# Why can't you tickle yourself? (Science, Part 1) ![[images/Why-Cant-You-Tickle-Yourself-Science-Part-1.webp]] **Creator:** Joel is Curious · **Published:** 2026-11-09 · **Length:** 1:57 (YouTube Short) · [Watch on YouTube](https://www.youtube.com/watch?v=O0WnJTKjdjw) > Caption source: **YouTube auto-generated English captions (en-orig)**, fetched with yt-dlp (android_vr client) on the second try (the first request for the `en` track got HTTP 429). No TubeAlfred credits were used. About 460 words; timestamps are from the captions. The short is a vertical talking-head take outdoors in front of yellow autumn leaves and mountains (olive quilted hoodie), with a "Science incoming!" sticker at the start, burned-in captions and dark diagram cards: a "Blakemore et al., UCL, 1999 · 16 people, eyes closed" drawing of the two-robot setup ("you, through the robots: tickled less"), a "how tickly it felt / the foam moves late" bar chart (on time, 0.1 s, 0.2 s, 0.3 s late, robot on its own; "14 of 16 never noticed a delay"), and three "your brain → a command → your muscles / a note of what it sent → what it will feel like" flow diagrams for self-touch, "SOMEONE ELSE touches you" and "YOU, through the ROBOT, LATE" ("no match: it tickles again"). The thumbnail is a "PART 1 Science" title card. Screenshots are one about every 20 s. ## Summary "Why can't you tickle yourself? Try it right now. Find a spot where you're ticklish. It doesn't tickle the same, does it? But scientists found a way to make your own touch tickle using robots." In 1999 Sarah-Jayne Blakemore, a PhD student in London, tested it with two colleagues and two robots. Sixteen people sat with their right palm facing up and their eyes closed. Above the palm was one robot with a little piece of foam; their left hand held a handle for another robot. Moving the handle back and forth moved the foam back and forth on their palm, "so they were trying to tickle themselves through robots." Other times the robot moved the foam on its own with the same motion. Each time the subjects rated the touch, including how ticklish it felt. When the robot moved the foam on its own, it tickled more; when they did it themselves through the robots, it tickled less, "just like when you try to tickle yourself." In other trials Blakemore's team made the robot wait: the foam moved a tenth of a second late, then two tenths, then three, "and the tickle feeling came back." The longer the delay, the more it tickled, until at about two tenths of a second it tickled about as much as the robot did on its own. "14 of the 16 people said that they never even noticed a delay." Scientists think it's because of what your brain does every time you move. It sends a command to your muscles and keeps a note of what it sent; from that note it predicts what the movement will feel like. When the touch matches the prediction, the brain turns the feeling down. When someone else touches you, there's no command to predict from, so the feeling isn't turned down; and when the touch comes late, it doesn't match the prediction, so it can feel like a tickle. The researchers think this is how the brain keeps track of "what's you and what's something else." Your hands brush your face and body all day; turning down those touches may help a touch from something else stand out, "like a bug on your arm or a snake on your leg." It closes: "Your brain is always predicting what's next. So by now, it already knows what I'm going to ask" (to send the video to someone ticklish). ## Outline ### 0:00 Try it - [0:00](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=0s) "Why can't you tickle yourself? Try it right now. Find a spot where you're ticklish." - [0:03](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=3s) "It doesn't tickle the same, does it?" - [0:04](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=4s) "But scientists found a way to make your own touch tickle using robots." ![[images/Why-Cant-You-Tickle-Yourself-Science-Part-1-t0003.webp]] ### 0:09 Two robots, one palm - [0:09](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=9s) "In 1999, Sarah Jane Blakemore, a PhD student in London, tested it with two colleagues and two robots." - [0:14](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=14s) "16 people sat there with their right palm facing up and their eyes closed." - [0:18](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=18s) "Above that palm was one robot with a little piece of foam. Their left hand held a handle for another robot." - [0:23](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=23s) "When they moved the handle back and forth, the foam moved back and forth on their palm." - [0:26](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=26s) "So they were trying to tickle themselves through robots." ![[images/Why-Cant-You-Tickle-Yourself-Science-Part-1-t0023.webp]] ### 0:29 Self vs. robot - [0:29](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=29s) "Other times, the robot moved the foam on its own with the same motion." - [0:33](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=33s) "Each time, the subjects rated the touch, including how ticklish it felt." - [0:35](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=35s) "When the robot moved the foam on its own, it tickled more." - [0:38](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=38s) "When the subjects did it themselves through the robots, it tickled less, just like when you try to tickle yourself." ![[images/Why-Cant-You-Tickle-Yourself-Science-Part-1-t0043.webp]] ### 0:44 Making the robot wait - [0:44](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=44s) "In other trials, Blakemore's team made the robot wait." - [0:47](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=47s) "The foam moved a tenth of a second late, then two tenths of a second late, then three, and the tickle feeling came back." - [0:52](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=52s) "The longer the delay, the more it tickled until about two tenths of a second, where it tickled about as much as a robot did on its own." - [0:58](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=58s) "14 of the 16 people said that they never even noticed a delay." - [1:02](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=62s) "So even a delay that most of them didn't even notice made a difference." ![[images/Why-Cant-You-Tickle-Yourself-Science-Part-1-t0063.webp]] ### 1:06 The brain's note - [1:06](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=66s) "Scientists think it's because of what your brain does every time you move." - [1:09](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=69s) "It sends a command to your muscles and it keeps a note of what it sent." - [1:12](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=72s) "From that note, it predicts what the movement will feel like." - [1:16](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=76s) "When the touch matches the prediction, the brain turns down the feeling." - [1:20](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=80s) "When someone else touches you, there's no command from your brain to predict what it'll feel like. So the feeling isn't turned down." - [1:25](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=85s) "So when the touch comes late, it doesn't match what your brain predicted and it can feel like a tickle." ![[images/Why-Cant-You-Tickle-Yourself-Science-Part-1-t0083.webp]] ### 1:30 What's you and what's something else - [1:30](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=90s) "The researchers think this is how the brain keeps track of what's you and what's something else." - [1:34](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=94s) "Your hands brush your face and your body all day long." - [1:38](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=98s) "Turning the volume down on those touches may help a touch from something else stand out more, like a bug on your arm or a snake on your leg." - [1:44](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=104s) "That may be why it tickles when someone else does it, but not when you do it yourself." - [1:47](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=107s) "So send this to someone who's ticklish or someone who just likes science." - [1:50](https://www.youtube.com/watch?v=O0WnJTKjdjw&t=110s) "Your brain is always predicting what's next. So by now, it already knows what I'm going to ask." ![[images/Why-Cant-You-Tickle-Yourself-Science-Part-1-t0103.webp]] ## Anti-evolution argument *None in this video.* It's the first part of a new "Science" series and makes no argument for or against evolution or an old Earth; it doesn't mention creationism. The only evolution-adjacent remark is the closing suggestion that turning down self-touch "may help a touch from something else stand out more, like a bug on your arm or a snake on your leg," a functional explanation offered without any evolutionary claim. ## Answer *No anti-evolution argument to answer. Instead, a point-by-point check of the video's science against the study and the papers in the description. Numbers refer to the References table.* ### 1. The two-robot experiment - The 1999 paper describes exactly this setup: "A tactile stimulus on the palm of the right hand was either externally produced, by a robot or self-produced by the subject. In the conditions in which the tactile stimulus was self-produced, subjects moved the arm of a robot with their left hand to produce the tactile stimulus on their right hand via a second robot" [R1]. The stimulus was "a piece of foam (radius, 1 cm and length, 2.5 cm)" on a Phantom haptic robot, moving sinusoidally at 2 Hz over 1.5 cm; subjects "shut their eyes throughout the experiment" [R1]. - Subjects: "A total of 16 normal right-handed subjects (age range 19 to 30 years)" [R1]. The video says they "sat there," which matches ("Subjects sat at a table with their right forearm laid on the table with the palm facing upward"). - The result: subjects "consistently rated self-produced tactile stimuli as less tickly, intense, and pleasant than externally produced tactile stimuli" [R1]. As the description notes, these were ratings from 0 ("not at all") to 10 ("extremely"), not laughter; and the experiment was presented to subjects as being about "tactile sensation," not tickling, to avoid bias [R1]. ### 2. The delays - "In the delay conditions 100-, 200-, and 300-msec delays were introduced ... Subjects were not informed of the presence of these delays" [R1]. Tickly ratings rose significantly "as the delay ... increased from 0 to 200 msec," and there "was no significant difference between ratings at 200- and 300-msec delay and in the externally produced tactile stimuli condition" [R1]. So "about two tenths of a second, where it tickled about as much as a robot did on its own" is accurate. - Small nuance: the video's "a tenth of a second late, then two tenths ... then three" sounds like a sequence; in the study the conditions were "randomized and counterbalanced within and between subjects" [R1]. The finding is the same. - "14 of the 16": "Two subjects reported noticing the delay in the delay conditions in the postexperiment debriefing. The other 14 subjects claimed to be unaware of the delays" [R1]. Accurate. - The description's extra detail is also accurate: with the hand moving at a right angle (90°) to the foam, there "was no significant difference between ratings at 90° and in the externally produced tactile stimuli condition" [R1]. ### 3. "The brain keeps a note of what it sent" - This is a plain-English version of the efference copy / forward model idea. The authors "propose that the extent to which self-produced tactile sensation is attenuated (i.e., its tickliness) is proportional to the error between the sensory feedback predicted by an internal forward model of the motor system and the actual sensory feedback produced by the movement" [R1]. The 1998 paper defines "'efference copy', a copy of the motor command" [R2]. "Turns down the feeling" is fair: the authors say complete cancellation "may not be appropriate for the somatosensory system because it would result in anaesthesia," so the touch is attenuated, not erased [R1], matching the description's "Your own touch still tickles a bit, just less." - Where it happens: the 1998 fMRI study found more somatosensory-cortex activity for external touch and proposed that "the cerebellum is involved in predicting the specific sensory consequences of movements" [R2]. A 2020 study found that the stronger the coupling between the cerebellum and somatosensory areas, the more people attenuated their own touch [R5]. The description's "How the brain does this is still being worked out" is fair; that paper itself mentions "conflicting results about the role and the location of cerebellar activity" in earlier work [R5]. ### 4. "What's you and what's something else" (the bug on your arm) - The 1999 paper says: "externally produced stimuli normally carry more biological significance than self-produced stimuli," and attenuation "allows unexpected stimulation to be selectively detected" [R1]. The bug and snake are the video's own examples of that idea. - Supporting this, people with auditory hallucinations or passivity experiences did not rate their own touch as less intense or tickly than the experimenter's, which the authors read as "an abnormality in the self-monitoring mechanism that normally allows us to distinguish self-produced from externally produced sensations" [R6] (added context, not in the video). ### 5. "Tickling needs surprise" (description) - The paper addresses this directly: "Perhaps tickle requires an element of surprise," but in its robot condition the external stimulus "was highly controlled and highly predictable in time and space ... Therefore lack of stimulus predictability could be ruled out as a factor responsible for increasing tickliness rating in this condition" [R1]. The description's summary is accurate. (The paper also notes that subjects learned the 90° perturbations within seconds yet still rated them more tickly.) ## Key takeaways - Your own touch feels less tickly, less intense and less pleasant than the same touch from outside; Blakemore's two-robot experiment showed this in 16 people with ratings, not laughter. - Delaying the robot by 0.2-0.3 s made self-produced touch about as tickly as the robot's own, though 14 of 16 people never noticed the delay. - The leading explanation: the brain keeps a copy of each movement command, predicts the resulting touch and turns it down when it matches; a late or external touch doesn't match. - Turning down self-touch may help outside touches (a bug, a snake) stand out; the cerebellum appears to play a part, and the details are still being worked out. ## Things mentioned ### People - Sarah-Jayne Blakemore; Chris D. Frith and Daniel M. Wolpert (her two colleagues, named in the description); L. Weiskrantz, J. Elliott and C. Darlington (1971 study, description) ### Ideas - Self-produced vs. externally produced touch; sensory attenuation; efference copy ("a note of what it sent"); internal forward model; prediction error; telling self from other ### Things - Two robots (Phantom haptic interfaces in the paper); a piece of foam; delays of 0.1, 0.2 and 0.3 s; right-angle trajectory perturbation (description) ### Animals - A bug on your arm; a snake on your leg (examples) ### Links from the description - https://doi.org/10.1162/089892999563607 · https://doi.org/10.1038/2870 - https://joeliscurious.com · https://www.instagram.com/joeliscurious/ · https://www.tiktok.com/@joeliscurious · https://x.com/JoelisCurious · https://www.youtube.com/@joeliscurious ## Claims check | Claim in the video | Verdict | Source or note | |---|---|---| | In 1999 Sarah-Jayne Blakemore and two colleagues in London tested self-tickling with two robots | **Accurate** | Blakemore, Frith & Wolpert, UCL, *J Cogn Neurosci* 1999 [R1] | | She was a PhD student at the time | **Accurate** | PhD from UCL in 2000, co-supervised by Wolpert and Frith [R7] | | 16 people, right palm up, eyes closed, foam on one robot, left hand on another | **Accurate** | Methods [R1] | | The robot's own touch tickled more; self-produced touch through the robots tickled less | **Accurate** | Rated less tickly, intense and pleasant [R1] | | Delays of 0.1, 0.2, 0.3 s; tickle rose with delay and at ~0.2 s matched the robot's own | **Accurate** | No significant difference at 200-300 ms vs. external [R1]; delays were randomized, not stepped in order | | 14 of the 16 never noticed a delay | **Accurate** | "The other 14 subjects claimed to be unaware of the delays" [R1] | | The brain keeps a copy of each command, predicts the feel and turns down matching touch | **Accurate (the authors' proposal)** | Forward-model explanation [R1, R2]; supported by later imaging [R5] | | This helps the brain tell what's you from something else (a bug on your arm) | **Accurate (as the researchers' hypothesis)** | "Unexpected stimulation to be selectively detected" [R1]; self-monitoring [R6] | | Description: 1998 *Nature Neuroscience* paper is "the same team's first robot study" | **Partly accurate** | It's mainly an fMRI study using a foam-on-a-rod device; it reports the robot findings briefly, citing a 1998 *NeuroImage* abstract and unpublished data [R2] | | Description: robot's predictable touch still tickled more, so surprise isn't required | **Accurate** | The paper's own argument [R1] | ## References | # | Source | Exists? | Use in the video / role | Link | |---|---|---|---|---| | R1 | Blakemore, Frith & Wolpert, "Spatio-Temporal Prediction Modulates the Perception of Self-Produced Stimuli," *Journal of Cognitive Neuroscience* 11(5):551-559 (1999) | **Exists** (full text read, Wolpert lab PDF) | Description source: the whole experiment; **accurate**, in context | [doi:10.1162/089892999563607](https://doi.org/10.1162/089892999563607) · [PDF](https://wolpertlab.neuroscience.columbia.edu/sites/wolpertlab.neuroscience.columbia.edu/files/content/papers/BlaFriWol99.pdf) | | R2 | Blakemore, Wolpert & Frith, "Central cancellation of self-produced tickle sensation," *Nature Neuroscience* 1(7):635-640 (1998) | **Exists** (full text read, Wolpert lab PDF) | Description source: efference copy; "first robot study" label **contested** (it's an fMRI study that summarizes the robot results) | [doi:10.1038/2870](https://doi.org/10.1038/2870) · [PDF](https://wolpertlab.neuroscience.columbia.edu/sites/wolpertlab.neuroscience.columbia.edu/files/content/papers/BlaWolFri98.pdf) | | R3 | Weiskrantz, Elliott & Darlington, "Preliminary Observations on Tickling Oneself," *Nature* 230:598-599 (1971) | **Exists** (metadata and PubMed record; not read; per R1, a stimulus on the sole of the foot rated less tickly when self-administered) | Description source (no link given); **accurate** as "an earlier study of self-tickling" | [doi:10.1038/230598a0](https://doi.org/10.1038/230598a0) | | R4 | PubMed record for R1 (abstract) | **Exists** (read) | Added: abstract checked against the video | [pubmed.ncbi.nlm.nih.gov](https://pubmed.ncbi.nlm.nih.gov/10511643/) | | R5 | Kilteni & Ehrsson, "Functional Connectivity between the Cerebellum and Somatosensory Areas Implements the Attenuation of Self-Generated Touch," *Journal of Neuroscience* 40(4):894-906 (2020) | **Exists** (abstract read) | Added: later evidence for the cerebellum's role; **accurate** | [doi:10.1523/JNEUROSCI.1732-19.2019](https://doi.org/10.1523/JNEUROSCI.1732-19.2019) | | R6 | Blakemore, Smith, Steel, Johnstone & Frith, "The perception of self-produced sensory stimuli in patients with auditory hallucinations and passivity experiences," *Psychological Medicine* 30(5):1131-1139 (2000) | **Exists** (abstract read) | Added: self-monitoring breakdown; **accurate** | [doi:10.1017/s0033291799002676](https://doi.org/10.1017/s0033291799002676) | | R7 | Wikipedia, "Sarah-Jayne Blakemore" | **Exists** (read) | Added: biography; PhD UCL 2000 | [wikipedia.org](https://en.wikipedia.org/wiki/Sarah-Jayne_Blakemore) | ### Not found or not checked - The Weiskrantz et al. (1971) paper itself wasn't read; its content here comes from R1's summary. - The 1998 *NeuroImage* abstract cited in R2 for the first robot results wasn't checked. - The bug-and-snake examples are the video's illustrations, not from the papers. ## Added context - **Series:** Part 1 of a new "Science" series, the channel's first topic outside evolution, the age of the Earth and logical fallacies. Previous upload: [[Which came first, the chicken or the egg (How evolution works, Part 2)]] (2026-11-08). - **Related:** [[The straw man (Logical Fallacies, Part 1)]] and [[Why are we so mean in the comments]] were the channel's other non-evolution uploads. - **Laughter vs. tickliness:** the 1999 paper notes that why tickling makes us laugh is "of much debate," split between those who see tickle-laughter as purely reflexive and those who see it as social [R1]; the video sidesteps this by talking only about how ticklish touch feels. - **Beyond tickling:** the same "predict and turn down" idea is used to explain why people with certain psychotic symptoms can, unusually, find their own touch about as intense as someone else's [R6]. ## Biographies ### Joel is Curious (the creator) YouTube channel **Joel is Curious**, mostly Shorts, from 2026-10-04. In his own words (video description): "I'm Joel, a software developer and former tech executive who likes to learn stuff. Science, history, Buddhism, Stoicism, and the thinkers behind them." He lists his sources in each description. (Sources: the video and its description.) ### Sarah-Jayne Blakemore (study lead) British neuroscientist (born 1974), professor of psychology and cognitive neuroscience at the University of Cambridge. BA in experimental psychology from Oxford (1996); PhD from University College London (2000), co-supervised by Daniel Wolpert and Chris Frith. Her later research focuses on the adolescent brain; co-author with Uta Frith of *The Learning Brain: Lessons for Education*. (Source: R7.) ### Chris D. Frith and Daniel M. Wolpert (co-authors) Frith was at the Wellcome Department of Cognitive Neurology, UCL, and Wolpert at the Institute of Neurology (Sobell Department), UCL, at the time of the 1998-1999 papers (affiliations as printed in R1 and R2).