String length of the brain evoked potentials (EPs) to an inspection time (IT) task was inversely related to IQ and mental speed as measured by the multidimensional aptitude battery IQ test and inspection time (IT) and reaction time (RT) measures of performance speed in a sample of 70 subjects. This findings is opposite to the relationship found in previous experiments, where cognitive processing was minimized. Processing efficiency and attention models were posited to account for rapid information processing accompanied by shorter string lengths among bright subjects. Nineteen channel topographic EPs from individuals differing on psychoticism (P), supported the claim that attention is a mediating variable in the string-IQ relationship. It is argued that previous experiments in this area should be reevaluated in terms of their demands on attentional resources.