Vitality is changing all day. In the active time zone and the relaxing time zone the Vitality value is different. Since everyone changes the state of the mind depending on the speaker and the timing of speaking please continue to recording until the value of Mental Activity value stabilizes without feeling joy and sorrow as Vitality value rise and fall.
By the way Although it has nothing to do with the characteristics of Vitality the calculation result may change in environments with large background noises. Spontaneous Speech Recording Analysis Fixed Speech Recording Analysis page for the magnitude of the sound being input to the microphone so please check if there is a big noise.