The connection between the affective state of amusement and increased physiological arousal is used to analyse the ways in which a text can encourage a receiver’s appreciation of recognised humour. Drawing on the ideas of a mutual cognitive environment from Relevance Theory and Common Ground from Text World Theory, it is argued that humour appreciation is encouraged when recognition of humour requires an optimal amount of processing effort from a receiver. This is illustrated by examining recognisably humorous stereotypes and metaphors to explain why some are found more amusing than others. Literary works considered include: Three Men in a Boat by Jerome K. Jerome, Excellent Women by Barbara Pym and Nutshell by Ian McEwan.