The pupil and stimulus probability.
D000161:Acoustic Stimulation; D000293:Adolescent; D000328:Adult; D001307:Auditory Perception / Q000502:physiology; D001341:Autonomic Nervous System / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D011336:Probability; D011680:Pupil / Q000502:physiology*