Asking the father of a newborn to comment on a book called Dad Brain is a bit like getting an alcoholic to write a review of The Lost Weekend, or a madman to dictate a critique of American Psycho from the confines of his straitjacket. If the title’s implication is true, I thought, my IQ may have taken a hit since my daughter Isobel arrived late last year. Might I be incapable of reviewing anything, let alone a book about my incapability?

Yet when Literary Review sent me this accessible account of the latest science on fatherhood, I wearily donned my sling, crammed the weeping Isobel into her marsupial pouch and got reading. And to my relief, I learned that I probably shouldn’t worry. I say ‘probably’ because there isn’t all that much scientific data about fatherhood. That is the USP of this book ­as well as its weakness. Darby Saxbe, a professor of psychology at the University of Southern California, was involved with one of the few studies of the changes that fatherhood produces in male brain structure; it revealed that men’s brains get 1 per cent smaller. Whereas mothers’ brains shrink in several places, fathers lose capacity exclusively in the cortex, the area that enables humans to think ahead. How does this work? Is 1 per cent a lot to lose or a little? I’m not clear on the answers to these questions even now.

While reading this book, I was repeatedly vomited on by my daughter, and I reflected that we were each, in our own way, producing reviews. As I mopped at my thigh with sodden kitchen paper, I realised that my approach to this task was that of a Method actor, viscerally