He’s found a secret tunnel and hasn’t told a soul.

It’s barely two feet tall and tucked out of sight, leading to a hidden room he can just about reach if he crawls in on his hands and knees. He spends the next few weeks working on it, adding everything from fairy lights to lava lamps, not to mention a strictly confidential handshake and password that changes daily.

It isn’t long before word gets out.

Soon enough the walls of this makeshift den are covered in signatures from people who’ve crawled in after him, among them the CEO of Disney, Billy Crystal and Steve Jobs.

Welcome to Pixar, which is in the middle of a run nobody in Hollywood has ever matched: fourteen films in a row, each and every one of them smashing its way to number one at the box office.

Funny Business

We tend to think of fun as a luxury for the companies that’ve made it – office slides and ice cream bars are a flashy indulgence for the tech giants so far ahead they don’t need to worry about being taken seriously anymore. First comes the success, then comes the freedom to enjoy it.

Biology suggests we may have got the order the wrong way round.

For generations, we’ve built offices and entire careers around the idea that the most important people keep a straight face – the higher up you go, the more serious you’re expected to be. Fun happens after the important stuff – laughter belongs in the pub, silliness is for the Christmas party, and anyone enjoying themselves a bit too much on a Tuesday afternoon probably needs reining in or a quiet chat with HR.

We’re taught early on that fun and work belong in different boxes: play is the prize, not part of the process.

Being a bit miserable at work seems to be proof that something productive is happening.

More often than not, it’s just evidence of being a bit miserable.

Deadly Serious

Evolution has spent millions of years stripping away anything that doesn’t earn its keep; any trait without a clear and useful job will find itself chucked in the bin without so much as a thank-you.

Laughter has been making the cut for longer than language has.

Playfulness is one of the oldest circuits we know of: it’s buried deep in the same ancient wiring as fear and rage. It’s so firmly embedded in the factory settings of life that a rat raised completely alone, having never once seen another rat play, will still pounce, wrestle and pin the first playmate it ever meets.

Nobody has to teach it.

But the circuit comes with a painfully sensitive off switch – if you drop a tuft of cat hair in the cage play will stop immediately – not for the afternoon, but for days at a time.

When the brain picks up a threat, the amygdala floods the system with stress hormones and something unexpected happens. The prefrontal cortex, the part of our grey matter that does fresh and complex thinking, temporarily goes offline.

In other words, the brain handles stress by switching off the part that does the fancy stuff.

Original thinking involves making connections between things that don’t obviously belong together – it requires a brain relaxed enough to go off-piste and try something weird without worrying too much about how it’ll land.

That’s a big ask in a room having about as much fun as a fire drill.