A method of controlling stimuli applied to an animal or human subject, in which use is made of pupillometer including a generator unit for generating electrical stimuli, the method comprising the following operations: • keeping two electrodes for applying electrical stimuli in contact with the skin of the subject; • connecting the electrodes to the pupillometer including a measurement unit arranged to measure at least one size or shape characteristic of the pupil of an eye of the subject, and including an impedance-measuring module and a calculation unit; • using the impedance-measuring module to measure the impedance between the two electrodes in order to verify that they are correctly positioned, by comparing the measured impedance with a determined impedance value; • using the electrodes to apply to the subject successive electrical stimuli as delivered by the generator unit, the stimuli being of intensity that increases between an initial value and a final value, which values are stored in a memory of the pupillometer; • using the measurement unit in repeated manner while applying the electrical stimuli in order to measure at least one size or shape characteristic of the pupil of an eye of the subject; and • when the calculation unit detects a significant variation in the measured characteristics of the pupil, storing data corresponding to at least one stimulus applied to the subject, and decreasing or stopping application of the stimuli; and wherein, in order to detect a significant variation of the measured characteristic of the pupil, the variation of the measured characteristic is compared with a predetermined value for variation of this characteristic, which value is stored in a memory of the pupillometer. • keeping two electrodes for applying electrical stimuli in contact with the skin of the subject; • connecting the electrodes to the pupillometer including a measurement unit arranged to measure at least one size or shape characteristic of the pupil of an eye of the subject, and including an impedance-measuring module and a calculation unit; • using the impedance-measuring module to measure the impedance between the two electrodes in order to verify that they are correctly positioned, by comparing the measured impedance with a determined impedance value; • using the electrodes to apply to the subject successive electrical stimuli as delivered by the generator unit, the stimuli being of intensity that increases between an initial value and a final value, which values are stored in a memory of the pupillometer; • using the measurement unit in repeated manner while applying the electrical stimuli in order to measure at least one size or shape characteristic of the pupil of an eye of the subject; and • when the calculation unit detects a significant variation in the measured characteristics of the pupil, storing data corresponding to at least one stimulus applied to the subject, and decreasing or stopping application of the stimuli; and wherein, in order to detect a significant variation of the measured characteristic of the pupil, the variation of the measured characteristic is compared with a predetermined value for variation of this characteristic, which value is stored in a memory of the pupillometer.