Have you ever wondered why you can’t tickle yourself? Or why some people are more ticklish than others? Or why certain spots on the body are more susceptible to tickling? Or why tickling is even a thing? Well, the Donders Institute in the Netherlands hopes to figure all of that out.
On behalf of the Donders Institute, a team of neuroscience researchers led by Konstantina Kilteni opened up a “tickling lab” at Radboud University in Nijmegen, Netherlands to test, research, and hopefully answer those questions and others that Socrates had over 2,000 years ago.
Tickle, tickle!
Nobody loves giving or receiving a good tickle more than a toddler.
Interestingly, tickling is one of the most understudied human behaviors that still puzzles neuroscientists.
In a recent paper summarizing what we know so far, here are five questions we still… pic.twitter.com/PqxhSSAg4J— Hasan Merali, MD (@Hasan_Merali) May 28, 2025
Kilteni believes that the research into tickling would not only give us answers to those questions, but also grant us better understanding of how our brains work and help us to see if there is any evolutionary benefit to tickling.
“If we know how tickling works at the brain level, it could provide a lot of insight into other topics in neuroscience,” said Kilteni. “Tickling can strengthen the bond between parents and children, for instance, and we usually tickle our babies and children. But how does the brain process ticklish stimuli and what is the relationship with the development of the nervous system? By investigating this, you can learn more about brain development in children.”
Kilteni also found an answer to why we can’t tickle ourselves, but the more interesting mystery they hope to find out is how.
“Apparently, our brain distinguishes ourselves from others, and because we know when and where we are going to tickle ourselves, the brain can switch off the tickling reflex in advance,” she explained. “But we don’t know what exactly happens in our brain when we are tickled.”
The tickling lab is conducting several different neurological tests and experiments regarding tickling that haven’t been seriously considered previously. One example is doing various tickling tests involving persons with autism to see if there are any patterns on a neurological level, given that they typically are more ticklish and sensitive to touch compared to non-autistic individuals. Other experiments involve testing different types of tickling and seeing how the brain reacts. While tickling is considered a catch-all term, being tickled by someone’s fingers in your armpit is different from when your feet are being tickled by a feather for example.
The current experiment involves the subject putting their feet into two holes positioned under a chair. A mechanical rod then tickles the foot soles. Meanwhile, the neuroscientists are measuring what’s going on in the brain along with the heart rate, perspiration, and laughter or screaming volume and duration during the session to find if there are any correlations.
“By incorporating this method of tickling into a proper experiment, we can take tickling research seriously,” said Kilteni. “Not only will we be able to truly understand tickling, but also our brains.”
Even though we are still discovering the various questions of “why tickling?” we have found some benefits to it. As Kilteni mentioned, the act of tickling can strengthen bonds between parents and children, close friends, and romantic partners. It’s also a fast-track method to create laughter, which has been shown to reduce stress, release dopamine, and boost your immune system, among other health benefits. There are also studies that show that tickling ears could even reduce aging in adults over 50 years old.
That’s not to say that everyone should just tickle everybody for their health. Some child experts say that even though a child laughs from being tickled, it doesn’t mean that they enjoy it. Tickling could overwhelm a child (or an adult for that matter) and have them not feel in control of their own body, with laughter being an automatic nervous submissive response to an aggressor rather than a sign of enjoyment. This plays into many of the questions we still have about tickling, in that the act doesn’t have a universal response. It’s important to ask and check if a person or child wants to be tickled before engaging in it.
With time and experimentation, the Donders Institute will hopefully find new discoveries about our brains that will tickle our curiosity.
Assistant Professor of Ecology & Evolutionary Biology, University of Tennessee; Smithsonian Institution
If you’ve ever felt overwhelmed by menu options at a restaurant, cereal varieties at the grocery store or potential partners while scrolling through dating apps, you’ve experienced choice overload.
People aren’t the only ones to have trouble making decisions when confronted with many options simultaneously. In our new study published in the journal iScience, my colleagues and I found similar effects of choice overload in female gray tree frogs when faced with too many calls from males looking for love.
Scientists have observed many species having similar decision-making problems when experiencing choice overload. But we know little about how these kinds of cognitive constraints affect animals in natural settings.
Indecision on the frog dating scene
The gray tree frogs we focused on live in wooded areas near sources of water in North America. During the mating season, males gather in choruses and call to attract mates. Females pick mates based on several call attributes, including call length. Longer calls are more attractive.
For our experiment, we captured 60 female tree frogs from breeding choruses in East Tennessee and brought them into our lab. Then we played recorded mating calls for each female, giving her a choice between one long, attractive “target” call and one, three or seven shorter, less attractive “distractor” calls.
In the wild, a tree frog breeding chorus can include dozens or even hundreds of calling males. In our lab setup, the calls played sequentially, so they never overlapped.
Females would hop toward the speaker broadcasting the call she preferred. As the number of distractor calls increased, females got worse at picking the attractive call, took longer to decide, and were more likely to defer choosing within the 10-minute window altogether.
View from above of the frog test arena, where researchers would place a female frog in the center and then play various male mating calls from speakers placed around the perimeter.Jessie Tanner
Cognitive confusion
Because we eliminated call overlap entirely, we know this decline wasn’t due to what researchers call energetic masking. That’s the well-documented problem of overlapping signals impairing an individual’s ability to detect and discriminate a signal from noise.
Biologists have long known that female preferences can weaken in choruses and have usually assumed the explanation is energetic masking: Too many overlapping signals create a challenge for the frogs’ perceptual systems. In other words, they can’t detect or discriminate individual calls.
Instead, our study shows that a female’s own cognitive limits can make it hard for her to select her preferred mate. The challenge comes from too many males to choose from, not being unable to hear the males clearly.
When females can’t make the optimal choice
Call traits are linked to offspring fitness in gray tree frogs. If females have trouble recognizing the calls they prefer in a real chorus, they aren’t able to pick the mates with the best genes to pass on. They may end up mating with males they would otherwise reject. These males with less going for them then pass on their less desirable traits, which could have negative consequences for the offspring.
Females’ cognitive overload could be an opportunity for males who might not otherwise get a chance to mate.Jessie Tanner
Our finding raises the possibility that males could exploit this cognitive limitation in females. Less attractive males might do better by joining bigger choruses, where the sheer number of competitors makes it harder for females to discriminate against them. Conversely, more attractive males may benefit from calling in smaller groups, or even in isolation. My colleagues and I hope to investigate some of these possibilities soon.
More options, more opportunities … to a point
We ran our experiments in a simplified lab arena, which allowed us to isolate choice overload from other effects. We removed the real-world clutter of overlapping calls, vegetation and risk from predators that females would face in an actual pond. We also limited female choice to eight calls, though frogs may hear even more in natural settings.
The next step in this research is figuring out how much choice overload matters in a real chorus, where calls do overlap, and where sensory processing and cognitive processing are probably both at play. We’re particularly interested in seeing whether, in natural choruses, decisions do take longer and females really end up mating with less preferable males.
Choice overload isn’t unique to frogs, or even to mate choice. Researchers have seen bees choosing among flowers, ants comparing potential nest sites and mosquitoes selecting egg-laying sites all making worse decisions as the number of competing options increases. And recent research on field crickets and tree frogs has found similar patterns in these animals as they pick mates based on their calls.
Together, this growing body of evidence suggests that cognitive constraints are a general feature of animal decision-making.
When water and boiling oil mix, the result can be explosive, as seen in this demonstration. U.S. Navy photo by Mass Communication Specialist 2nd Class Travis Alston/Released via Flickr
Associate Professor of Chemistry, University of Richmond
Deep-frying a turkey is a great way to get a delicious, moist meal for Thanksgiving. But this method of cooking can be a very dangerous undertaking.
Every fall, millions of dollars of damage, trips to the ER and even deaths result from attempts to deep-fry turkeys. The vast majority of these accidents happen because people put frozen turkeys into boiling oil. If you are considering deep-frying this year, do not forget to thaw and dry your turkey before placing it in the pot. Failure to do so may lead to an explosive disaster.
What is so dangerous about putting even a partially frozen turkey in a deep-fryer?
I’m a chemist who studies plant, fungal and animal compounds and have a love of food chemistry. The reason frozen turkeys explode, at its core, has to do with differences in density. There is a difference in density between oil and water and differences in the density of water between its solid, liquid and gas states. When these density differences interact in just the right way, you get an explosion.
If water and oil are in the same container, the denser water will sink to the bottom.Daniel Merino, CC BY-ND
Understanding density
Density is how much an object weighs given a specific volume. For example, imagine you held an ice cube in one hand and a marshmallow in the other. While they are roughly the same size, the ice cube is heavier: It is more dense.
The first important density difference when it comes to frying is that water is more dense than oil. This has to do with how tightly the molecules of each substance pack together and how heavy the atoms are that make up each liquid.
Water molecules are small and pack tightly together. Oil molecules are much larger and don’t pack together as well by comparison. Additionally, water is composed of oxygen and hydrogen atoms, while oils are predominantly carbon and hydrogen. Oxygen is heavier than carbon. This means that, for example, one cup of water has more atoms than one cup of oil, and those individuals atoms are heavier. This is why oil floats on top of water. It is less dense.
While different materials have different densities, liquids, solids and gases of a single material can have different densities as well. You observe this every time you place an ice cube in a glass of water: The ice floats to the top because it is less dense than water.
When water absorbs heat, it changes to its gas phase, steam. Steam occupies 1,700 times the volume as the same number of liquid water molecules. You observe this effect when you boil water in a tea kettle. The force of expanding gas pushes steam out of the kettle through the whistle, causing the squealing noise.
Frozen turkeys – or any kind of frozen meats, for that matter – contain a lot of ice. Raw meat can be anywhere from 56% to 73% water. If you have ever thawed a frozen piece of meat, you have probably seen all the liquid that comes out.
For deep-frying, cooking oil is heated to around 350 degrees Fahrenheit (175 C). This is much hotter than the boiling point of water, which is 212 F (100 C). So when the ice in a frozen turkey comes in contact with the hot oil, the surface ice quickly turns to steam.
This quick transition is not a problem when it happens at the very surface of the oil. The steam escapes harmlessly into the air.
However, when you submerge a turkey into the oil, the ice inside the turkey absorbs the heat and melts, forming liquid water. Here is where the density comes into play.
This liquid water is more dense than the oil, so it falls the bottom of the pot. The water molecules continue to absorb heat and energy and eventually they change phases and become steam. The water molecules then rapidly spread far apart from one another and the volume expands by 1,700 times. This expansion causes the density of the water to drop to a fraction of a percent of the density of the oil, so the gas wants to quickly rise to the surface.
Combine the fast change in density together with the expansion of volume and you get an explosion. The steam expands and rises, blowing the boiling oil out the pot. If that weren’t dangerous enough, as the displaced oil comes into contact with a burner or flame, it can catch fire. Once some droplets of oil catch on fire, the flames will quickly ignite nearby oil molecules, resulting in a fast-moving and often catastrophic fire.
Every year, thousands of accidents like this happen. So, should you decide to deep-fry a turkey for this year’s Thanksgiving, be sure to thoroughly thaw it and pat it dry. And next time you add a bit of liquid to an oil-filled pan and end up with oil all over the stove, you’ll know the science of why.
Squinting through my binoculars, I scanned the dense branches of a black spruce, trying my best to catch a glimpse of the thin legs of a small black, white and yellow songbird. I was on the hunt for a yellow-rumped warbler – a bird affectionately called “butter-butt” by bird-watchers after the distinctive buttery yellow patch of feathers above its tail.
Stephanie Szarmach holds a yellow-rumped warbler that was banded as part of a study.Johanna Beam
Once I spotted a flash of red on one of the bird’s legs, I knew that this individual was special – in fact, it was one that I already knew well. That’s because I had placed identifying bands on it the previous year as part of my Ph.D. research, and it was carrying a very important piece of new technology.
I played the high pitched “warble” of its song through a speaker placed below a mist net of fine, nearly invisible mesh. Thinking another male had intruded on his territory, the bird quickly descended. My tactic worked – he got caught in the net. As I gently removed him, I breathed a sigh of relief as I saw the Tic Tac-size device sitting on his back.
A yellow-rumped warbler wears a multisensor geolocator backpack.Stephanie Szarmach
Over the past year, this warbler carried a multisensor geolocator backpack throughout his migratory journey, recording the long trek from his breeding grounds in Anchorage, Alaska, to a yet unknown winter refuge and back again. Working with my Ph.D. adviser, evolutionary biologist David Toews, I deployed dozens of these cutting-edge tags to illuminate the migratory journeys of these high-latitude breeding warblers at a scale not previously possible for small birds.
Now, after a year of waiting, I finally had the data in hand.
How can scientists track small birds?
Researchers began tracking the movements of migrating birds in the late 1960s using radio telemetry, a technique that requires tagged birds to be physically followed with receiver equipment, sometimes aided by a small aircraft.
Then, as GPS became more widely available in the early 2000s, satellite tags let researchers accurately track birds remotely. However, GPS transmitters are hefty – even just the battery that powers them is too heavy to be carried by the majority of small migratory songbirds, which often weigh less than a spoonful of sugar.
To address this problem, researchers developed ingenious little light-level geolocators. These miniature tags minimize weight by containing only a tiny battery, clock, computer chip and light sensor. They store data internally rather than transmitting it – hence my need to recapture tagged birds a year later. Researchers infer a bird’s locations from the timing of sunrise and sunset, which vary predictably across the globe and throughout the year.
Light-level geolocators have openednew windows into themigrations of small birds, but they also have limitations: Their estimated locations can err by hundreds of miles, and this uncertainty becomes impractically high around the equinoxes, when day length is the same worldwide.
Each harness loop of the multisensor geolocator goes around one of the bird’s legs and the tag sits on the bird’s lower back.Stephanie Szarmach
More recently, researchers developed a newer method of geolocation that uses atmospheric pressure to circumvent these limitations. When a bird ascends during a migratory flight, a barometric geolocator records a steep drop in air pressure, capturing the timing of departure and arrival for every stop along a bird’s migration route. In between flights, the pressure the tag records reflects the elevation at the bird’s position.
Knowing the bird’s elevation helps to narrow down possible locations, which researchers can then refine further by comparing the change in pressure over time recorded by the tag to global weather data using the computer program GeoPressureR. The unique pattern of rises and falls in pressure acts as a kind of pressure fingerprint for a specific location. Including light and wind data in the model of the bird’s movements can increase precision even more.
Atmospheric pressure data collected from a multisensor geolocator carried by a yellow-rumped warbler over five days in spring. When the bird is stationary, such as when resting at a stopover site, the measured pressure remains steady. During migratory flights, when the bird ascends into the sky, the pressure drops and fluctuates dramatically.Stephanie Szarmach
New tech answers an old question
We used these new multisensor backpacks to study the migration patterns of myrtle warblers, the northern subspecies of yellow-rumped warbler, which breed across North America’s boreal forest. Myrtle warblers in the northeast are known to winter along the Atlantic and Gulf coasts, but where northwestern populations migrate has been more of a mystery. In 1899, ornithologist Richard McGregor observed myrtle warblers wintering in coastal California, and hypothesized that these birds might breed in Alaska and British Columbia.
Using these new tags allowed us to test whether warblers breeding in Anchorage, Alaska, actually followed the shortest migration route to winter in California. To our surprise – and probably to McGregor’s as well, if he were still alive – we found that all the birds we tracked traveled east across the boreal forest of Canada before shifting south to the Gulf Coast – certainly not the Pacific Coast route we expected.
All told, this 6,800-mile (10,900-kilometer) round-trip journey was much longer than we anticipated for a species commonly considered a short- or medium-distance migrant.
Researchers tracked the routes six myrtle warblers flew on their fall migration southeast from Anchorage, Alaska.Figure by Stephanie Szarmach. Warbler illustration by Emily Griffith
Why take such a circuitous route?
The long, seemingly suboptimal route taken by our Alaskan myrtle warblers is actually mirrored by some other songbird species tracked from northwestern North America, including blackpoll warblers and Swainson’sthrushes.
Part of this pattern may relate back to the glaciations that isolated ancient populations of birds millions of years ago. The thinking goes that as these glaciers spread, they squashed the ranges of formerly northern species into the south. Then, as the glaciers slowly receded, the forests gradually reexpanded.
As more land opened up, birds moved farther north and west into that habitat. Each season some birds went a little farther as the forest available in their northern breeding grounds expanded. For migratory species such as myrtle warblers, the farther north and west their breeding range expanded, the longer the migration to their southern wintering ground became.
Scientists think migration routes are genetically encoded. The birds’ genes may have traced this expansion front, like Hansel and Gretel putting down breadcrumbs as they journeyed deeper and deeper into the forest. Today’s migration routes still trace that incrementally expanded path, even though the glaciers that shaped the original boundaries are long gone.
We’re still not sure exactly where the California-wintering myrtle warblers spotted in the 1800s are breeding. We suspect that a small proportion of the Anchorage-breeding birds may migrate to California, but that most of them travel from more distant, unstudied regions of Alaska or Yukon. Future research, potentially tagging myrtle warblers directly on the California wintering grounds, will shed more light on this population and why certain individuals follow a different migration route.
Barometric geolocation provides new data
Today, this new geolocation approach improves scientists’ ability to study the migrations of small birds and supports more effective conservation actions across the course of the entire year. More precise location estimates help researchers identify key stopover and wintering sites in need of protection and better understand the threats birds face throughout their journeys. These geolocators also reveal the altitude of migratory flights, which is important for understanding the risk of birds colliding with buildings or wind turbines.
Because these new tags capture pressure data for every migratory flight, they’re especially valuable for studying migration timing. Researchers have combined data from over 50 bird species to understand at what time of day or night different birds migrate. Now, as a postdoctoral researcher at the Smithsonian Migratory Bird Center, I am integrating multisensor geolocator data with satellite imagery to investigate how arrival and departure decisions throughout a bird’s migratory journey relate to seasonal changes in plant growth.
Scientists have now tracked dozens of bird species with multisensor geolocators, and that number increases every year. Each mapped migratory journey improves our understanding of how small birds migrate, what factors shape their movements and how best to protect them.
