In recent years, the links between neural activity and perception have been an area of interest in cognitive neuroscience. Combined psychophysiological and psychophysical experiments provide a new powerful tool for establishing the relationship between neural activity and perceptual performance. In animals, intracellular recordings combined with psychophysical detection indices have revealed that a particular neuron or set of neurons can play a critical role in the generation of a perceptual event, showing detection functions (referred to as neurometric functions) which are remarkably similar to psychophysical detection functions, or psychometric functions (Parker & Newsome, (1998) Annu. Rev. Neurosci., 21, 227–277). As noninvasive techniques for recording neural activity are now available, studies combining neuroelectric and psychophysical measures in humans are sparse. In the present study, the accuracy of the human brain in detecting differences in sound duration and the subject's ability to perceive the same differences were tested by means of mismatch negativity (MMN) and the distance between the distributions of false alarms and hits (sensitivity index d′), respectively. It was found that the accuracy of the human auditory system to represent sound duration information is related to the duration context in which the sounds are heard, and that these contextual representations determine the accuracy of perception at the behavioural level.