Cardiac and respiratory responses during visual search in nonretarded children and retarded adolescents.

The relationship between physiological response patterns and mental competence was investigated by evaluating heart rate and respiratory responses during a sustained visual-search task in nonretarded grade school children and retarded adolescents. The findings support the contention that, during tasks demanding sustained attention, retarded relative to nonretarded individuals exhibit physiological responses that parallel their poor performance. Consistent with previous research with nonretarded adults, the nonretarded grade school children exhibited a suppression of respiratory and heart-rate variability during attention-demanding tasks. In contrast, the retarded adolescents exhibited increases in respiratory and heart-rate variability. These qualitative differences in physiological and behavioral responses, observed during sustained attention, may be viewed as a manifestation of retarded adolescents' defective nervous system.