But the tyranny of email requests is a relatively recent phenomenon. Those who remember the early days of the consumer internet probably recall the cringe-inducing dial-up modem sound. The year was 1995, and the cost of internet access was still calculated on a by-the-minute basis, like a long-distance phone call. I would log on and off dozens of times a day in anticipation of surprise greetings from a distant friend or a remote relative. Mom dubbed me “the lab rat,” as if I were some poor animal with an electrode hooked to the area of my brain associated with cravings, waiting to receive stimulation. In a laboratory, such mice were shown to forgo food and water as they incessantly pushed a lever that administered shocks of pleasure to them until they died of exhaustion. Though I never once missed dinner, AOL’s “You’ve Got Mail” announcement was enough to perk me up with adrenaline-fuelled excitement.

Like all other things, email communication is subject to the law of diminishing returns. Today’s email avalanche and the pressure to reply instantly only elevates work-related stress, with its chronic effects manifesting in a range of physical conditions, from heart disease to sleep problems, from headaches to memory impairment. But health concerns aside, does the constant streaming of work emails help boost productivity? Is Google a top firm because of Schmidt’s approach or despite it? Harvard Business School professor Leslie Perlow decided to run an experiment.

Hardly a techie herself, Perlow was trained as an anthropologist and spent most of her time trying to understand human behaviour through first-hand observation. But she somehow managed to convince the executives at Boston Consulting Group to encourage members of a team to completely disconnect one day of the workweek. No emails, no phone calls. At first, the consultants were concerned about their performance evaluations and what they owed the clients and their colleagues. But as the weeks wore on, fear subsided. Five months later, people who took time off reported “higher job satisfaction, more open communication, increased learning and development,” and most importantly, “better products delivered to the client”.

That final observation was peculiar. Why would staying disconnected yield higher-quality output? Neuroscience offers us some clues. It’s not so much about the content of the information we receive but the way it’s delivered and processed by our brains.

Most of us harbour the desire to be a superhuman manager, capable of doing many things at once with high success: juggling phone calls, emails, live conversations, and text messages, all at the same time. In reality, no human can truly multi-task. Neuroscientists have shown that our brain simply switches from one task to another. Because separate projects are processed in separate parts of the brain, they require separate start times and separate monitoring processes. That explains why an interruption, even if short, delays the total time required to complete a task by a signification fraction. And the constant toggling incurs a major switching cost. After an hour or two of attempting to multi-task, we are often so tired that we can no longer focus. It’s because those very neural chemicals we needed to focus are now gone. In fact, the mere awareness of an unread email sitting in your inbox can effectively reduce your IQ by 10 points.

That’s when we see that some companies are trying new tactics to save their employees from major “brain drain.” Employees from Daimler, the German car maker of Mercedes-Benz, can opt for a “mail on holiday” option, where all incoming emails are automatically deleted. “With ‘mail on holiday’ they start back after the holidays with a clean desk. There is no traffic jam in their inbox. That is an emotional relief,” said Wilfried Porth, board member for human resources. The French government went further: a new law requires companies with more than 50 employees to establish hours for staff to not send or answer emails.

But these are hardly European styles of indulgence. The biggest problem of multitasking is that it disrupts the kind of sustained thought usually necessary for problem-solving and creativity. In the age of ubiquitous connectivity, if we only relay messages from point A to point B without creating anything new, the value we add is indeed low. We are then no more than human routers.

Howard Yu is professor of strategy and innovation at International Institute for Management Development. In 2015, Yu was featured in Poets & Quants as the World’s Best 40 Under 40 Business School Professors