EVALUATION OF A MENTAL EFFORT HYPOTHESIS FOR CORRELATIONS BETWEEN CORTICAL METABOLISM AND INTELLIGENCE

Previous research indicates that low scores on the Raven's Advanced Pr ogressive Matrices (RAPM) test are associated with increased cortical glucose utilization during problem solving. We hypothesized that previ ous results may reflect the neurophysiological consequences of pattern s of effort requirements; that is, high-effort expenditure from lower aptitude participants (for whom the problems are hard) and low-effort expenditure from higher aptitude participants (for whom the problems a re easy). In this experiment, positron emission tomography (PET) data were gathered on participants (N = 28) who solved easy and hard proble ms that were tailored to the participants' own ability levels, thereby eliminating aptitude group differences in effort requirements. Contra ry to previous results, high aptitude was associated with high cortica l glucose use. Average aptitude participants showed diminished glucose use in the hard condition. A significant Group x Condition x Hemisphe re Effect was also noted, with greater right hemisphere activation in the hard condition for the high-aptitude group. These results demonstr ate that the relation of cerebral glucose use and cognitive ability is sensitive to participant and task selection.