FLUID INTELLIGENCE AFTER FRONTAL-LOBE LESIONS

Generally positive correlations between different ability tests provid e the evidence for a factor of ''general intelligence'' or Spearman's g. Though a possible neural substrate for g is suggested by executive impairments following frontal lobe lesions, preserved IQs in some fron tal patients have been taken as strong evidence against this interpret ation. We show that such results depend on how g is measured. Patients with superior IQs on the most clinically popular test-the Wechsler Ad ult Intelligence Scale-show impairments of 20-60 points on conventiona lly measured fluid intelligence or novel problem solving. On psychomet ric grounds, it is fluid intelligence that is most closely related to Spearman's g. The data suggest that g may in large part be a reflectio n of frontal functions.