"C'mon, crawl," I urge. As if to humour me Jemima kicks her legs for a few seconds, breast-stroke fashion, before giving up and lying her head on the carpet and sticking her thumb in her mouth.
I take our training to the next level, lifting myself up onto my hands and knees and crawling excitedly around her. She's not really looking, and so I feel a little bit stupid.
Two minutes later, Jemima isn't the only one who has given up, and I've taken the opportunity to have a little father-daughter cuddle instead.
I don't know why my wife and I are so keen for Jemima to start crawling; experience would suggest that as soon as she does we'll be wishing she couldn't, especially when she starts crawling towards the fireplace or disappearing from the room when our backs are turned. But still, we are keen. Really keen.
I say I don't know why: I do. It's because other parents we know who have children of a similar age just love to boast about how little Timmy has been crawling for ages. I have a colleague opposite me at work whose son is a month younger than Jemima, yet has already mastered the art of pulling himself up onto his feet. As he tells me about how well his son is doing, my mind wanders back to the image of Jemima gently drooling onto the floor as she sucks her thumb and drifts off to sleep.
We shouldn't be so worked up about it. Far too often these days we gauge the progress of a child by these milestones, which actually don't matter one bit. They should be crawling by this age. They should be walking by this age. It's all a load of rubbish.
It's not like Jemima is never going to learn how to crawl: plus, it's not even an important skill to have. When was the last time you saw an adult crawling down the street (apart from in Cardiff city centre on a Friday night)?
I've come to the conclusion that it's not that Jemima is lazy; it's that she isn't wasting time and energy on a redundant form of transport, and suddenly one day she'll just get up and start walking. Turns out I've spawned a genius.
There's no getting away from it, though. Despite these progress milestones being utterly useless, we as parents still can't help but mark our children by them, and as such we inevitably compare our children to other people's kids, as if growing up is suddenly some kind of competition.
It gets us down on occasion, perhaps even making us feel inadequate; and it is at times like this when we should remind ourselves just how pointless milestones are. Let kids be kids, and progress at their own pace. They've got a whole life ahead of them full of pressures and strain, so let's ease off them a bit.
So, I suppose it doesn't really matter that Jemima can't crawl yet. We should only start worrying when she reaches the age of five or six and she's still dribbling into the carpet, I guess.
And next time a smug parent sidles up to me and boasts that their child can walk already, I think I'll just turn to them and say "So what?". That ought to work.