SUBTYPING OF DEVELOPMENTAL MOTOR DEFICITS

The purpose of this study was to investigate whether subtypes of developmental motor deficits could be identified: specifically, one with impairments in motor planning that would be characterized by deficits in gestural performance and motor sequencing and a second with impairments in the execution of motor skills that would be characterized by deficits in balance and coordination. Subjects included 102 children between the ages of 6 years and 10 years, 11 months, 51 who had been identified as displaying deficits in motor skills and 51 normal controls. Hierarchical-agglomerative and iterative partitioning cluster analyses using measures of balance, bilateral coordination, upper limb coordination, transitive gestures, and motor sequencing revealed four subtypes. One group displayed deficits in motor sequencing, whereas another demonstrated deficits in balance, coordination, and gestural performance. In addition, a third group of children showed severe deficits in all motor skill areas, and a final group had no motor deficits compared with the other groups. Examination of performance on measures of academic, language, visual-perceptual, visual-motor skills revealed that these four groups displayed different patterns of nonmotor performance. These findings suggest that different subtypes of developmental motor deficits can be identified among children who have been labeled ''clumsy.''