Perception is not a passive process. Instead, the brain uses an internal model about the world to create predictions about future sensory events. In case that sensory input deviates from the predictions of this hierarchical generative model, a prediction error is generated to update the model. In the course, we will discuss basic mechanisms of the predictive processing account, and examine the empirical evidence for its claims in different domains of perception and action. We will discuss behavioural and brain data, with a special focus on the mismatch negativity, which is considered as the EEG/MEG-correlate of the prediction error signal. Finally, we will discuss theories that propose aberrant predictive processing as an underlying mechanism in clinical conditions like autism spectrum conditions and schizophrenia, which have gained substantial support over the last years.