Event-related potentials reflect various cognitive functions and include the mismatch negativity and P300. The mismatch negativity is said to reflect the process in which stimuli are detected automatically. The mismatch negativity requires no concentration of attention or understanding of the subject, and is useful for objectively evaluating the cognitive ability in newborns. The P300 wave is generally interpreted as a neural correlate of decision-making or of signal detection by an actively attentive subject. Studies of event related potentials in children, based on a task relevant oddball paradigm, reveal a decrease in the latency of P300 with increasing age. This developmental change could be related to maturation phenomena in cognitive processes. Squires et al. delineated P3a and P3b components in P300. In our study, P300 in a state of ignoring, likely corresponds to P3a (passive attention), whereas conventional P300 corresponds to P3b (active attention). These findings indicate a developmental difference between the P3a and P3b potentials. The development of fundamental cognitive function like passive attention reaches the adult level at an earlier age than the cognitive-like active attention. To evaluate auditory spatial cognitive function, age correlations for event-related potentials in response to auditory stimuli with a Doppler effect were studied in normal children. From the age of 4 years, the P300 latency for the enlarged tone with a Doppler effect shortened more rapidly with age than did the P300 latency for tone-pips, and the latencies for the different conditions became similar towards the late teens. These findings provide evidence that auditory cognitive function, including auditory spatial cognitive function, had reached the adult level by about this age. P300 in response to different stimuli may provide more detailed information that could enable the evaluation of cognitive function development in children.