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Why stress hormones can trigger sudden ‘brain freeze’ in interviews, exams or live broadcasts - and what you can do about it. Also: smart textiles, building with popcorn, a tool-using cow and vital aquatic fungi.
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00:06your mind goes blank it happens to practically everyone at some point often in stressful
00:12situations like during an exam or job interview but what exactly is going on in your head in
00:19moments like these knowledge isn't erased but you suddenly lose access to it your brain just
00:26seems to freeze up right when it matters most learn why it happens and much more this time
00:34on dw science show welcome to tomorrow today he's performed the role many times but suddenly
00:45can't remember what comes next journalists and live broadcast situations know the feeling too
00:54and so do applicants in job interviews cognitive psychologist Christian Mertz and his team study
01:04these kinds of memory lapses what triggers it is when stress hormone levels suddenly rise too high
01:14especially in situations we can't control like oral exams or job interviews we go into the
01:22situation it matters to us we don't want to make a bad impression and then we get so stressed out
01:29that we suddenly can't remember a thing we try an experiment sending test subject Leander into a
01:38simulated stressful situation he's applying for a job as a teacher at the start his blood pressure
01:45and heart rate are checked both are normal a saliva sample reveals levels of the stress hormone cortisol
01:52around 7.5 nanomoles per liter that's pretty standard for this time of day he still doesn't know what's
02:01coming this and off I'm a little nervous because of the whole situation but overall still feel pretty
02:07relaxed that's about to change in the first part of the test Leander has just two minutes to memorize 30
02:16items from a shopping list he's then given a blank sheet of paper and told to write down all the
02:24items he
02:25can remember Leander can recall 20 he'll repeat the memory test in a little while but first comes
02:37the simulated job interview to start he's been told to speak freely for several minutes about why he
02:44thinks he would make a good teacher at first things go smoothly he begins by saying that he's very goal
02:51oriented but the situation makes it hard to remain relaxed and confident he's being filmed so isn't
03:01allowed to move the interviewers remain distant there are no smiles or nods of encouragement Leander grows
03:09increasingly tense before he knows it he's talking about his weaknesses and how to turn them into
03:16his strengths then the interviewer asks him to talk some more about his personal qualities
03:27that's actually a neutral sentence but some interviewees interpret it very negatively because
03:33they read meaning into it and that makes the situation stressful two people sitting there judging you
03:41and the stress isn't over Leander still has to repeat the shopping list test before the job interview he
03:48remembered 20 out of 30 items after the interview just 12 an indicator of elevated stress and his
03:57cortisol levels confirm it 9.3 nanomoles per liter unquestionably higher than before the result is clear
04:05stress affects memory though it never grew so critical that Leander's mind went blank
04:16that can happen even to experienced journalists like Hannah Resch she was reporting live from Tel
04:24L'aviv when suddenly so even professionals aren't immune what happens in moments like these stress
04:51stress hormones put the entire body on high alert respiration rate and blood pressure rise the
04:57bronchi widened blood flow to the muscles increases physical response is crucial to either fighting or
05:04fleeing cortisol also affects the brain especially the hippocampus under normal circumstances it's
05:12responsible for retrieving stored information so it plays a key role in memory cortisol temporarily blocks
05:20memory retrieval shifting focus entirely to the present neurons begin transmitting
05:25information less effectively or not at all your mind goes blank it's difficult to get out of this situation
05:34without help help when your brain seems to freeze up some professions plan for it actors have prompters to
05:47come to the rescue when your mind suddenly goes blank seemingly without warning what helps take a deep breath or
05:58two step back and create some mental distance with a little help it can happen so briefly that hardly anyone
06:07notices
06:09but the best protection against a blanking mind remains good preparation
06:13preparation is key it gives you confidence and that can reduce stress because you feel ready
06:23on the other hand it also depends on what you perceive as a stressful situation
06:30and there you can also learn to reframe it for yourself maybe to view it as a challenge rather than
06:37as a situation that you can't cope with so you can practice a relaxed approach to stress to cope when
06:46your mind seemingly abandons you when the lights in your brain turn back on you'll remember that the world can
06:55also be a beautiful colorful place with the occasional rainbow which brings us to a question sent in by a
07:02viewer from Georgia
07:05why do rainbows have seven colors and where do they come from
07:10the sun drenches our planet in different kinds of radiation waves of energy that have many different lengths
07:18most are invisible like infrared radiation for instance which makes you feel warm or UV radiation which
07:27causes sunburn the range is wide in a narrow window though when the waves are between 380 and 780
07:37nanometers long we can see them that's what we call the visible spectrum when all of those wavelengths are
07:44mixed together in sunlight they look white but under the right conditions that white light can be split
07:51into its individual colors and that's when we see a rainbow people often say the rainbow has seven colors
07:58mostly because that's what Isaac Newton decided during his revolutionary prism experiments there are
08:05actually no clear boundaries between one color and the next in the visible spectrum though a rainbow is a smooth
08:12progression from violet with the shortest waves to red with the longest the colors appear when
08:19countless water droplets hanging in the air acts like tiny prisms this is how it works because water is
08:28optically denser than air light slows down when it passes through a droplet this alters its path a process
08:35called refraction the light then bounces back off the inner surface on the opposite side depending on how
08:42long or short they are the different wavelengths slow by different amounts so they spread out and
08:49leave the droplet at slightly different angles the white light has been split but for us to see a
08:56rainbow a few things have to line up perfectly first the air in the direction you're looking has to contain
09:03huge numbers of droplets which is why you usually see them around the time it rains second the Sun has
09:10to be
09:10behind you and fairly low in the sky and third the light has to strike the raindrops in front of
09:16you at
09:17an angle of 42 degrees that's why you might also spot rainbows near waterfalls on sunny days because of the
09:27droplets in the spray so stand in the right place at the right time with the Sun shining on moist
09:34air and you
09:35may just catch a glimpse of one of nature's most colorful displays what are stars made of how many
09:44colors can butterflies see could robots have babies one day do you have a science question send it to
09:52us as a video text or voice message if we answer it on the show we'll send you a small
09:58gift as a thank
09:59you so just ask time now to go on an expedition to a hidden watery world where a group of
10:09small
10:10often overlooked organisms play a key role in ecosystems in rivers and streams microscopic
10:16fungi are a vital link in food chains and also help keep habitats clean and future they may even inspire
10:25new
10:28medicines it feels a little like a treasure hunt but what these researchers are searching for in a
10:34creek in this idyllic valley in Switzerland is invisible to the naked eye and mostly unknown to
10:40science organisms that until now have been largely ignored and I'm gonna present okay molto similar on
10:47some look like mosquitoes others have oval shapes like bacteria and yet others have four arms they're
10:57all different they're also really beautiful the researchers share a great passion for a tiny
11:07fungi the team from the University of Applied Sciences and Arts of southern Switzerland is part of an
11:14international research project on aquatic fungi the same group of fungi is also found in forest soil closely
11:25related species in evolutionary terms people may know more about them in that context they form mycelia
11:33in the forest and produce similar enzymes to break down wood and leaves what would happen if leaves in
11:41the forest didn't decompose eventually you'd get mountains of them that aren't being used bacteria will cause the leaves to
11:49rot
11:49somehow but they wouldn't be returned to the ecosystem the way they are when fungi are involved
11:58aquatic fungi help clean water and also provide food for aquatic insects like caddisfly larvae which wrap themselves in leaves
12:07the larvae are in turn a food source for fish birds and birds and
12:11amphibians when they are eating the leaves when they are eating the leaves they eat the fungi together with the
12:17leaves so sometimes
12:18we make the joke is like a crackers with butter right so the crackers are nice but if they have
12:23butter they are nicer
12:24Isabel Fernandes from the University of Minho in Portugal is also fascinated by aquatic fungi she leads the specialist group
12:34at the International Union for Conservation of Nature
12:39Back in the lab the samples are stained and fixed
12:44The tension mounts and the researcher quickly spots an old friend
12:51This is a very very gorgeous one actually this clavariopsis aquatica was one species that about 20 years ago more
12:58or less I think
12:59It was studied by some colleagues from France and they found out that it has the capacity to produce some
13:06antibiotics
13:06A fascinating world appears under the microscope
13:10About 5700 species of aquatic fungi have been described worldwide so far
13:16As we learn more about them new applications might emerge in fields like cancer research says Andreas Bruda
13:25But the goal of the ongoing project is simply to learn more about aquatic fungi
13:31And how to protect them their habitats are under serious threat
13:35It's important that when we think about biodiversity we don't only think about the normal biodiversity we are used to
13:44look at like elephants and lions which are super important of course to protect
13:49But we also look at these very tiny microscopic organisms that play such important roles in our freshwater ecosystems
13:57From a human perspective drinking water and drinking water quality are the main arguments
14:03But it's also about an ecosystem one that either functions or doesn't
14:10A microorganism could soon appear on a conservation list for the first time
14:15And by then the researchers work might well lead to the discovery of even more hitherto unknown species of aquatic
14:23fungi
14:26Antibiotics sourced from aquatic fungi
14:29Invention is often just using stuff in new ways
14:32Like in our next story where researchers have developed building materials based on a popular movie theater snack
14:43Popcorn is delicious
14:47And it can also be used in ways you never considered
14:53Those products are the brainchild of this man
14:59My name is Ali Reza Karazepor
15:02I'm a materials researcher and product developer
15:04And I work with popcorn
15:11It's not just tasty but perhaps also a material for the future
15:15It all starts with this
15:17A shredded version of what you can buy at the movies
15:20This is a popcorn granulate made by mechanically shredding kernels
15:29The popped and shredded kernels are sorted into specific granule sizes
15:39To turn it into a useful material, the popcorn is mixed with a binding agent and pressed
15:46Cold at first
15:48But then baked in an oven
15:51Though at temperatures under 200 degrees Celsius
15:55Not unlike a cake
16:02We make important products
16:05For example insulation boards suitable for indoors and outdoors in construction
16:12Kharazipur's university is still discussing production of insulation with manufacturers,
16:17but other products are already out there, like compostable packaging, kids' toys, or
16:25lightweight panels for installation in camper vans.
16:31A test shows just how stable they are when given a typical furniture finish.
16:38With this very thin coating, we achieve extremely high tensile strength at a very low overall
16:44weight.
16:45It outperforms by far a conventional particle board, or MDF.
16:53All the researchers here are convinced the material has a bright future.
16:59It's a raw material we could really use today because we urgently need new options, especially
17:06when it comes to materials that we can use now, but also compost later.
17:13Taking a stance against the tsunami of plastic, Ali Reze Kharazipur has already filed more than
17:19ten patents.
17:20The idea came to him while eating popcorn at the movies.
17:24It was so soft.
17:28I thought, you could make more products from popcorn, especially with wood-based materials.
17:36That's when the idea was born.
17:41His research began in his kitchen.
17:46I bought some kernels and simply popped them here.
17:53The first product, 17 years ago, was a particle board made from wood mixed with popcorn.
17:59Ali Reze Kharazipur has since retired, but his successor is also fascinated by popcorn's properties.
18:05And he's working to ensure it one day finds wider use in construction.
18:14Textiles are also a hotbed of innovation at the moment.
18:18Some are meant to cool you down.
18:20Others you can switch on and off like a light, while yet others can connect to the internet.
18:25Fabrics nowadays can come with a range of surprising and fascinating functions.
18:30We looked at three different types of smart textiles that are currently under development.
18:39Sometimes they think I'm crazy.
18:41Smart textiles, clothing with built-in sensors.
18:47This is meant to restore the connection between the brain and the hand.
18:52Sometimes it's just to provide a little tingle, like with a special technique.
18:56ASMR is supposed to relax and lower anxiety.
19:06The dance floors of Berlin's techno scene.
19:09Pulsing electronic beats that can make you forget everything else and tap into your inner
19:14creativity.
19:15An idea that can be expanded on.
19:19Why not attach copper plates to a t-shirt?
19:22Wire them up, connect them to an electrical source, and turn yourself into a human beatbox.
19:28With the right music software, electrical impulses become sound.
19:33Each of it, it's a channel.
19:35And you can see that, for example, I can do some snare here.
19:39Tss, tss, tss.
19:40While I loop the, the kicks, like.
19:43Tss, tss, tss.
19:44And then it will integrate with each other, doing like.
19:47Tss, tss, tss, tss.
19:48And this is that I can do it while I'm like wearing it.
19:53Atil Amer studies product design in Berlin.
19:57He was born in Syria.
20:01He's a refugee who fled to Europe, where he began experimenting with sound and tinkering
20:07with his t-shirt.
20:10On regular base, I lost contact with my family because there wasn't like, uh, proper connections
20:16and internet.
20:17And even like, life supplier like flour or water.
20:22Greiz, a town in southeastern Germany, is home to a renowned textile research institute
20:28that also develops smart textiles.
20:31Here, electrically conductive elements can be stitched directly into the fabric, like
20:36in this therapeutic glove.
20:42Stroke patients often experience paralysis in their limbs.
20:46They can put on this glove and a specific program causes weak electrical impulses to be
20:52sent to the fingertips.
20:53This is to restore the connection between the brain and the hand, allowing them to grasp
21:00things again.
21:03The glove is already on the market.
21:06Its manufacturer says it can be used up to 100 times.
21:10But like most smart textiles, it shouldn't be run through a washing machine.
21:15Before going on sale, a smart textile should be able to withstand being washed by hand at
21:21least 30 times.
21:23But we're not talking machine washing yet.
21:29Back to Berlin and Chilean artist Nicole Schonher.
21:34She's developed special smart home accessories.
21:41With the interaction of touching the different textures and playing sounds at the same time.
21:48So this play of multi-sensorial engagement gives you a moment of calm and rest that lets
21:55you focus on what you're engaging with instead of thoughts from your day-to-day life or stress
22:03from work.
22:18What happens at the crossroads where art and science meet?
22:23The creative possibilities offered by smart textiles are far from exhausted.
22:29It's just to give the DJ or performance more like freedom to move around, to make some
22:37movement, to create some kind of vibe for the people in the room.
22:47We humans aren't the only animals to use tools.
22:51Chimpanzees, for example, crack nuts with sticks or stones.
22:55Not exactly known for this behavior, on the other hand, bovines.
22:59Which is why, in January of 2026, an Austrian cow made international headlines.
23:07Veronica the cow usually lives a peaceful, quiet life.
23:11But for a few days in January, she was at the center of a media frenzy.
23:17The Washington Post, the New York Times, Le Figaro, The Guardian, the Süddeutsche Zeitung.
23:26It was unbelievable.
23:28There was global interest in my witch.
23:34That's what Witka Wiegeler calls his pet, who shot to fame thanks to this video.
23:39In it, she uses tools, and not just in random ways.
23:44When her back itches, Veronica reaches for her brush.
23:48If her belly is in need of a scratch, she pokes around more gently with the stick end.
23:53The actions are self-taught.
23:56Up to now, no one knew cows could use tools.
23:59The ability made Veronica the star of a scientific study.
24:03But its author, Alice Auersberg, says the bovine may not even be unusually smart.
24:09It could be that she simply lives an unusual life.
24:12Veronica is not a production animal.
24:17She's a beloved pet.
24:18And she's been surrounded by many objects her whole life that she could access, interact
24:23with and learn from.
24:26And she was allowed to grow old.
24:29Veronica is now 13, so she's had plenty of time to perfect her technique.
24:35That doesn't mean every cow would automatically use tools if they were available.
24:40This is an individual invention practiced by Veronica and a few other cows.
24:44But cows can invent, and they can create solutions to technical problems.
24:50We already know of other clever animals able to use tools.
24:54Still, experts were surprised that a cow exhibited such behavior.
24:59It's a wake-up call.
25:03Everyone talks about impressive cognitive abilities in chimps or dogs.
25:07But we should be paying more attention to our farm animals, investigating what they can
25:12do and drawing conclusions for their keeping and their needs in animal-friendly husbandry.
25:20It's likely other cows are just as clever as Veronica.
25:24They simply never had the opportunity to show it.
25:35That's all we have time for now.
25:40But we hope you'll join us again soon for more exciting stories from the worlds of science
25:46and technology, here on Tomorrow Today.
25:51See you then.
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