With its centrality to psychoanalytic thought, excretion was once essential to the understanding of human motivation and personality. No longer, writes Professor Nick Haslam, author of Psychology in the Bathroom. Perhaps embarrassed by fanciful past theories, excretion is all but ignored by modern psychology. Psychology journals on eating disorders abound, Haslam writes, but there is not a single title devoted to the terminal end of the digestive system.

Haslam aims to redress this balance, and presents an unembarrassed survey of the psychology of excretion: flatulence, diarrhoea, constipation, urinary incontinence, inhibition and perversion - all are here. The birth of the ‘anal character’ and its re-emergence as obsessive-compulsive personality disorder is also discussed, as are toilet graffiti and swearing.

The tone is academic rather than journalistic, but the book is nevertheless readable and engaging. An examination of irritable bowel syndrome offers insight into the intimacy of mind and viscera. Flatulence is shown to have connections to many forms of psychopathology. The anxious, for instance, may suffer from an excess of flatus because of hyperventilation. Coprophagia might disgust, but Haslam relates that it can reveal disorders as varied as dementia, psychosis and obsessive-compulsive disorder.

Memorable are the book’s numerous lively vignettes. Researchers investigated urinary hesitancy in public conveniences with the aid of a stopwatch, a mirror and ears primed for the sound of urine hitting porcelain. Psychoanalysts put the concept of the anal character to such extensive use that even seemingly benign children’s stories received their attention. It is Goldilock’s bottom, after all, which breaks the bear’s chair. Toilet graffiti may be in decline as this discourse has now moved online.

I do recommend this book to psychiatrists everywhere, but I also wonder whom Haslam primarily has in mind as a reader. I doubt he has the popular science market in his sights as this book assumes a fair amount of prior knowledge on the part of the reader and is priced for academia. Yet can a book that devotes an entire chapter to toilet seat behaviour (‘Up or down?’ - the answer is actually quite complicated) lay claim to being entirely serious?