Is the prefrontal cortex important for fluid intelligence? A neuropsychological study using Matrix Reasoning.
Patients with prefrontal damage and severe defects in decision making and emotional regulation often have a remarkable absence of intellectual impairment, as measured by conventional IQ tests such as the WAIS/WAIS-R. This enigma might be explained by shortcomings in the tests, which tend to emphasize measures of "crystallized" (e.g., vocabulary, fund of information) more than "fluid" (e.g., novel problem solving) intelligence. The WAIS-III added the Matrix Reasoning subtest to enhance measurement of fluid reasoning. In a set of four studies, we investigated Matrix Reasoning performances in 80 patients with damage to various sectors of the prefrontal cortex, and contrasted these with the performances of 80 demographically matched patients with damage outside the frontal lobes. The results failed to support the hypothesis that prefrontal damage would disproportionately impair fluid intelligence, and every prefrontal subgroup we studied (dorsolateral, ventromedial, dorsolateral + ventromedial) had Matrix Reasoning scores (as well as IQ scores more generally) that were indistinguishable from those of the brain-damaged comparison groups. Our findings do not support a connection between fluid intelligence and the frontal lobes, although a viable alternative interpretation is that the Matrix Reasoning subtest lacks construct validity as a measure of fluid intelligence.
Tranel
Daniel
D
Department of Neurology, University of Iowa Hospitals and Clinics, Iowa City, Iowa 52242, USA. daniel-tranel@uiowa.edu
Manzel
Kenneth
K
Anderson
Steven W
SW
D000368:Aged; D001925:Brain Damage, Chronic / Q000473:pathology*; D016022:Case-Control Studies; D003657:Decision Making; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007360:Intelligence; D007361:Intelligence Tests; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D017397:Prefrontal Cortex / Q000473:pathology / Q000503:physiopathology*; D011340:Problem Solving / Q000502:physiology*; D014705:Verbal Behavior