Cole Moreton: Forgetfulness is what keeps fathers going, too

She stands in the doorway and yells. The new mum, clutching her baby tight. Clearly knackered, she has lost her car keys, forgotten where she is going, and even forgotten the name of that useless bloke she is screaming at. The father. "Hey... you! Where are they? Why haven't you done that thing I asked? What was it?"

There is, new dads can now reflect wearily, a scientific reason for all this. Mumnesia, a phenomenon as old as Eve, analysed and validated by the University of Boston and the Massachusetts Institute of Technology.

Women suffer memory lapses after childbirth, the scientists say, because they instinctively focus on their baby above all else; their oestrogen levels plummet; and they get shattered, losing up to 700 hours of sleep in the first year. But men have instinctive reactions to new babies, too: we panic, and lager levels rise.

Most of us share the sleep deprivation to some extent, according to the scientists (who say our testosterone levels fall while oestrogen goes up). I have a friend who rises at 5.30am to feed his young twins, gets a train to work, does a high-pressure job and is usually up until midnight helping with the babies. Then he does it all again. He still doesn't feel as if he's doing enough. But even if you "just" go out to work and do little else, new fatherhood can be alarming and exhausting.

If women get mumnesia, then let's call what men get daddy-mindedness. You place the bottle on the work surface, spoon in the milk powder to make a warming, nourishing liquid, and seal the top. Then you carefully unscrew it again and pour the contents of the bottle down the sink.

Or you take a lick of the chocolate left on your fingers from pudding, blow your nose on the nearest hankie, then remember you were in the middle of changing a terry nappy. And no, that wasn't chocolate.

There is always a fellow victim at the park: the guy with the messed-up hair and the werewolf eyes, rocking a buggy back and forth. He doesn't know who he is, or where he is. His mind isn't totally blank, though. This isn't mumnesia, it is daddy-mindedness: he is unconsciously listing the names of every player in the West Ham team of 1988, the year he first went to football with his dad. Parkes, Potts, Dicks, Gale... the baby's cry registers only as the roar of an imaginary crowd.

Let's be clear, daddy-mindedness is not the same as man-nesia. That can strike at any time, whether you are a father or not. Mannesia is forgetting the pint of milk you went out for in the first place and bringing back only a half-eaten packet of bacon Frazzles and a copy of Four Four Two. Mannesia mysteriously misplaces the three hours in the pub between nine o'clock – when you said you would be in, to help with the night feed – and midnight, when you get there.

Daddy-mindedness may actually be worth celebrating. The scientists say mumnesia is part of a woman's self-defence mechanism, helping her forget the pain of having a baby. Daddy-mindedness does a similar job, wiping out the memory of the devastating destruction of mystery and allure that takes place when you see the woman you love on her back with her legs in the air, during the sheer bloody mess that is childbirth.

If this Alien-like scene came to mind every time there was candlelight and oysters (or more realistically, a DVD and a Chinese) there would be no hope of brothers or sisters for the little one. Thankfully, it all gets forgotten. One flirty word, and more pressing matters arise. Three cheers, then, for daddy-mindedness and mumnesia. Without them, none of us would be here. Hip, hip... where were we?