The subject appears calm. Her earlier burst of energy now forgotten, she moves among her vast collection, thumbing its contents one by one, in the manner of someone scrying a goat’s innards. The nature of her system eludes us, but any questions we have are irrelevant. She trusts it, and that’s all that matters.

At some point in every child’s life, a developmental shift occurs. I refer not to the wonders of speech or motion, nor the slow dawning realisations of empathy or mirroring. I mean that period – in my daughter’s case, now, shortly before her second birthday – when they become a tiny little weirdo sorting every single object in your house.

It does have a cause, it seems. Sorting is just one way a child’s brain begins to assert meaning on the world around them, as they experiment with pattern recognition and object awareness. As recently as a month ago, she considered her toys and books discrete units of fascination. Now, each is a part in some wider system of comparative taxonomy, the contours and meaning of which are known only to her. It’s fascinating to watch, and extremely entertaining.

Sorting is just one way a child’s brain begins to assert meaning on the world, as they experiment with object awareness

She arranges my wife’s lipsticks and mascaras in mandala-like patterns in the bathroom. Loo roll tubes, bottle lids and coins, on the other hand, we now find deposited throughout the rest of our home. This necessitates a Bear Grylls-esque discipline of picking up and shaking out any shoes before we wear them.

In the kitchen, she removes from cupboards items as varied as olive oil, baby formula and, on one occasion, purple willy straws my wife purchased for a hen do – and arranges them in stacks in the manner of a movie detective gibbering at a big wall of clues all tied with red string.

It’s only when we venture out that things get tricky. Last Saturday, a pleasant evening at my sister Maeve’s ended abruptly when our little archivist found three tins of sardines in a kitchen cupboard. She reacted like she’d discovered the Ark of the Covenant. Despite never having seen a sardine in her life, she decided that these were the most precious items she’d ever owned. Within seconds she had them clutched to her breast, and refused to part with them as she headed for the door.

She offered none of her usual resistance when I placed her into the buggy for the trip back, content that a sitting position would better enable her to jealously guard these stolen goods. Once home, she raced into the sitting room and placed the tins in a stack of three, beside a commemorative King Charles coin I bought my wife for her birthday.

Her delight at this moment is near impossible to describe, but I can only hope I’ll ever know such joy. I do not know the arcane workings of her system, but I trust it now. Sardines were the answer. The question does not matter.

Did Ye Hear Mammy Died? by Séamas O’Reilly is out now (Little, Brown, £16.99). Buy a copy from guardianbookshop at £14.78

Follow Séamas on X @shockproofbeats