children and had IQs, measured by the Stanford-Binet Intelligence Test, ranging from 25 through 50. Performances of normal children were between 92% and 100% correct on all conditions except the guess-rate condition, which yielded 50% correct. Thus, normal children readily match to sample regardless of modality, stimulus type, o r locus on the back. Mongoloids performed essentially at chance levels on all conditions except that requiring visualto-visual matching with triangle vs circle stimuli, for which the mean performance was 97% correct. Thus, they could neither perform cross-modal equivalence testr, nor match to a visual sample when slant was the dimension being discriminated. Except for the abovementioned triangle-circle, visual-to-visual condition and the guess-rate condition, there was no overlap between mongoloid and normal children. There was also no overlap between scores of brain-damaged and normal children, except for visual-to-visual triangle-circle and guess-rate conditions. W i t h the same two exceptions, mean scores were slightly higher in all conditions for brain-damaged than for mongoloid children, though overlap berween the two classes of impaired children was substantial. Whether brain-damaged or mongoloid, impaired children tended to show their worst performance when slant stimuli were presented to the left of the back. In fact, the highest level of performance obtained was by one child (brain-damaged) who reached the 50% level. This indicates that the impaired Ss tended to select the reverse orientation when matching from a slant sample presented to the left back. It is interesting that, despite the high level performances of normal children, this was the worst condition for them as well, half of them falling below the typical 100% correct under this condition.