A Model Organism Triptych: A Vacanti Mouse, a Ticklish Rat, and A Pain-Free Mouse

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This piece by Darcie DeAngelo, Shimpei Ishiyama, and Julianne Yip is the tenth post in the Emotional Ecologies series edited by Sarah York-Bertram and Jessica DeWitt. In this series, contributors were asked to reflect on what role emotion plays in connecting humans to their environment and more-than-human beings.

Abstract: An imaginary mouse lives without pain. Another mouse, a real one, grows a human ear. Onlookers express disgust, fascination, indignation, and fear at these experiments. Meanwhile, scientists tickle rats. Across space and time, pain and pleasure are powerful analytics in scientific explorations of animals’ emotional lives. But, pain/pleasure, deliberately non-anthropomorphic, limits speculation about animals’ interior states. Take, for example, bioengineers’ efforts to develop a model organism who does not feel pain.1 Such a model of “pain-free animals” would, theoretically, overcome ethical conundrums raised by research involving animals.2 Without pain, what kind of emotional life might animals experience? A pain-free mouse is meant to stop the outcries over beings like the Vacanti mouse. This mouse received his name from a scientist who grew a human ear on his back. When it was removed, Vacanti joked that he “lived out a happy, normal life.”3 Today, a neuroscientist shows rats have ambiguous desires–they like to be tickled but also fear it. Witnessing another rat being tickled induces playful behaviors in the observer rat. Tickling troubles pain/pleasure binaries, suggesting fun as an underappreciated approach to understanding animal emotions. In this triptych montage of speculative fiction and nonfiction pieces, we portray three rodent mini-stories as an “emotional ecology” of laboratory life. These organisms have their own “emotional” lives. We speculate: What is it like to be a Vacanti mouse? A ticklish rat? And what would it be like to be a pain-free mouse?

A Vacanti Mouse

by Darcie DeAngelo

Mice communicate with ultra-sub-sonic sounds.4 They hear and squeak things that humans cannot. A human ear is low-tech compared to a mouse ear. But scientists decided to grow the flimsy piece of cartilage on the back of one mouse. They named him the Vacanti mouse.5

How strange to grow a piece of cartilage in the shape of an inferior ear on the back of him. He moved fine but it must have been a little bit heavier and, when it was growing, maybe he turned and sniffed at it, the way I finger a new mole. From the perspective of efficiency, it would have been better to grow a mouse ear or a mouse nose for a human, if we’re thinking in hybrids. Better to harvest the superior tools from the backs of animals rather than less talented tools.

The Vacanti mouse took the name of the scientist who grew his ear, but even what he was most famous for, an ear, was not quite an ear. In fact, the mouse had on its back a mold of sheep cartilage that had been cultured to fit the shape of an ear. Then, the living ear sculpture was inserted into the mouse who had been from a family of furless, immunocompromised mice.6 These mice were specifically bred so as not to reject things like this grafting. The cartilage grew on its own within the body of the mouse.

This may have made a difference as to how the ear felt to the mouse. Rather than the ear being part of its body, it was more like a graft, a kernel of another’s life that used its blood and skin. An ear fetus. The ear as fetus stretched the back of the mouse’s skin as it grew–the mouse was not growing with the ear. On standard definition television images replayed on YouTube, you can find the Vacanti mouse in the hands of Charles Vacanti himself as he pets its back with gentle fingers, as he is interviewed by celebrity scientists. The Vacanti mouse looks pretty calm for a mouse. He probably knows the scientist’s smell and he doesn’t look unhappy. His nose twitches with curiosity and he has little ears that the light from the overhead fluorescents shine through.

He already hears so much better than a human.

The Vacanti mouse is a mouse with a human ear grown on its back.
Figure 1. Screenshot from “The Vacanti Mouse” newsreel clip, https://www.youtube.com/watch?v=G-ssQHR54YQ.

A Ticklish Rat

by Shimpei Ishiyama

Ticklishness has fascinated great minds such as Aristotle and Charles Darwin for over two millennia. Yet, we still do not know why we laugh when tickled, why some body parts are more ticklish, and why we cannot tickle ourselves. Interestingly, humans are not the only ones to experience ticklishness; it’s also observed in highly social species such as rats.7 When tickled by a familiar person, rats show joyful behaviors such as ultrasonic “laughter” and Freudensprünge – joy jumps.

They frolic. It’s almost as if cartoonists knew that rats could jump for joy before science proved it. Scientists already suspected that people might have observed these joy jumps with their pet rats, too. That’s why they thought to document it. And they felt lucky enough to provoke the giggling, jumping rats.

The rat’s response to tickling depends on their mood; anxious rats tend to be less ticklish.8 In a remarkable display of empathy, rats respond playfully upon witnessing another rat being tickled.9

In a small laboratory arena, a curious rat explores their surroundings and discovers a hole in the wall. The rat soon learns that by poking their nose into the hole, they can initiate a tickling interaction marked by a beep sound. Over time, the rat repetitively pokes the hole, indicating their desire to be tickled. However, the rat also displays behaviors that indicate a kind of refusal. They hesitate in front of the hole, considering whether to initiate the tickling interaction. Once the decision is made to poke, they may immediately run away from the hole or show brief freezing accompanied by distressed calls.10

Like us humans, the curious rat feels ambivalent about tickling.

This seemingly contradictory behavior can be better understood by looking at the playful nature of tickling. Just like children often squirm and giggle while being tickled but still enjoy the experience, rats may experience a mix of pleasure and fear when they choose to be tickled. This combination of opposite emotions, known as ‘Nervenkitzel’ – thrill of fear, may be what makes tickling enjoyable.

The fact that both rats and humans experience ticklishness suggests an evolutionary connection. Studying ticklish rats could help us better understand complex emotions in animals and maybe even shed light on the mystery of ticklishness itself.

A white human hand tickles the belly of a rat that has a white body and a black head.
Figure 2. Photo by Ishiyama and Brecht (2016).

A Pain-Free Mouse11

by Julianne Yip

Pain brought me into this world. Not my mother’s birth pains, as excruciating as they were, but the pain of our family line. The pain of my father being stung, my grandmother’s tail clipped, my uncle’s skin cut, my sister’s organs injected. For generations we have served. For the sake of Science, Medicine, Humanity–even Animality—we have stood in for you and your human family as we bear the brunt of experimentation.

It seems ironic, then, that our utility has bred a peculiar sensitivity to pain. The cold is sharper; smells more noxious; and, to add salt to the wound, we have developed an insensitivity to the very drugs that could alleviate the pains bred into us.12 Inbreeding has turned us into an open-ended nerve that repeats itself down the generations, not so much a family line but a genetic loop. Their pain is mine to relive—and, if my makers’ promises come true, mine to relieve.

For now, though, we’re still a work in progress. Even with bioengineers’ advanced editing tools, there are bugs. I can tolerate more pain, but can’t smell.13 At least, not very well. My smell-sensitive parent-siblings would probably be more comfortable with this change, finally able to brave the reek of fox urine that suddenly invades our enclosure—and just as mysteriously disappears. But not being able to smell also meant that my mother-sister didn’t notice when I fell out of the nest; failed to tuck me back into the curl of her body, let me press against her warm, soft breast. Blind and hungry, I cried out, not knowing why, only that I needed a response. But she didn’t answer. Except for me, the rest of my litter starved to death. The bioengineers aren’t too worried. No smell-ability is just a bug that can be smoothed out; now that DNA has gone digital, it’s just a matter of tweaking my code.14

In the meantime, there is you. Even though you did not make me (or any of the countless other creatures you tend to), you’re responsible for me day-in and day-out. Feeding, cleaning, grooming. I need your help with all of it. It must be difficult to care for me, especially in those early days when I was so small and hungry all the time. You scooped me into your hands and placed a tiny silicone nipple to my mouth to suck, nursing me too many times to count, for countless hours. Cradled in the warm, dry palm of your hand, I felt safe and secure. Even loved.

My expression of thanks falls outside your hearing range. So I nuzzle your finger, which makes you smile. Even though your mentors and colleagues have advised against becoming too attached—after all, this is a world where killing is how you make a living—the deletion of pain in me has made you more sensitive, not less.15 You take painstaking care of us. This means developing a special mouse milk formula for us, finding us warmth and stability in the form of our stronger mouse cousins, trying to anticipate my needs before I can feel the shape of hunger or fear, cold or loneliness.

The problem, you tell your kind, is not my inability to smell. Instead, the problem is the lack of mother-child match-fit.16 Where my mother-sister could not be there for me, you step in. Where I cannot feel, you feel your way towards me until I don’t know where I end and you begin.

Instead of being an instance of something gone wrong, I am a glitch that could rewrite the code.17

Figure 3. Mouse mother. Images generated by Julianne Yip and Craiyon.com.


1 Najjar, Deborah A. “Toward a more ethical animal model in animal research” M Sc Thesis (2018). MIT.

2 Gardner, Renee M., and Alan M. Goldberg. “Pain-free animals: An acceptable refinement.” Jpn Soc Altern Anim Exp 14 (2007): 145-149.

3 “Remember the lab mouse with a human ear on its back? The scientist accused of “playing God” explains his work”. Newsweek. 2017-09-16. Retrieved 2021-07-29.

4 Turner, Jeremy G., Jennifer L. Parrish, Larry F. Hughes, Linda A. Toth, and Donald M. Caspary. “Hearing in laboratory animals: strain differences and nonauditory effects of noise.” Comparative medicine 55, no. 1 (2005): 12-23.

5 Vacanti, J. P. “Tissue engineering and the road to whole organs.” Journal of British Surgery 99, no. 4 (2012): 451-453.

6 Blum, Jamie E., Brandon J. Gheller, Abby Benvie, Martha S. Field, Elena Panizza, Nathaniel M. Vacanti, Daniel Berry, and Anna Thalacker-Mercer. “Pyruvate kinase M2 supports muscle progenitor cell proliferation but is dispensable for skeletal muscle regeneration after injury.” The Journal of Nutrition 151, no. 11 (2021): 3313-3328.

7 Panksepp, J., and Burgdorf, J. (1999). Laughing rats? Playful tickling arouses high frequency ultrasonic chirping in young rodents. In Toward a Science of Consciousness III, S.R. Hameroff, D. Chalmers, and A.W. Kaszniak, eds. (MIT Press), pp. 231–244.

8 Ishiyama, S., and Brecht, M. (2016). Neural correlates of ticklishness in the rat somatosensory cortex. Science 354, 757–760.

9 Kaufmann, L.V., Brecht, M., and Ishiyama, S. (2023). Tickle contagion in the rat somatosensory cortex. iScience, https://doi.org/10.1016/j.isci.2022.105718.

10 Ishiyama S, Kaufmann LV & Brecht M (2019) Behavioral and cortical correlates of self-suppression, anticipation and ambivalence in rat tickling. Current Biology 29: 3153-3164.

11 This short speculative fiction piece is based on my anthropological fieldwork conducted among synthetic biologists in the Sculpting Evolution Group at the MIT Media Lab in 2019 (Yip 2020). There, I encountered a theoretical animal called “inducible pain free mouse”: inspired by consequentialist moral logics, this mouse model organism would genetically encode a drug-activated “switch” that could be activated before conducting any painful procedures including euthanasia (Esvelt 2019; Najjar 2018). In what follows, I contemplate what it is like to be pain-free mouse. As Donna Haraway notes, “animal as workers in labs…are response-able in the same sense as people are” (Haraway 2007: 71). How would pain-free mouse feel? How would pain-free mouse? What does response-ability mean to pain-free mouse? While I draw on actual mouse models (e.g., Najjar 2018; Weiss et al. 2011), the mouse in this piece is purely imaginative.Kevin Esvelt. “When are we obligated to edit wild creatures?” Leaps.org (August 2019): https://leaps.org/when-are-we-obligated-to-edit-wild-creatures/particle-4; Donna Haraway. When Species Meet. (Minneapolis: University of Minnesota, 2007); Devora Najjar. “Towards a more ethical animal model in animal research.” Master’s Thesis. MIT. https://dspace.mit.edu/handle/1721.1/120675; Julianne Yip. “Pain-Free Mouse, being ‘human, and more-than-human ethics.” (September 2020): CASTAC Blog. https://blog.castac.org/2020/09/pain-free-mouse-being-human-and-more-than-human-ethics/.

12 Jeffrey Mogil et al. 1999. “Heritability of nociception I: Responses of 11 inbred mouse strains on 12 measures of nociception.” Pain 80 (1999): 67-82.

13 Jan Weiss et al. “Loss-of-function mutations in sodium channel Nav1.7 cause anosmia.” Nature 472, no. 7342 (April 2011): 186-190. doi:10.1038/nature09975.

14 Beyond their transcription into computers, scientists have argued that DNA is “digital” in that it is composed of finite and discrete genetic units (nucleotides) that encode proteins. Leroy Hood and David Galas. “The digital code of DNA.” Nature 421, no. 6921 (January 2003): 444-8. doi: 10.1038/nature01410.

15 In her ethnography of human-animal relations in experimental lab science, Lesley Sharp notes that, while experimental lab science is typically characterized as an emotionless space, intimate emotional attachments still develop among humans and animals. Lesley Sharp. Animal Ethos: The Morality of Human-Animal Encounters in Experimental Lab Science. (Oakland, CA: University of California Press, 2019).

16 Jacinthe Gingras et al. “Global Nav1.7 Knockout Mice Recapitulate the Phenotype of Human Congenital Indifference to Pain.” Plos One 9, no. 9 (September 2014): 1-14.

17 “Within glitch feminism, glitch is celebrated as a vehicle of refusal, a strategy of nonperformance. (…) In glitch feminism, we look at the notion of glitch-as-error with its genesis in the realm of the machinic and the digital and consider how it can be reapplied to inform the way we see the [Away From Keyboard] world, shaping how we might participate in it toward greater agency for and by ourselves.” Legacy Russell. Glitch Feminism: A Manifesto. (New York, NY: Verso Books, 2020).

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Darcie DeAngelo, Shimpei Ishiyama, and Julianne Yip

Darcie DeAngelo is an assistant professor in the Department of Anthropology at the University of Oklahoma. As an environmental and medical anthropologist trained in visual methods, her work engages with human-nonhuman relations such as the love between landmine detection rats and their handlers, the excitement of dogs and humans as they hunt for rats in cities, and the kinship of humans and their sourdough starters. She also edits the journal, Visual Anthropology Review. Find more of her work here: https://www.darcie-deangelo.com/ │ Shimpei Ishiyama is a Junior Research Group Leader at the University Medical Center of the Johannes Gutenberg-University Mainz, Germany. His research interest is ‘neuroscience of fun’, an underrated but important research topic. In his research group, he studies the brain mechanisms of joyful emotions in tickled rats. │ Julianne Yip is a sociocultural anthropologist who received her training at McGill University. Her research explores how scientific knowledge of things like sea ice, anthropogenic climate change, zoonotic diseases, and synthetic biology decentre, rescale, and recompose what it means to be human today. She enjoys experimenting with multimodal scholarship in the form of speculative fiction and has consulted on arts/ science collaborations like the 360-degree film “Worlds of Ice” directed by Philippe Baylaucq.

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