We have previously shown that temporal integration in the domain of a few seconds may be studied using a subjective accentuation paradigm. Here we report developmental effects on the limits of this temporal integration in 9-10-year-olds in comparison with 13-14-year-olds. The task was to listen to a string of identical metronome beats and mentally bind the presented beats by subjectively accentuating every second, third or nth beat. The integration interval length was defined as the number of stimuli mentally connected multiplied by the temporal interval between two successive beats. For the lowest stimulus frequency integration intervals were approximately 3 s for the older and 2.2 s for the younger children. For higher frequencies integration intervals got systematically shorter, but being always longer for the older age group. It is suggested that the prefrontal region is responsible for this developmental effect. The expansion of temporal integration correlates with cognitive development in the investigated phase of ontogenesis.