From the distribution of the reaction time (RT), we intended to examine the normal standard process of essential psycho-somatic development as school grade advanced.
We investigated the phonating reaction times of repetitive tone click stimuli (20μ sec in duration, above 80db in strength) at irregular intervals of the city primary school children (from the 1st to the 6th, 246 persons) living in a calm residential area in Tokyo in 1967.
The results we obtained were not much differ from the data obtained 20 years ago by others.
The RT of primary school children were very variable temporally even in an experimental series of a same subject, especially in the lower grade children and the individual variation was also as much great.
This variability, however, was supposed to be the characteristic of the psycho-somatic growing process, so we examined the method of dealing with the figures of the RT paying great attention to the variability of it.
The results obtained were described in the form of histograms (ordinate-% trials of all in each group, abcissa-reaction time intervals of 50ms) and integration curves of the percentage of the total trials in successive reaction time intervals in each grade and sex group. From these distributions, it could be seen that the development was usually characterized by the faster and the more remarkable convergencies of the RT as the school grade advanced. And we confirmed that in integration curve, especially the following three factors, 1. reaction time in narrow sense, 2. intervals of deviation and 3. convergency, made apparent numerically the characteristic of the distribution of the RT and so displayed the trait of the developmental process in psycho-somatic function very clearly.
We examined, moreover, the characteristic of the RT of primary school children living the noisy region around jet air field, in comparison with the standard pattern of the psycho-somatic development of primary school children in Tokyo as mentioned above.
From the results, it was clearly observed that the noisy environment had much influence upon deviation and convergency of the RT and made the RT of children living in the noisy environment remain infantile pattern, preventing the RT from converging within shorter range and deviation of it from shortening as grade advanced.