Hanger reflex

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The hanger reflex is a phenomenon in which light compression of the head by a wire hanger or similar object involuntarily induces head rotation toward the side of compression. It was first reported by Japanese researchers and has been studied for its potential applications in rehabilitation, dystonia therapy, and human–computer interaction.

Contents

Overview

Side view of the hanger reflex HangerReflexSideView.jpg
Side view of the hanger reflex

The hanger reflex refers to an involuntary head rotation that occurs when the temporal region of the head is lightly compressed by the edge of a wire hanger. The movement is considered reflexive or illusory rather than intentional. The phenomenon gained public attention through Japanese television programs and online media, often described as "the head turning automatically when a hanger is placed on it."

Discovery and research history

The phenomenon was first introduced to the public on January 20, 1995, in the Japanese TV program Knight Scoop, as an unusual effect in which "the neck naturally turns when a wire hanger is placed on the head." Systematic scientific reports were later published in the late 2000s by Japanese researcher Hiroyuki Kajimoto of the University of Electro-Communications and his collaborators, who formally named it the hanger reflex. They reported that "compression of the anterolateral temporal region and the contralateral posterolateral occipital region induces head rotation." [1] [2]

Clinical applications of the hanger reflex were initiated by Takeshi Asahi of Kanazawa Neurosurgical Hospital in the late 2000s. [3] Their main concept was to use the reflex to relieve rotational symptoms in patients with spasmodic torticollis (cervical dystonia).

In parallel, applications to human–computer interaction were explored. Devices presenting head rotation sensations through tactile stimulation were proposed in the late 2000s. [4] Subsequent work demonstrated similar effects on other body parts, such as the arms, waist, and cheeks, leading to the development of various hanger-reflex-based haptic devices. [5]

Historically, a very similar phenomenon was first reported by J. E. Christensen, of the Institute of International Health, Immunology and Microbiology, University of Copenhagen, in Denmark, on 31 August 1991, in the scientific article "New treatment of spasmodic torticollis", in the medical journal The Lancet , in connection with treatment for spasmodic torticollis. [6] They used a cardboard box to induce the phenomenon of head rotation; however, the phenomenon that actually occurs is considered to be the hanger reflex itself.

The phenomenon gained attention on social media in 2020 and again in 2022, becoming known as The Hanger Challenge, with people posting videos of the reflex in action. [7] [8]

Mechanisms and hypotheses

The neurophysiological mechanism underlying the hanger reflex remains unclear, but several hypotheses have been proposed:

These hypotheses highlight the interaction between tactile and proprioceptive feedback. In support of the skin-shear hypothesis, studies have shown that lateral stretching of the facial skin alone can induce similar rotational sensations, [9] suggesting that direct pressure is not essential.

If lateral skin displacement is the main cause, one might expect adhesive tapes to produce the same effect; however, typical taping produces opposing shear directions at the start and end points, canceling out the effect. In contrast, compression by a hanger generates consistent shear directions at multiple contact points, avoiding this cancellation.

The hanger reflex is also known to be enhanced by superimposed vibration, [10] [11] though whether this is due to augmented tactile feedback or proprioceptive synergy is not yet clear.

Several neurophysiological studies have been conducted to investigate the mechanisms underlying the hanger reflex. For example, an asymmetric reduction in vestibular response during the hanger reflex has been reported. [12] In addition, electromyographic measurements of neck muscle activity during the hanger reflex have been performed. [13]

Wearing method

Principle of the hanger reflex HangerReflexPrinciple.png
Principle of the hanger reflex

As the effect depends on lateral skin displacement, proper fitting is essential. When using a wire hanger, the long edge of the triangular frame should contact the anterior temporal or frontal region. Because the human head is not perfectly circular, the hanger tends to rotate along the head's longitudinal axis, creating shear on the skin that induces head rotation—toward the right when pressing the right temple, and toward the left when pressing the left temple.

This explains individual variability in susceptibility: individuals with more circular head cross-sections experience weaker effects. It also rules out the "rebound against perceived external force" explanation sometimes seen in media descriptions.

In applied devices, simple wire hangers are rarely used; instead, metal or resin oval rings, sometimes with pneumatic actuation inside, are employed to efficiently generate lateral skin displacement.

Applications

Research on the hanger reflex has extended to medical and engineering applications.

Application to dystonia

Numerous studies have examined the hanger reflex for treating dystonia. [14] [15] [16] Although primarily targeting the neck, a case of runner's dystonia treated with an ankle hanger device has also been reported. [17]

Rehabilitation

Full-body hanger reflex–based systems have been proposed for remote rehabilitation and somatosensory sharing. [18]

Human–computer interfaces

Because the hanger reflex originates from lateral skin shear, it can be induced across the body, leading to numerous HCI applications. In head-mounted displays, it has been used to present haptic head rotation sensations, [19] and to transmit remote users' head rotation sensations intuitively. [20]

Waist-mounted hanger reflex devices have been used for gait control and navigation, [21] [22] and have been adapted to personal mobility control. [23]

Devices applying the reflex to shoulder elevation [24] or elbow rotation [25] have also been developed. Combining the hanger reflex with other modalities, such as electrical muscle stimulation, has been explored for efficient motion instruction. [26]

See also

References

  1. ↑ 佐藤, 未知; 松江, 里佳; 橋本, 悠希; 梶本, 裕之 (2014). "ハンガー反射: 頭部圧迫による頭部回旋反応の条件特定と再現". 日本バーチャルリアリティ学会論文誌. 19. doi:10.18974/tvrsj.19.2_295.
  2. ↑ Matsue, R., Sato, M., Hashimoto, Y., Kajimoto H. (2008) Hanger reflex -a reflex motion of a head by temporal pressure for wearable interface, SICE Annual Conference 2008 Matsue2008
  3. ↑ Asahi, Takashi; Sato, Michi; Nakamura, Takuto; Kon, Yuki; Kajimoto, Hiroyuki; Oyama, Genko; Hayashi, Akito; Tanaka, Kazunori; Nakane, Shunya; Takeshima, Takao; Fujii, Masami; Kuroda, Satoshi (2018). "Pilot Study of a Device to Induce the Hanger Reflex in Patients with Cervical Dystonia". Neurologia Medico-Chirurgica. 58 (5): 206–211. doi:10.2176/nmc.oa.2017-0111. PMC   5958042 . PMID   29607887.
  4. ↑ Sato, Michi; Matsue, Rika; Hashimoto, Yuki; Kajimoto, Hiroyuki (2009). "Development of a head rotation interface by using Hanger Reflex". RO-MAN 2009 - the 18th IEEE International Symposium on Robot and Human Interactive Communication. pp. 534–538. doi:10.1109/ROMAN.2009.5326327. ISBN   978-1-4244-5081-7.
  5. ↑ Nakamura, Takuto; Kuzuoka, Hideaki (2023). "HangerBody: A Haptic Device Using Haptic Illusion for Multiple Parts of Body". SIGGRAPH Asia 2023 Emerging Technologies. pp. 1–2. doi:10.1145/3610541.3614586. ISBN   979-8-4007-0312-6.
  6. ↑ Christensen, JE (1991). "New treatment of spasmodic torticollis?" . Lancet. 338 (573): 573. doi:10.1016/0140-6736(91)91138-K. PMID   1678826. S2CID   29987528.
  7. ↑ "The Hanger Challenge". Know Your Meme. 20 May 2022. Retrieved 21 May 2022.
  8. ↑ "What is the 'Hanger Reflex'? Bizarre New TikTok Trend Explained". 24 May 2022.
  9. ↑ Miyakami, Masahiro; Takahashi, Akifumi; Kajimoto, Hiroyuki (2022). "Head rotation and illusory force sensation by lateral skin stretch on the face". Frontiers in Virtual Reality. 3 930848. doi: 10.3389/frvir.2022.930848 .
  10. ↑ 中村, 拓人; 梶本, 裕之 (2018). "ハンガー反射下の手首への振動重畳による力知覚増強現象". 日本バーチャルリアリティ学会論文誌. 23. doi:10.18974/tvrsj.23.1_35.
  11. ↑ Nakamura, Takuto; Nishimura, Narihiro; Hachisu, Taku; Sato, Michi; Yem, Vibol; Kajimoto, Hiroyuki (2016). "Perceptual Force on the Wrist Under the Hanger Reflex and Vibration". Haptics: Perception, Devices, Control, and Applications. Lecture Notes in Computer Science. Vol. 9774. pp. 462–471. doi:10.1007/978-3-319-42321-0_43. ISBN   978-3-319-42320-3.
  12. ↑ Takahashi, Koji; Johkura, Ken (2022). "Vestibulo-ocular reflex gain changes in the hanger reflex". Journal of the Neurological Sciences. 438 120277. doi:10.1016/j.jns.2022.120277.
  13. ↑ Wang, Dian; Liu, Baoge (2022). "Effects of hanger reflex on the cervical muscular activation and function: A surface electromyography assessment". Frontiers in Physiology. 13 1006179. doi: 10.3389/fphys.2022.1006179 .
  14. ↑ Asahi, Takashi; Nakamura, Takuto; Sato, Michi; Kon, Yuki; Kajimoto, Hiroyuki; Sato, Shuji (2020). "The Hanger Reflex: An Inexpensive and Non-invasive Therapeutic Modality for Dystonia and Neurological Disorders". Neurologia Medico-Chirurgica. 60 (11): 525–530. doi:10.2176/nmc.ra.2020-0156.
  15. ↑ Asahi, Takashi; Sato, Michi; Nakamura, Takuto; Kon, Yuki; Kajimoto, Hiroyuki; Oyama, Genko; Hayashi, Akito; Tanaka, Kazunori; Nakane, Shunya; Takeshima, Takao; Fujii, Masami; Kuroda, Satoshi (2018). "Pilot Study of a Device to Induce the Hanger Reflex in Patients with Cervical Dystonia". Neurologia Medico-Chirurgica. 58 (5): 206–211. doi:10.2176/nmc.oa.2017-0111. PMC   5958042 . PMID   29607887.
  16. ↑ Kohara, Kotaro; Horisawa, Shiro; Kawamata, Takakazu (2024). "Sustainable Improvement of Anterocollis-type Cervical Dystonia with a Hanger Reflex Device: A Case Report". NMC Case Report Journal. 11 2024-0146: 263–266. doi:10.2176/jns-nmc.2024-0146. PMC   11563657 . PMID   39544225.
  17. ↑ Asahi, Takashi; Horisawa, Shiro; Nakamura, Takuto; Kajimoto, Hiroyuki; Takumi, Ichiro (2025). "The Treatment of Runner's Dystonia with Zolpidem and a Device Inducing Hanger Reflex". Cureus. 17 (8) e89749. doi: 10.7759/cureus.89749 . PMC   12421783 . PMID   40937208.
  18. ↑ Ogata, Kunihiro; Nakamura, Takuto; Kanazawa, Shusuke; Nobeshima, Taiki; Kuzuoka, Hideaki; Kurata, Takeshi (2024). "Remote Rehabilitation System Capable of Sharing Somatosensory Sensations". 2024 46th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC). pp. 1–5. doi:10.1109/EMBC53108.2024.10781561. ISBN   979-8-3503-7149-9. PMID   40038979.
  19. ↑ Kon, Yuki; Nakamura, Takuto; Yem, Vibol; Kajimoto, Hiroyuki (2018). "HangerOVER: Mechanism of Controlling the Hanger Reflex Using Air Balloon for HMD Embedded Haptic Display". 2018 IEEE Conference on Virtual Reality and 3D User Interfaces (VR). pp. 609–610. doi:10.1109/VR.2018.8446582. ISBN   978-1-5386-3365-6.
  20. ↑ Li, Wanhui; Nakamura, Takuto; Rekimoto, Jun (2022). "RemoconHanger: Making Head Rotation in Remote Person using the Hanger Reflex". Adjunct Proceedings of the 35th Annual ACM Symposium on User Interface Software and Technology. pp. 1–3. doi:10.1145/3526114.3558700. ISBN   978-1-4503-9321-8.
  21. ↑ 今, 悠気; 中村, 拓人; 梶本, 裕之 (2016). "ハンガー反射の歩行への影響". 日本バーチャルリアリティ学会論文誌. 21. doi:10.18974/tvrsj.21.4_565.
  22. ↑ Kon, Yuki; Nakamura, Takuto; Kajimoto, Hiroyuki (2017). "HangerON: A belt-type human walking controller using the hanger reflex haptic illusion". ACM SIGGRAPH 2017 Emerging Technologies. pp. 1–2. doi:10.1145/3084822.3084833. ISBN   978-1-4503-5012-9.
  23. ↑ Kobayashi, Masato; Kon, Yuki; Zhang, Jianyao; Kajimoto, Hiroyuki (2019). "Hanger Drive: Driver Manipulation System for Self-balancing Transporter Using the Hanger Reflex Haptic Illusion". SIGGRAPH Asia 2019 Emerging Technologies. pp. 15–16. doi:10.1145/3355049.3360521. ISBN   978-1-4503-6942-8.
  24. ↑ Okuda, Kohei; Nakamura, Takuto; Kuzuoka, Hideaki; Yamakoshi, Kohei; Suzuki, Yusuke (2025). "A Method for Upper Body Posture Modification Using Skin Deformation Presentation on the Shoulders". 2025 IEEE World Haptics Conference (WHC). pp. 31–37. doi:10.1109/WHC64065.2025.11123192. ISBN   979-8-3315-3353-3.
  25. ↑ Nakamura, Takuto; Kuzuoka, Hideaki (2024). "Rotational Motion Due to Skin Shear Deformation at Wrist and Elbow". IEEE Transactions on Haptics. 17 (1): 108–115. Bibcode:2024ITHap..17..108N. doi:10.1109/TOH.2024.3362407. PMID   38319766.
  26. ↑ Sakashita, Mose; Hashizume, Satoshi; Ochiai, Yoichi (2019). "Wrist-Mounted Haptic Feedback for Support of Virtual Reality in Combination with Electrical Muscle Stimulation and Hanger Reflex". Human-Computer Interaction. Recognition and Interaction Technologies. Lecture Notes in Computer Science. Vol. 11567. pp. 544–553. doi:10.1007/978-3-030-22643-5_43. ISBN   978-3-030-22642-8.
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