Two fundamental principles dominate the signal processing of the auditory system: selectivity and adaptation. The response of the auditory system is selective for various acoustic features and the representation of these acoustic features adapts over time. This thesis is concerned with the characterisation of selectivity and adaptation in the human auditory system. Initially, selectivity for modulation rate and adaptation to intensity are characterised in a central auditory model. Next, selectivity for temporalmodulation rate and selective adaptation to both intensity and temporal modulation rate are characterised in psychophysical data.