A study was conducted that attempted to show changes in electroencephalographic (EEG) patterns (identified using topographic EEG mapping) when children were required to perform the relatively simple task of button pressing during an eyes-open baseline session of low cognitive demand and a complex reaction time (RT) task of high cognitive demand. Subjects were four male and five female 10- to 12-year-old children. One of the boys was left-handed. Using past research, EEG patterns recorded two seconds prior to the button push for both conditions were analyzed into component frequencies using a Fast Fourier Transform algorithm. Results show a statistically significant decrease in beta activity during the performance of the more cognitively demanding task relative to the simple condition. Topographic and statistical probability maps suggested that this decrease occurred primarily in the frontal lobe of the left cerebral hemisphere and in the temporal and parietal lobes of the right hemisphere. Results are explained in terms of past EEG research, and possible psychophysiological applications to cognitive and educational research are discussed. Six figures illustrate the discussion. (Author/SLD)