“…A number of studies have compared tonic skin conductance levels (SCLs) of subjects classified as hyperkinetic, minimally brain dysfunctional, and learning disabled with groups of matched controls. Only one study (Satterfield & Dawson, 1971) found that hyperkinetic subjects have significantly lower SCLs than controls, and five studies failed to find SCL differences between controls and children with MBD (Boydstun, Ackerman, Stevens, Clements, Peters, & Dykman, 1968;Zahn, Abate, Little, & Wender, 197S), children with learning disabilities (Rugel & Rosenthal, 1974), hyperkinetics (Cohen & Douglas, 1972), or hyperkinetics who respond positively to methylphenidate (Spring, Greenberg, Scott, & Hopwood, 1974). Similarly, two studies reported that hyperkinetic children have significantly lower base rates (Conners, 1975;Forges, Walker, Korb, & Sprague, 1975), and two studies reported no heart rate differences between hy-perkinetic subjects and controls (Boydstun et al, 1968;Zahn et al, 1975).…”