The determination system includes a presented-speech sound control section for determining a speech sound to be presented to a user auditory/visual stimulation presentation sections for presenting the determined speech sound as an audio/a character a group-wise summation section for taking a summation of an event-related potential of an electroencephalogram signal of the user for each group of speech sounds a first determination section for, from the event-related potential having been subjected to summation for each group, making a group-by-group determination of comfortableness as to whether the user is comfortably hearing to the speech sound, to at least determine whether the user is listening to the speech sound with strife, or to determine whether the user is annoyed by the speech sound and a second determination section for, from the event-related potential, making a speech sound-by-speech sound determination of intelligibility as to whether the user is clearly hearing the speech sound.
