The selection of a passage to excerpt required the exercise of judgement, a benefit summarised by Justus Lipsius, another Dutch scholar, in the Latin tag Non colligo, sed seligo (‘I don’t collect, I select’). Selecting the appropriate common place (or locus, under a headword) for a given excerpt demanded still deeper engagement with its ideas, and

‘The building of the prompt book took hours,’ Coppola recalled, ‘and the tedious activity of cutting, reinforcing and organising the pages provided many meditative hours during which one could use the other side of the brain to roam over the ideas and essential themes of the playwright’s intention.’

As we verbally process trauma, we have to name and label our emotions: and this practice, in turn, is known to improve life satisfaction. It’s known as the A-to-D emotion theory, in which ‘analogue’ emotions (non-verbal, woolly, hard to organise, imprecise) are turned into ‘digital’ (verbal, cognitive, easy-to-organise) chunks. ‘Your writing goes

The correlation, he would later write, was ‘exceptionally powerful’, and unambiguous: ‘when people write about upsetting experiences it has a positive health effect upon them.’

Solso’s experiment, subsequently replicated and refined, changed the way we think about artists at work. It showed that to create a realistic, figurative image, one that ‘looks like’ the subject, you have to do something that doesn’t come naturally, and – if you’re painting a portrait – actively disengage the parts of the brain that instinct tells

there’s no personal information apart from Merer’s name, and the record must have been a report for his masters. This lack of written introspection makes it typical of the ancient world.

He left paintings unfinished for decades – Lisa del Giocondo sat for the Mona Lisa when she was in her early twenties, and was thirty-nine when Leonardo died, still working on it – and he evidently felt similarly about his manuscripts and notebooks.

And they copied not in the formal gothic or antique scripts that took years to master, but the rapid cursive scripts used by merchants and notaries; people who had to write accurately, but also quickly.

We can draw striking conclusions from Tchalenko, Solso and Chamberlain’s experiments. Long practice teaches an artist to direct their gaze in an unusually focused way; it trains them to repurpose areas of their brain; and it changes the very structure of the brain’s neural networks.