Cochlear implant users perceive mainly sound amplitude modulation cues. Processing of these amplitude modulations can be subject to interferences, so that the perception of a modulation in a target sound can be impaired by a superimposed sound if this sound contains a similar modulation. Such phenomenon, which is observed both in subjects with normal-hearing and in cochlear-implant users, could be explained by difficulties to direct attention to relevant information in complex sound signals. Selective auditory attention also plays a crucial role in speech comprehension in cocktail-party situations where the speech of multiple talkers get mixed at the ear of a listener. Cochlear implant users typically struggle in these cocktail-party situations and report intense listening effort. The present clinical trial aims at evaluating the contribution of selective auditory attention for sound modulations to the listening effort of patients with cochlear implants and of healthy volunteers with normal-hearing during speech perception under cocktail-party-like conditions. Selective auditory attention abilities of patients and controls will be assessed using a psychoacoustical test whereby their ability to detect a target sound amplitude modulation will be measured both in the absence and in the presence of an interfering (i.e. distracting) amplitude modulation occurring in a distant spectral region from that of the target. The effect of this distractor's presence on modulation detection performance will serve as a behavioural index of the subject's auditory attention capacities. The attentional capacity index will then be tested as a predicting factor for the listening effort of the subject during a speech-in-noise consonant identification task. Listening effort will be measured from the pupil dilation response to the presented speech units (pseudowords). This study will enhance our understanding of cochlear implant user's perception and listening effort and will serve as a basis for prognostic tests of listening effort and of implantation success for cochlear implant candidates, based on a simple measurement of auditory attentional abilities.