Higher productivity, improved wellbeing, gender equality, and even lower commuting carbon footprints – we’ve all seen the headlines giving a 4-day working week a glowing review.

With the results from ESRC Digit supported research into the largest coordinated UK-wide trial just in, and showing that 92% of the employers have chosen to continue a 4-day week post-trial, it seems the evidence is steadily stacking up in favour of reducing time at work with no loss of salary.

But exactly why is a 4-day week effective at enhancing staff wellbeing, and performance in the workplace?

Psychological and physiological changes

In the Sussex 4-day Week Study, we set out to take a deep dive into the psychological and physiological changes that take place when employees switch to a 4-day week. By examining what changes in mind, brain, and body, we hope to reveal the mechanisms by which a 4-day week can have beneficial effects on employees (and thereby ultimately on the employer, too).

We’ve been working with 10 local businesses in the Brighton and Sussex area who were seeking to trial a 4-day week. Before they made the switch, we first gathered lots of baseline data, on employees’ mental health, lifestyle, and workplace performance. For the first time in any 4-day week trial, we also took MRI scans to look at brain function; blood tests to look at physical health and immunity; and sleep watches to measure sleeping patterns.

Staff then switched to a 4-day week, and we monitored what changed over a 12-week period. At the end of the 12 weeks, we then repeat the MRI brain scans, blood tests, and sleep assessments.

Some of our employers’ trials are still underway, and we aim to continue enrolling more. This means that we don’t yet have the final results on the physiological changes that are taking place.

However, we can already see in our questionnaires that our findings are mirroring those of the national trial: improved mood, reduced burnout, and higher (self-reported) productivity.

The next step (once we’ve recruited more firms) is to assess what brain changes might be underpinning those improvements.

How lifestyle shifts may affect productivity

When employees take part in our MRI scans, we ask them to undertake a number of tasks while we measure brain activity (using functional MRI, or fMRI, for short). One of these tasks measures function of the prefrontal cortex, a large part of the brain just behind the forehead that we know is important for attention, planning, and inhibitory control (see Figure 1). The second fMRI task is measuring function of the insular cortex, which underpins our ability to sense what our body is feeling, such as a fast heartbeat, or shallow breathing.

Figure 1: The prefrontal cortex (green) and insular cortex (blue), which enable us to plan our work, and process bodily stress signals, respectively.

We think that these different aspects of brain function may be underpinning different benefits of the 4-day week. In particular, we think that improved prefrontal cortex function might be particularly linked to productivity, because the functions of this brain area enable us to plan our work, stay on track, and not get distracted by off-task activities, such as checking emails. In addition, we think that changes in insular cortex function might be particularly linked to mental health, because this area of the brain enables us to process bodily stress signals.

We already know from other lines of research that the effectiveness of these different brain areas can change when people experience lifestyle shifts.

For example, the prefrontal cortex is very sensitive to sleep deprivation. We suspect that when employees switch to a 4-day week, sleep improves – both because they have slightly more time in bed on their day off, but also potentially because they experience better quality sleep during the rest of the week too (through being less worried about work).

There is a potential role for changes in the use of digital work tools, too. We know that exposure to the blue light of devices late at night can send the wrong message to the brain’s sleep circuitry to stay awake. This happens because blue light exposure suppresses the ‘sleep hormone’ melatonin. We also know that digital communication tools often hijack our visual and auditory attention, to the expense of the brain areas that are needed for focus and ‘deep time’. A common modification that 4-day week knowledge economy employers are making to working practices is therefore to encourage staff to switch off digital communication tools for some periods of the day. If employees working a 4-day week spend less time engaged in digital work, especially later in the day, this may exert another beneficial effect on sleep.

The questionnaire results from the national trial certainly suggest that sleep does improve on a 4-day week, and we hope our sleep watches will help confirm it. If so, it may be that we are then able to identify the specific mechanism behind better productivity in the workplace – because that extra time off boosts sleep, which in turn improves prefrontal cortex function, and this in turn improves performance at work.

In order to find out, we are continuing to enrol local employers to our study. Since MRI scans can’t be done online, we have been focusing on organisations based in the South-East of England. This means their employees can travel to the University of Sussex campus, where our MRI facilities are. Participants who’ve taken part so far say that it’s a novel experience to have an MRI scan as part of a 4-day week trial, and enjoy seeing what their brain looks like afterwards!

As the evidence base surrounding the 4-day week grows, we are excited to be part of the international community helping organisations to implement a 4-day week, and to understand not only the benefits it can have on their business, but also, crucially – why.