Struggling with a difficult mental task? Zapping the brain region linked to our motivation to make a mental effort might help – for a while. People who had this part of their brain stimulated by electrical currents excelled at a difficult task, but also became more mentally fatigued afterwards.

“Their performance is much better; however, this good performance comes with lower motivation in the end,” says at the University of Munich, Germany.

Xia and her colleagues put electrodes on the heads of 31 volunteers with no known health conditions. During a half-hour session in an MRI scanner, the volunteers spent 20 minutes doing the 3-back memory test, where you have to remember and identify the third item back as an ongoing sequence is presented to you – a very demanding mental task. They were then offered €1 for doing an easy test or €2 for a harder one.

During the 3-back memory test, the electrodes delivered transcranial direct current stimulation (tDCS) to a region of the brain called the dorsolateral prefrontal cortex to randomly chosen volunteers, who were unaware they were receiving it.

Other studies have shown the dorsolateral prefrontal cortex is involved in we make. “Our dorsolateral prefrontal cortex helps us to work hard,” says Xia.

The volunteers who had tDCS reacted faster and more accurately than those who didn’t receive this stimulation. For instance, their average reaction time was 0.98 seconds, compared with 1.12 seconds with sham stimulation.

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Xia thinks stimulating the dorsolateral prefrontal cortex will boost brain performance generally. “I can imagine any cognitive task will be better, but afterwards you will feel more fatigued,” she says.

After the tests, the volunteers who got tDCS had higher levels of the neurotransmitter glutamate in their dorsolateral prefrontal cortex, according to a non-invasive technique called magnetic resonance spectroscopy. The higher their glutamate levels, the more likely they were to choose the €1 task over the €2 one.

Some researchers think mental fatigue is a result of the buildup of glutamate, which can harm cells at high levels. Xia thinks her team’s findings are the strongest evidence of this yet. The findings suggest it is important to take a break when you feel mentally tired, she says.

Xia thinks future studies should also look at the dorsolateral prefrontal cortex in people with conditions such as depression, which can affect motivation.

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“I think the claim that the stimulation made people ‘work harder’ is well substantiated,” says neuroscientist Emile Radyte at Samphire Neuroscience, a UK-based company exploring the use of tDCS to treat conditions such as premenstrual syndrome. But the study doesn’t prove that higher glutamate levels were the cause of the greater mental fatigue, she says.

Radyte says her trials have shown that if productivity is hindered by conditions such as premenstrual syndrome, applying tDCS over the dorsolateral prefrontal cortex can restore it. But she isn’t sure about using it to boost mental performance. “A 20-minute laboratory task does not establish a net productivity benefit over a working day,” says Radyte.

It is a good study, says at University College London, but the greater mental fatigue could be a result of using more neural energy, rather than the buildup of glutamate. It’s also hard to precisely target the dorsolateral prefrontal cortex with tDCS without an MRI scanner to guide you, says Lavie. “Drink coffee instead,” she says.

You don’t need a jet plane to get jet lag – even feathers will do. At least one species of bird gets jet lag, in the sense that its body clock can diverge from local time by more than an hour on fast flights across the Atlantic, as revealed by navigational errors.

“We’ve slightly shied away from using the term jet lag itself, because people associate that with the health impacts of that clock shift, rather than the clock shift itself. But it’s exactly the same process that causes jet lag in people,” says at the University of Oxford. “It’s having these physiological and behavioural effects, where the birds are mistiming their behaviours.”

It is likely that other long-distance fliers, possibly including some insects and bats as well as birds, also get jet lag in the clock-shift sense, says Lewin.

Manx shearwaters are small seabirds that fly vast distances, using a technique called to exploit wind gradients near the sea surface. “They’ve evolved this niche of being really amazing long-distance travellers,” says Lewin.

They breed on islands around the UK and Ireland. While parents are raising a chick, they may fly more than 1000 kilometres westwards to reach rich fishing grounds in the mid-Atlantic. Once they have food, they fly back in a fairly straight line, diverting only to skirt around landmasses such as Ireland.

How do they achieve these navigational feats? While some birds can sense Earth’s magnetic field, Manx shearwaters don’t appear to. Lewin’s team has confirmed this by attaching small magnets to the birds that should disrupt geomagnetic navigation. They .

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Instead, it appears that shearwaters rely on a sun compass – if you know what time it is, you can maintain a course by adjusting your orientation relative to the sun. Many animals, from insects and fish to turtles and birds, have been shown to do this. If their internal clocks are reset using artificial light and darkness, they head in the wrong direction.

“We realised that there might be a kind of natural experiment where the birds were manipulating their own clocks,” says Lewin.

For instance, at 6am, a Manx shearwater wanting to fly eastwards back to its nest needs to head sunwards. At noon, it needs to fly at right angles to the sun, which will be due south. But if a shearwater travels 15° of longitude eastwards, the local time will be 1pm, while its internal clock will still register the time as noon, so the sun will no longer be due south. This means birds flying rapidly east should veer slightly off course in a clockwise direction over the course of day, in the absence of other cues.

Other researchers have been attaching GPS trackers to Manx shearwaters for decades, so the paths taken on nearly 4000 foraging trips are known. Sure enough, when Lewin and his colleagues analysed these flight tracks, they found birds on rapid return flights tended to deviate clockwise when out of sight of land.

The team considered other potential explanations, from the Coriolis effect to winds. “The one thing that best predicted the observed changes in shearwaters’ orientation was always this sun compass effect,” says Lewin.

The effect is small. After a 1000 km flight, a bird would have to fly only an extra 5 km to reach its colony, which, for such efficient long-distance fliers, is probably negligible, Lewin says. This might explain why Manx shearwaters haven’t evolved some mechanism for avoiding jet lag, he says.

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“What is good about the study is that they analyse a lot of tracks, making for robust data to test different models,” says at Macquarie University in Sydney.

While other species may get this form of jet lag, too, long-distance flights by birds are typically done during migrations, and migrations usually involve mainly north-south travel, says Cheng, so jet lag won’t be much of a problem.

However, near the poles, the travel distance required to cross 15° or more of longitude becomes so short that many animals might be affected, says Lewin, perhaps even including polar bears or Arctic foxes travelling on sea ice.

“Near-polar species may be quite strongly affected,” he says. “Now, it all gets a bit complicated because you have 24-hour daylight and 24-hour darkness in parts of the year, so circadian rhythms break down generally in some species.”

Giant waterlilies are not exactly inconspicuous plants. But in the past few years, we have discovered no fewer than three new species, taking the total to five. The latest species to be described was identified with the help of social media, satellite photos and a mad jungle dash in the dark.

“I think it’s incredible that we find something so new, which is so large, in this world where we think everything is already known,” says at the Botanical Society of Britain and Ireland, who has helped describe two of the new species.

Giant waterlilies are famed for their massive leaves, which grow up to 3 metres wide. For many decades, just two species were known: Victoria amazonica and Victoria cruziana. Then in 2016, Carlos Magdalena at the Royal Botanic Gardens in Kew, London, noticed that giant waterlilies grown from seeds from Bolivia were a bit different, with even larger leaves. In 2022, Magdalena and his colleagues published a paper showing that this was a new species, Victoria boliviana.

Magdalena hasn’t stopped there. In 2021, Jeremiah Harris, who runs a carnivorous plant business in the US, posted that he took while swimming near the Inírida river in Colombia next to what he assumed was V. amazonica.

Magdalena was struck by the photos because scientists had thought there were no giant waterlilies in this region. “This river is geographically completely separated from the Amazon, and has been for millions of years, and that is why this is such an interesting find,” says Christenhusz.

Magdalena, Christenhusz and their team examined satellite photos and found telltale green dots confirming there really were giant waterlilies growing there. They then organised an expedition to the region. The team found two plants but neither was flowering – and analysing the flowers is a crucial step in establishing whether a waterlily really is a new species.

At 11pm on the last night of the expedition, with the plane due to leave at 9am, the researchers seemed to have failed. Then one of the guides, Gustavo Melo from the Indigenous Tucano community, said he knew where some more giant waterlilies were growing. The team set off by boat in the dark, and found five plants in a small lake just before sunrise, including some that were flowering.

Magdalena, Christenhusz and their colleagues have now published a paper describing the new species, which they have named Victoria colombiana. It differs from V. amazonica in the orientation of the spines beneath the leaves, and in the shape of its flowers and fruits. The spines are a defence against manatees and plant-eating fish, Christenhusz says, so they vary between species depending on which herbivores are most prevalent.

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As far as the team is aware, V. colombiana is found in only one small area. A single event, such as a pollution spill, could wipe out the entire species, says Christenhusz. But the team is planning to try to collect seeds to help ensure the species survives.

Meanwhile, Magdalena also realised that the giant waterlilies growing in the Pantanal region of South America, hundreds of kilometres to the south-east of Colombia, must have been isolated from other populations for a very long time. Sure enough, genetic studies revealed that they are another distinct species, despite looking very similar to V. cruziana. Magdalena, Christenhusz and their colleagues will publish a paper soon to describe this fifth species, which they have decided to name Victoria mattogrossensis.