To investigate the covert behavior of children during the warning intervals of simple RT task, cue stimuli consisting of a combination of temporal (regular vs. irregular) and spatial presentation (regular vs. irregular) were introduced in the warning interval. First-5th grade children performed under these condition. The effects of temporal factor were significant for 3rd, 4th and 5th graders but were not significant for 1st and 2nd graders. On the contrary, the effects of spatial factor were more marked for 1st, 2nd and 3rd graders than for 4th and 5th graders. These results suggested the developmental changes in the covert behavior performed by children.