Earlier this month, a debate raged on X over hustle culture.

The first shot came from a founder who sleeps on a mattress in his office. In barely two years, he's built his startup to a $2.6 billion valuation.

Accomplishing this involved seven-day working weeks, a café inside the office (because nothing nearby stayed open around the clock), and a team so bought-in that around 60% of his earliest employees have the company logo tattooed on their bodies. His worldview fits on a bumper sticker: if you're not working seven days a week, you're going to lose.

Then a second founder returned fire. He's built a $1.25 billion company of his own, and a profitable one, running it just five days a week.

He stops every evening to cook dinner for his family, and treats it as a point of pride that the company doesn't need more from him than that. “Real mastery,” he wrote, “is achieving the outcome with the least necessary effort.”

The internet internetted and picked sides. But the fight is largely about numbers: does success demand five days or seven? Forty hours or ninety? A new study published last month in Science Advances can't tell you what that number should be. What it can do is suggest the number was never the interesting variable in the first place.

P.s. More action awaits you in our archives, including what a 60-year study of winners reveals about reaching the top, the personality trait shared by 1381 millionaires, and why when you're launching something new, you need social dandelions.

The relationship nobody was arguing about

If both companies are succeeding while running at completely different intensities, then could it be that there are other, more important forces at work? The science says yes, and the researchers behind our new study caught one such force inside a brain scanner.

It comes down to how one variable—the kind of environment you work in—affects another: a neurological process that sits underneath every great idea ever made. Both founders depend on this process, and so do you, every time you do something creative. And it's what the researchers set out to put under pressure.

It was led by Lars Schwabe of the University of Hamburg and Alison Preston of UT Austin, two of the world's leading authorities on how the brain turns experience into knowledge.

They began by bringing 121 healthy volunteers into Schwabe's lab.

On day one, they showed participants a number of picture pairs. Every pair was a face or a place beside an animal—say, a particular man with a llama, or a particular beach with a parrot—and the only job was to remember the two belonged together. They went through a cycle four times—shown twenty-four picture pairs, then tested on them—until the links were solid.

Day two is where it forked. Half the group was subjected to what can only be described as psychological warfare. It started with a mock job interview before a stony-faced panel in lab coats. A camera filmed each participant, and a screen behind the panel fed their own image back at them—so they had to watch themselves. Then they counted backwards from 2,043 in steps of seventeen while the panel stayed cold. It's a gold-standard exercise for inducing stress.

The other group were given a more gentle experience. They gave a speech about a topic of their choice and performed a simpler mental arithmetic task. No judgmental panel, and no camera.

It was far less stressful, as evidenced by their biomarkers. The stressed group's heart rate, blood pressure, and cortisol all spiked. The control group's cortisol simply fell over the morning, in step with our natural daily hormone cycle—undisturbed by their calmer session.

Then, with no time to recover, both groups learned a new set of twenty-four picture pairs. Each one included an animal from the day before, now paired with a different picture: an object. For example, the llama that appeared with the man on day one now showed up beside a wristwatch.

Now for the moment everything had been leading to, though the participants had no idea it was coming.

They were shown one of the objects they'd just memorized. Say, the wristwatch that had been sitting beside the llama. Then three faces appeared, with a simple question: who owns the wristwatch?

All three faces were familiar. Each had turned up the day before, every one paired with its own animal. But only one of them connected to the watch. Yesterday, the man had gone with the llama. Today, the llama had gone with the wristwatch. So the watch was the man's—even though the two had never once been shown together.

That was the whole game. Not whether you could remember the pairs, but whether you could span the gap. Follow the llama from the watch back to a face you were never told the watch had anything to do with.

The everyday version is a friend who shows you their new pale-blue scooter. A week later you spot that same scooter parked outside the library. You infer, without being told, that your friend is probably inside. Two separate memories, silently welded into a conclusion. That welding is a specific job done largely by the hippocampus, and it's the engine underneath analogy, synthesis, and most of what we call insight.

When you scale that humble move up, it becomes the history of breakthroughs.

For example, in 1971 Bill Bowerman had two kinds of running shoe and both were useless on his hard new track. Metal spikes tore it up and plain rubber flats slipped—and nothing in between existed.

Then he looked down at his waffle over breakfast one morning. Most people would just see a waffle. Bowerman saw a sole. If you inverted the waffle grid by sinking the ridges and raising the squares, you'd have a tread of rubber studs that could bite the track without a single spike.

Then another dot connected. He looked over at the waffle iron and realized he didn't just have the shape, he had the machine to make it. He rushed to the garage and poured liquid rubber into the iron. To his wife's displeasure, it was destroyed, but it set him on the path to the Nike Waffle Trainer and the company it built. On the surface, a waffle has nothing to do with a shoe. But the two were connected in Bowerman's mind by the grid and the machine that made it.

We've seen many examples of analogical breakthroughs like this in previous editions, and the brain's ability to make these leaps is what was being pressure-tested by this study.

So how did the group with stress still fresh in their blood do, against the calm one?

The bridge never built

The stressed group, fresh from their nightmare interview, showed altered activity in the brain's memory center—the hippocampus. It's not that stress made them forgetful. They learned the new pairs just as well as everyone else. It's that it made them worse at connecting the dots.

The difference came while they were memorizing the new pairs on day two.

When a calm participant stared at the wristwatch and the llama, the old memory of the man lit back up—their brain subconsciously bubbling the related memory to the surface, holding all three together for an instant. That flare is the bridge being built.

In the stressed group, it stayed dim. The man's signature in the hippocampus barely stirred as the new pair went in, so the bridge was never laid.

And it went further than mere absence. Linking two memories normally stores them in overlapping code and their patterns grow more alike. The stressed hippocampus did the opposite, pushing the man and the wristwatch apart, filing them as if they had nothing to do with each other.

All of this happened while they were memorizing the new pairs—before anyone had asked them to connect dots. By the time that question came an hour later, the stress had passed and their cortisol was back to baseline. The bridge gets built as the information first goes in (the moment Bowerman looked at the waffle), or, there’s a risk it doesn't. Sometimes an insight will take a while to strike you, but it's possible that a calm weekend can't pour a foundation that stress prevented from being laid in the first place.

The effect hit hardest on the images people liked. Participants who found a picture pleasant normally got a boost in their ability to connect it to other memories—good feeling tends to grease the wheels of association. The control group got that boost, but the stressed group got none of it. The lift their favourite images should have given them was wiped away. This suggests that even creative work you genuinely enjoy—the kind you'd normally shine at—may lose its edge when the environment feels like a threat.

The confidence-creativity connection

So back to the two founders trading fire on X. Their grindsets may differ, but neither could have built a billion-dollar company without the dot-welding process at the heart of Schwabe and Preston's study. Every great company—and every great project, for that matter—rests on ideas welded together in a shape the world hasn't quite seen before. This means the number of hours you pour into that work probably matters far less than the level of threat you feel while you're doing it.

And threat is a precise choice of word.

There's another vast, well-replicated literature distinguishing two kinds of pressure.

When we're handed a demanding situation—a job interview, a high-stakes pitch, or a demanding performance—the body typically answers with a cocktail of stress hormones. But the cocktail comes in two flavours. Cortisol is in both, which is why we call both “stress”. We saw that spike in the group sweating through the mock interview.

But because that interview was engineered to make them feel overwhelmed—the stony panel, the camera, the backwards counting from 2,043—they got the “catabolic” version, in which cortisol dominates and drags the body toward inflammation and breakdown. It's the cocktail that saps performance and, over time, health—and, as this study adds, disrupts the brain's ability to connect ideas.

But when we face a demand that we feel equipped to meet, we get a performance-enhancing cocktail instead. Picture the same experiment run another way. Imagine a warm panel nodding you on, with plenty of time to prepare, and a reminder going in that you've handled worse. That makes your body more likely to serve you the “anabolic” stress cocktail—where cortisol is kept in balance, paired with restorative hormones like testosterone, and extra blood and oxygen that sharpen the mind. It brings confidence, focus, resilience, and a bias for action. You get the upside of stress without the damage, and it tends to lift performance above baseline rather than hinder it. Researchers call it the biology of courage, or a “challenge” response.

Put simply, the key factor that determines whether you get the harmful cocktail or the enhancing cocktail is not whether you have what it takes to tackle the challenge in front of you, but whether you feel like you do. The voice inside your head, how others treat you, how well you slept—all of these and many more can influence that feeling.

What if a group in this study had been pushed into a challenge response instead? Might their ability to connect the dots have been sharpened relative to the calm control group, not merely spared? Hopefully someone runs that one soon.

Until then, if I had to put money on which of the two companies to back, I wouldn't bet purely on the hours. I'd be more swayed by which one builds a culture where people feel they've got what it takes to meet whatever's put in front of them—the one that keeps its people in the challenge zone and out of the threat zone. That, the study suggests, is the condition under which the dots actually connect.

So work hard, if hard is what the work demands. Just seek to do so in an environment that feels, even under pressure, like it's there to hand you what you need to rise.

Final Calls To Action

• Want to understand the implications of recent advances in tech, culture, and product design? If so, Scott Belsky's monthly analysis is essential reading. In his latest June edition, Scott explores why even the smartest companies keep underestimating exponential growth, the rise of “efficient AI”, why “talent density” is overtaking headcount as the metric that matters, and more!

• I recently stumbled across a bestselling author and speaker who swears by the Action Method Book to get things done. “If I'm not making something, I'm not happy,” he said. “To me ABC means Always Be Creating.” Turns out he uses Action Books to manage his podcast, newsletter, client work, and a number of special projects. Your ideas deserve the same momentum. Shop the Action Method.

Thanks for subscribing, and sharing anything you’ve learned with your teams and networks (let us know what you think and share ideas: @ActionDigest).