In Tables 1∼3 are shown the relations between the amount of information and the output in a spell of 45∼60 minutes mental work. The output decreases with duration of working and its reduction grows remarkable with increased amount of information. Another date obtained in an experiment carried out to examine the variability of children's ability in recognizing spatial patterns (Fig. 1) during school hours gave the same evidence, the decreases of ability that occurs in the last hour was found more remarkable when the pattern's amount of information becomes larger. In Tables 4∼6 are shown that the respiratory rate and pulse rate ascend significantly with large amount of information, while slightly with small one. These evidence indicate that the more the amount of stimulus information, the greater are the degree of fatigue-symptom and impairment. Following evidences, such as that shown in the results of informational analysis of tasks (Table 7), the finding of linear relationship between RT and amount of information (Table 3), and the result of two-dimensional stimulus-response task shown in (Table 9), clearly indicate the single channel system of decision processing. These results allow us to draw a conclusion that the decrease of performance in prolonged work period is not the outcome of lowering of mental capacity, but the result of changes in the mode of central nervous system. This may be the basis what psychologists describe as "attitude" or "motivation".
