Attention and learning are two of the most important topics in contemporary cognitive psychology and behavioural neuroscience. Of even more interest is how the two interact. Meaningful stimuli and their meaningful effects are invariably embedded in a complex background of meaningless information. Yet, in order to learn about meaningful relationships between events, an organism needs to be able to extract the relevant from the irrelevant. The ability to direct attention selectively to some stimuli and away from others is one fundamental mechanism by which this filtering of information can...