[Surprise me!--humour as a biological phenomenon II].

What makes us laugh differs from one person to the next. Nonetheless, it is possible to formulate some features common to all types of humour. One of these is the experience of something surprising or new. Although an overall theory of humour is still lacking, several recent cognitive theories of humour have hinted that humour should be understood in the setting of a general biological need to learn to navigate and act in an ever-changing cognitive environment, by discovering and recognizing repeated patterns in novel experiences. In this, the second and last of two papers on humour in a biological context, we examine the cognitive theories of humour.