Smartphones are enormously valuable for helping people to fit work activity into times and places outside of the office. Now that workers are able to access email and websites at any time from almost any location, they can be responsive to professional demands in ways unimaginable just a few decades ago. Customer-centric organizations can remain attentive to customers’ needs around the clock. Time-critical events can be addressed quickly. People can leave their offices without fear of being disconnected from their work. Indeed, many would consider smartphones to be among the most important tools ever invented when it comes to increasing the productivity of knowledge work.
However, our new research indicates the greater connectivity comes at a cost: using a smartphone to cram more work into a given evening results in less work done the next day. The reason for this, as we’ll explain, is that smartphones are bad for sleep, and sleep is very important to effectiveness as an employee.
That a well-rested employee is a better employee is well established by research. To note just a few recent studies, insufficient sleep has been linked to more unethical behavior at work, cyberloafing, and work injuries, and less organizational citizenship behavior.
Unfortunately, smartphones are almost perfectly designed to disrupt sleep. Because they keep us mentally engaged with work late into the evening, they make it harder to psychologically detach from the most pressing cares of the day so that we can relax and fall asleep. More generally they encourage poor sleep hygiene, a set of behaviors that make it harder to both fall asleep and stay asleep. Perhaps the most difficult aspect of smartphones to avoid is that they expose us to light, including blue light. Even small amounts of blue light inhibit the sleep-promoting chemical melatonin, meaning that the displays of smartphones are capable of producing this effect.
Thus, as researchers, we had good reason to suspect that using smartphones at night would yield negative effects at work the next day. Specifically, we hypothesized that a greater number of minutes spent using smartphones after 9pm would more negatively affect sleep; that this in turn would leave people feeling tired in the morning; and that, as a result, they would be less engaged at work the next day. In other words, using smartphones to squeeze in a bit more work at night would lead to lower engagement at work the next day at work, through lost sleep as a causal mechanism. To test that hypothesis, we conducted a pair of studies. (These studies will be published in detail in the research journal Organizational Behavior and Human Decision Processes later this year.)
In our first study, we had 82 mid- to high-level managers complete multiple surveys per day for two weeks. This entailed “within persons” analysis, meaning we compared each individual’s daily data only to that person’s own data on other days. This allowed us to examine daily effects, unclouded by individual differences. Consistent with our hypotheses, we found that late-night smartphone usage cut into sleep and made people tired in the morning, and that, as a result, they were less engaged at work the next day.
In our second study, we had 161 employees from a broad variety of occupations (both managers and non-managers) complete the same set of surveys, with the addition of measures of late-night usage of television, laptop computers, and tablets. The harmful effects of smartphones on sleep and work engagement held even after accounting for these other electronic devices. Indeed, out of all those devices, smartphones were associated with the most powerful effects.
Our study adds to a pile of scientific evidence that managers must begin to acknowledge in their work. There are downsides to having employees use smartphones – direct ones for the employees, and less direct but still troubling ones for workplaces. Smart managers will look for creative ways to minimize the problems without giving up the mutual benefits of smartphones.
One solution suggested by Harvard Professor Leslie Perlow, based on her research on high-end consultants, is to have predictable time off. And the best way to start is by agreeing that evenings and normal sleeping hours are the most important times for people to be predictably “off.” This will allow employees to psychologically disengage from work and minimize exposure to the blue light produced by electronic display screens.
Another potential solution calls for creating new norms as to when employees are expected to respond to work email and when they are not. Leaders should be sensitive to how their personal behaviors shape norms; employees will not feel pressure to check their mail late in the evening if their bosses aren’t using that time to send messages. A handy tool is to set a delivery delay on email such that it arrives the next morning. With this approach, managers who are traveling or working odd hours can still communicate at their convenience, but minimize the negative effects on others.
As smartphones become more embedded in our daily lives, we should continue to seek solutions that will enable us to stay in touch with smartphones and still get the sleep we need to be effective the next day. In contrast to a short-term perspective that puts the current work item as the top priority, a perspective that focuses on longer-term performance will leave more room for managing smartphones in a manner that preserves sleep. The more important the job, the more important it is to work with a fresh brain. We would do well to remember that, and not let our phones call the shots.