||Studying human information processing allows researchers to better understand the operations of the human brain. While a large body of research has used reaction times and cognitive correlates to quantify information processing, electrophysiological correlates improve knowledge of cortical activity. Using an elementary cognitive task, this study examined the manipulation of information processing demands on reaction times and event-related potentials, and how these are related to intellectual ability. Forty healthy adults completed a choice-reaction time EEG task manipulating the number of alternative responses. EEG potentials were recorded relative to a warning stimulus and a subsequent stimulus prompting a response. Reaction times were recorded as the time from the response stimulus to the completion of a button push. ERPs and scalp maps showed a low-frequency, lateralized negativity between the two stimuli, indicating that the task elicited the Contingent Negative Variation potential. The number of alternative choices were found to have a significant effect on reaction times [F(1.419,55.334) = 71.679, p < .01)] and on the CNV negativity [(F(1.787,69.69) = 12.282)], indicating that increased information processing demands resulted in longer reaction times and less negativity in the CNV. Negative correlations were found for intelligence and reaction time (r = -.37, p < .05), and with CNV (r = -.196) but the latter did not reach significance. Regression slopes of reaction times and the CNV positively correlated (r = .352, p < .05). These results suggest that additional processing demands limit neural preparation for responses and produce longer response times. Individuals with higher FSIQ scores were also more likely to have faster reaction times, and while the relation between IQ and CNV was in the same direction but not significant, this suggests a similar process. The relation between slopes of reaction times and the CNV implies a connection of intelligence facilitating greater neural preparation, thus increasing response times. These findings provide an important bridge of cognitive ability and physiology to better understand information processing and intelligence.