Nonverbal intelligence and the speed/accuracy trade-off in children with diabetes: A longitudinal follow-up
Description
The present longitudinal study examined Wechsler Performance Scale IQs, along with speed of responding and accuracy of a variety of visuospatial and graphomotor tasks, in a cross-regional sample of children with Insulin-dependent Diabetes Mellitus (IDDM; $n=143)$ and a matched group of controls $(n=101),$ both of whom were re-evaluated an average of 3.2 years after initial evaluation. With a subject retention rate of 83 percent, children with diabetes were 15.6 years at the time of follow-up. Evidence of 17 percent slower responding was found for adolescents with diabetes compared to controls at follow-up on a PIQ aggregate time variable, despite similar performance accuracy for both groups. Results revealed that speed of responding remained static over time for adolescents with diabetes and did not improve like that of controls. This pattern of static diabetic speed and preserved accuracy across time was primarily attributable to 24 percent slower performance by IDDM adolescents on the Picture Arrangement subtest, which may serve as a measure of fine visual discrimination skills in postpubertal adolescents with diabetes. Adolescents with diabetes also were significantly slower than controls by 14 percent on the Object Assembly subtest at follow-up, suggesting that slower responding had generalized beyond visual discrimination skills alone to speed of processing of other cognitively complex visual information, although again, accuracy was preserved. Evidence also was found of slowed fine motor skills, as reflected on the Grooved Pegboard (GP). The GP results exhibited greatest performance disruption for adolescents with diabetes; their performance became significantly slower, and failed to improve in accuracy across time, in contrast to the pattern of controls. In toto, the results from this study suggest that the slower diabetic performance found relative to controls in middle adolescence appears circumscribed and do not involve significant higher order CNS functioning, as reflected by intelligence test scores at follow-up. Evidence further suggests that slower diabetic performance may be attributable to primary sensory and motor CNS involvement, as detected by poorer visuospatial and fine motor skills